Luminous Landscape Forum

Raw & Post Processing, Printing => Digital Image Processing => Topic started by: hdomke on September 16, 2005, 08:51:40 am

Title: Consensus needed on benefit of 16-bit editing
Post by: hdomke on September 16, 2005, 08:51:40 am
Dan Margulis questions editing Photoshop files using 16-bit in his new book: “Photoshop LAB Color: The Canyon Conundrum and Other Adventures in the Most Powerful Colorspace”

In Chapter Six of the book he argues that even though high bit editing sounds sensible, in practice the theory doesn’t work. On images containing computer generated gradients, yes. But on color photographs, no. “In the last three years, around a dozen people, including me, have made serious efforts to find anything to support the proposition that 16-bit editing might be better under any circumstances. … nobody has found any quality gain at all.”

“At this point the evidence is overwhelming that there is no 16-bit advantage in dealing with color photographs. A few people argue otherwise, but it has now become a matter of religious belief, rather than reliance on demonstrations that they can't provide”.

This is a very important issue for all of us that use Photoshop.  Many of us now keep multi-layered files as 16-bit until we are ready to print. I have 10,000 files like this and I don’t want to double my storage requirements and slow my processing time by using 16-bit unless there is clearly a benefit. We need a definitive answer.

Please offer your opinion and back it up with evidence.
 
Thank you!
Yours truly,
Henry F. Domke
 
Henry Domke Fine Art
www.henrydomke.com
 
I am trying to get you, the experts to agree on this. I am posting this same question to:
Michael Reichmann: www.luminous-landscape.com
Tom Hogan: www.bythom.com
Tim Grey: www.timgrey.com
Adobe Expert Help: www.adobe.com/support/expert_support/main.html
Adobe Photoshop Forum: www.adobe.com/support/forums/main
Ron Galbrith: http://forums.robgalbraith.com (http://forums.robgalbraith.com)
Phil Askey: www.dpreview.com
Bruce Fraser: www.creativepro.com
Stephen Johnson: www.sjphoto.com
Bill Atkinson: www.billatkinson.com
Katrin Eismann: www.photoshopdiva.com
Martin Evening: www.martinevening.com
Andrew Rodney: www.digitaldog.net
Dan Margulis: http://groups.yahoo.com/group/colortheory (http://groups.yahoo.com/group/colortheory)
Title: Consensus needed on benefit of 16-bit editing
Post by: Jonathan Wienke on September 16, 2005, 09:47:18 am
Dan Margulis is a borderline kook on the 16-bit editing issue; his criteria for demonstrating benefit to 16-bit editing are rigged to completely negate the benefits of 16-bit. There are definitely measurable benefits to 16-bit editing; take a look at the simple comparison I did here (http://www.visual-vacations.com/Photography/16_vs_8.htm). You can download the 16-bit source TIFF and the action set I used for the comparison, and verify the difference for yourself. 16-bit editing will not have such a profoundly positive impact on every image, but it will always improve on what you get in 8-bit mode, and will never be worse.
Title: Consensus needed on benefit of 16-bit editing
Post by: jani on September 16, 2005, 09:56:31 am
Henry,

I think you should do these people the courtesy of at least searching this forum for similar, earlier discussions.

We just recently had a discussion thread -- the one Jonathan mentions -- that was debunking Dan Margulis's claims, with photographic evidence to back it up.
Title: Consensus needed on benefit of 16-bit editing
Post by: Jonathan Wienke on September 16, 2005, 10:08:17 am
The one exception is that some threads are gone or at least missing posts; with the recent crash I'm not sure if that particular thread survived. But Andrew Rodney did weigh in strongly disagreeing with Dan's position, which means Dan's statement that "nobody has found any quality gain at all" is either profoundly ignorant or an outright lie.
Title: Consensus needed on benefit of 16-bit editing
Post by: digitaldog on September 16, 2005, 03:12:41 pm
From two posts on the Color Theory list that Dan runs. You can see for yourself in the files I’ve posted. Note that I’ve not heard anything back from Dan now that PS world is over!

On 9/2/05 9:33 PM, "DMargulis@aol.com"  wrote:

DM: "I repeatedly asked him whether he had ever personally run a test (or
seen anyone else perform such a test) where the same exact corrections were
applied in both 8- and 16-bit modes to a real-world color photograph, and
compared

I have such a file which I posted on my site for anyone to download. Unless I’ve suffered a major brain fart (or once again, the rules change), its quite clear to me that the 16-bit file is showing vastly superior quality with respect to noise and artifacts compared to the 8-bit file.

The image  was shot with a Canon 350D (ISO 100). I used Adobe Camera RAW 3.X with all defaults and auto settings OFF. No sharpening in ACR either. The file was brought into Photoshop in 16-bit in ProPhoto RGB from ACR. Then I duplicated the file and converted the dupe to 8-bit. I applied levels corrections (nothing super radical), USM and a boost in saturation (+20 in Hue/Sat). The IDENTICAL corrections were made on the high bit file (hold down option key and the other key command to call levels, USM etc to get exact values) or drag and drop history from one to the other.

Cache is off In histogram. The 8-bit Histo isn’t awful like I see in Bruce’s book. But there is a very noticeable amount of noise in the 8-bit file not seen in the high bit file. I also converted from ProPhoto into LAB and did the same corrections (well not exactly since levels in LAB can’t be duplicated exactly as you would from an RGB file). Again, the 8-bit file shows severe noise introduced by the corrections that simply don’t show up in the high bit file. At 200% zoom, it shows up like a sore thumb.

I’ve taken a section of the image since in high bit, it’s quite large and cropped it down as the 16-bit ProPhoto RGB file. In the zip archive are screen dumps of the corrections made. I also generated a Photoshop action; one duplicates the 16-bit file, converts to 8-bit and applies the three corrections. The 2nd would be used on the original (doesn’t duplicate) making a bit easier to apply both sets of corrections.  After that, zoom into the green (slightly out of focus) bird feeder at 200% and look at the differences. The biggest issues in the 8-bt file appear to show up in shadows which makes sense. This is another reason why even superior quality would be produced on linear encoded data within ACR. It also illustrates the need to “expose to the right” for RAW data since the first 2048 steps of data are all within the first stop of highlights.

This is a real world image and the corrections are not severe and identical on each. The Zip archive is about 1.8mb.

I’m seeing this effect on other files shot and processed in this manner. I can of course supply the RAW data but it’s pretty large. If anyone wants it, let me know and I'll put it on my public idisk.

The file is here:

http://www.digitaldog.net/files/16bitchallange.zip (http://www.digitaldog.net/files/16bitchallange.zip)

Andrew Rodney
Author "Color Management for Photographers"
http://www.digitaldog.net/ (http://www.digitaldog.net/)

Andrew Rodney writes,

>>The image  was shot with a Canon 350D (ISO 100). I used Adobe Camera RAW 3.X
with all defaults and auto settings OFF. No sharpening in ACR either. The
file was brought into Photoshop in 16-bit in ProPhoto RGB from ACR. >>

First of all, thank you for posting it, I agree that it is a real-world
picture with real-world corrections. I have played with it a little bit but won't
have any final comments until I get a chance to manipulate it more, which will
be after Photoshop World. At that time, I will probably take you up on the
offer to provide the raw file, provided you are willing to give me permission to
publish it.

It would not surprise me if this or a similar file containing mostly dull
colors, if left in ProPhoto RGB, would get a better result from 16-bit correction
than 8-bit. I have tested Adobe RGB, ColorMatch RGB, LAB, and sRGB files
enough to be highly doubtful that there are any natural color photographs at all
where the extra bits would be helpful in any real-world context. However, I've
always pointed out that I have *not* extensively tested exotic alternatives, such
as 1.0 gamma files, or ultra-wide gamut RGBs such as ProPhoto. The reasons
they are not tested are 1) they have limited market presence and 2) I strongly recommend against their use in color correction.

I do have another ProPhoto file where 16-bit definitely produced a better
result than 8-bit. However, it was not a real-world exercise in that the file was
intentionally sabotaged in Camera Raw by moving the exposure slider all the
way to the left when the actual final intent was to lighten the file. We did
repeat the same exercise, including the sabotage, with the same file output to
Adobe RGB, and there was no problem with the 8-bit correction.
Title: Consensus needed on benefit of 16-bit editing
Post by: PeterLange on September 17, 2005, 04:12:23 am
Quote

Henry,

Doesn’t your question somehow already contains the answer. If it’s possible to create reasonable synthetic examples, it is / should be just a question of effort to find practical ones.

When you book an 8-bit trip from sRGB to Lab and back to sRGB, this either adds noise or breaks continuous color transitions – depending on the dithering setting in the main color settings tab.  Both effects may not instantly be obvious, however, it just requires some further moves, e.g. increase of contrast or USM with low threshold to make things clear.

Somehow I think that Dan has problem to combine his 8-bit philosophy with his new favorite: Lab.  Whereas such bit precision issues are probably just a side story.  In many cases Lab-edits can be substituted by PS blending modes, Hue / Color / Saturation / Luminosity which offer access to a special version of the HSL color model (where the Luminance axis is computed as a weighted average of R/G/B; which is one reason for the similarity with Lab).  Also I don’t see that anyone (except Bruce Lindbloom) has overcome the in-built hue bending with Lab, which occurs upon changing color saturation in Lab mode.

Anyway, it may be a valid point that 8-bit often are better than expected.  It seems likely to me that Raw converter do not change from 12 to 8 bit unless gamma-encoding is done.  Application of a gamma curve would definitively tear 8 bit shadows apart.  If this assumption about the sequence of happenings is correct, any 8-bit file we receive in PS would already have its 12 bit history...

Cheers! Peter


P.S.: I’d be pleased if you would you like to summarize the results of your survey at the end  .

--
Title: Consensus needed on benefit of 16-bit editing
Post by: LeifG on September 17, 2005, 07:52:58 am
Quote
In Chapter Six of the book he argues that even though high bit editing sounds sensible, in practice the theory doesn’t work. On images containing computer generated gradients, yes. But on color photographs, no.
Henry: In my experience, for well exposed images without extreme highlights and/or shadow detail, there is little advantage to working in 16 bit mode. BUT if you have to make large adjustments (e.g. large midpoint shift in curves) or do contrast masking to bring out shadows, then yes, editing 16 bit mode is essential to avoid posterisation and loss of detail.

16 bit scans from my Minolta 5400 are 200MB. As this is huge, I edit the file in 16 bit mode, then save the finished result in 8 bit mode. Later on if and when I do further (minor) edits, I convert to 16 bit mode again. It prevents posterisation, even though converting to 8 bit mode jettisoned a lot of detail. If I need to do large changes, I rescan to re-generate the original 16 bit file.

You can easily verify this for yourself by editing some images.

Leif
Title: Consensus needed on benefit of 16-bit editing
Post by: Dan Sroka on September 20, 2005, 10:22:32 am
Quote
In my experience, for well exposed images without extreme highlights and/or shadow detail, there is little advantage to working in 16 bit mode. BUT if you have to make large adjustments (e.g. large midpoint shift in curves) or do contrast masking to bring out shadows, then yes, editing 16 bit mode is essential to avoid posterisation and loss of detail.
That sums it up well. You stay in 16-bit to give yourself "room" for editing. I often explain it this way: Imagine you are driving down a road. If you are driving straight, that road can be as narrow as your car, and work perfectly well (8-bit). But if you ever need to make a 3-point turn on that narrow road, you'd get your wheels stuck in the mud. Better to have a wider road (i.e. 16 bit) just in case you need to turn.
Title: Consensus needed on benefit of 16-bit editing
Post by: howard smith on September 20, 2005, 10:27:08 am
I reprocessed some old images in 16-bit instead of 8.  I can see a nice difference in shadows, and in the details on a black tux at a wedding.  On my computer, the execution time was noticable longer, but worth the time.  For me.
Title: Consensus needed on benefit of 16-bit editing
Post by: Mark D Segal on September 20, 2005, 09:39:08 pm
Note: For those of you who received my post of several minutes ago in your inboxes, I have deleted it, because of the remote possibility that there could be a copyright concern regarding an individual's view I mentioned there. This is an edited version with any risk of copyright issues expunged, and my apologies to the person concerned - just in case.

Now to the remaining content of my deleted post:

I believe this is technically a very complex subject, insofar as the more one reads about it, the more one appreciates the possibility that "it depends" - on all kinds of things including how the testing is done. This flavour even comes out on page 133 of Dan's book. He is less doctrinaire about it than some of the discussion would lead one to believe. So the idea that there will be a "consensus" on this issue I think is DOA (dead on arrival).

There is other expert opinion, which you can research, that is more in line with Dan's view of this matter, also based on testing with actual prints, but obviously coming to different conclusions than those of some contributors here.

So when one contrasts these views relative to some very knowledgeable contrary views in this discussion thread, one begins to understand perhaps why I think the highest common denominator of agreement on this issue is likely to be two words: "it depends".
Title: Consensus needed on benefit of 16-bit editing
Post by: Jonathan Wienke on September 20, 2005, 09:56:04 pm
I will go so far as to say that editing in 16-bit mode benefits some images more than others, and the extent of the benefit is directly proportional to the severity of the edits required to get the image into a printable state. With some images, the benefits of 16-bit editing may not show up in a print, but with others, the difference will be very noticeable. And other images will fall somewhere in-between. But 16-bit editing will never have a detrimental impact on image quality; the only drawbacks are increases in file size and edit execution time.
Title: Consensus needed on benefit of 16-bit editing
Post by: Ray on September 20, 2005, 11:00:54 pm
Jonathan,
That sums it up pretty well. I guess with almost automatic everything now available in photography, most of the images that most people take do not require extensive editing and therefore there is likely to be no noticeable benefit editing in 16 bit with images that just require a bit of 'levels' tweaking, hue adjustment and sharpening.

I generally do all editing in 16 bit (if it's available) because I already have enough decisions to make without pondering over the issue of whether or not a particular image is likely to benefit from 16 bit editing. However, none of my computers have less than 2GB of RAM, except my laptop.
Title: Consensus needed on benefit of 16-bit editing
Post by: hdomke on September 21, 2005, 11:17:44 pm
From: Henry F. Domke
www.henrydomke.com

I posed the question of 16 vs. 8-bit editing in Photoshop to a variety of Photoshop experts. I was hoping to get a consensus of the experts and I got it.

Yes to 16-bit editing: 9 experts
No to 16-bit editing: 1 expert -Dan Margulis
Awaiting input: 4 experts

All 9 experts that answered me (Andrew Rodney, Tom Hogan, Adobe Expert Help, Bruce Fraser, Martin Evening, Stephen Johnson, Katrin Eismann, David Biedny, Ron Galbrith) clearly supported 16-bit editing. Most agreed that the benefit was subtle for most photographic images.  Most mentioned the advantage of keeping your options open for the future by using 16-bit since our monitors and printers may one day be better able to show the advantage more clearly.

I could not find a single expert to support Dan Margulis’s comment “At this point the evidence is overwhelming that there is no 16-bit advantage in dealing with color photographs. A few people argue otherwise, but it has now become a matter of religious belief, rather than reliance on demonstrations that they can't provide.” However, I have not heard back from 4 experts Bill Atkinson, Tim Grey, Michael Reichmann and Phil Askey.

What follows are excerpts from the email response I got from each expert.

Andrew Rodney: www.digitaldog.net
Use 16-bit
“I have such a file which I posted on my site for anyone to download. http://www.digitaldog.net/files/16bitchallange.zip (http://www.digitaldog.net/files/16bitchallange.zip)
… its quite clear to me that the 16-bit file is showing vastly superior quality with respect to noise and artifacts compared to the 8-bit file.” “…the 8-bit file shows severe noise introduced by the corrections that simply don’t show up in the high bit file. At 200% zoom, it shows up like a sore thumb.”


Tom Hogan: www.bythom.com
Use 16-bit
“With RAW (and 16-bit data) you are prepared for any future changes in output capability.” “Is Margolis' argument valid? Within a narrow range, yes. If I had control of everything from capture to output, I could imagine an 8-bit editing sequence”


Adobe Expert Help: www.adobe.com/support/expert_support/main.html
Use 16-bit
“The fact that most monitors and printers will only display information in an 8-bit per channel color mode means that the only advantage to maintaining images in 16-bit color is if the images will require processing within Photoshop that affects the entire tonal range of the image.” “if you find you need to apply many adjustments to a single image on a regular basis, 16-bit editing may give you an advantage.”

“16-bit per channel images do have noticeable improvements when working with computer-generated images … and outputting directly to film.”

“In practice, most people may never notice the difference between 8-bit and 16-bit when working with standard photographs. (In much the same way most people will not notice much difference when listening to an audio CD, or an MP3 file--and for the same basic reasons.)”


Bruce Fraser: www.creativepro.com
Use 16-bit
“I've demonstrated many times things that work better in 16-bit than in 8 bit, but Dan has rejected these because they don't fit his narrow criterion of doing exactly the same things to a 16-bit and an 8-bit file, then comparing the results. Bruce Lindbloom has elegantly pointed out the futility of entering into the dispute when the deck is already stacked.”

“If you find the extra bit depth doesn't buy you anything, don't use it. But don't come crying to me years hence when your monitor has a 1000:1 contrast ratio, your outputs are hitting a dMax of 2.8, and all your legacy files are breaking.”

Martin Evening: www.martinevening.com
Use 16-bit
“From a practical viewpoint, yes, once I have an optimised image in 16-bits there is not always a lot of point keeping it in 16-bits, and so I mostly then convert to 8-bit, especially if I am using lots of layers. I don't worry after that. But consider this - what of the future of HDR imaging? … the technology is now emerging to allow us to display images at true 16-bit depth on the new prototype LCD displays of the future.”


Stephen Johnson: www.sjphoto.com
Use 16-bit
“With all due respect to Dan, my experience is quite different.”

Katrin Eismann: www.photoshopdiva.com
Use 16-bit
“Yes, I am a 16 bit person...well actually I’m flash and blood!”

David Biedny http://attentionphotoshoppers.libsyn.com (http://attentionphotoshoppers.libsyn.com)
Use 16-bit
“As in the worlds of pro audio and "film", higher bit depths are important for processing and enhancement, as well as mastering.

With an eye to the future, I feel you have made a wise decision to work in 16 bit. Can't hurt, and storage is cheap.”

Ron Galbrith: http://forums.robgalbraith.com (http://forums.robgalbraith.com)
Use 16-bit
“…for quality work I prep files in 16-bit because I've demonstrated to myself it's useful to do so.”

Bill Atkinson: www.billatkinson.com
No answer yet.

Tim Grey: www.timgrey.com
No answer

Michael Reichmann: www.luminous-landscape.com
No vote yet  “haven’t read the book”

Phil Askey: www.dpreview.com
No answer yet
Title: Consensus needed on benefit of 16-bit editing
Post by: Mark D Segal on September 21, 2005, 11:58:39 pm
You'll find Tim Grey's answer if you are a subscriber to his copyrighted DDQ and have access to the archive.

Did you ask each of the respondents whether they have personally tested this proposition rigorously and conclusively? Anyone who is answering based only on the appearance of histograms shouldn't count, because it is not easy to infer the impact on a print of various patterns of histogram break-up.

By the way, I work in 16 bit also - as an "insurance policy". But I must add, the several photographs I've worked in both showed indistinguishable results. However, they were not photographs needing massive adjustments. I'm not sure how massive an adjustment needs to be before 16 bit really makes a visible difference on a print without a loupe. The experts in testing for this issue should have addressed this matter of the adjustment threshold and can tell us.

I believe Jonathan cut to the chase very succinctly and probably correctly several posts ago. One thing about Dan is that he has extensively worked and tested everything he explains and demonstrates in his published material and seminars, so I have a lot of time for what he says about this stuff, regardless of whether he is a minority of one or several.
Title: Consensus needed on benefit of 16-bit editing
Post by: digitaldog on September 23, 2005, 02:06:48 pm
Dan has finally responded and I’m not surprised that once again, the “rules” of his 16-bit challenge have shifted. I’m not going to post his entire reply but rather mine to his list. Note that NOW, the issue is wide gamut RGB spaces (which he hasn’t defined) but ProPhoto RGB falls into that camp. I’d say LAB certainly does as well but we’ll see what he has to say about that one. The files I posted are there for anyone to examine. I still feel that my Rebel 350 capturing nothing more than a snapshot clearly produced an image outside of Adobe RGB (1998) and I can clearly show that there are output devices such as my Epson 2400 that do as well. High bit editing is about headroom and flexibility but Dan doesn’t see it as an advantage. He questions the use of wide gamut spaces and says only 1% of users are working with such spaces and they are not all that intelligent in doing so. I have no stat’s to back this up nor does he. He doesn’t tell us why using high bit on wide gamut spaces is a problem (other than the file is twice as big) nor the advantages to us in working with a smaller gamut space simply to avoid the noise that presents itself when editing in 8-bit. So I don’t get it! Anywhere, you’ll get the overall idea of what was side from both sides in my response below. For a guy who’s done a lot for the industry and come up with some compelling uses of LAB, I find it hard to side with someone who goes out of his way to hide from the obvious facts seen in just this test and who continues to measure with a rubber ruler.
----------
On 9/23/05 10:54 AM, "DMargulis@aol.com"  wrote:

> I have always made clear that
> exotic RGB definitions, such as 1.0 gamma, or ultra-wide gamut RGBs, are not
> tested because, first, almost nobody uses them, and second, those
> knowledgeable
> about color correction would be unlikely to edit in them except under very
> unusual circumstances.

With all due respect Dan, that’s nonsense. Nobody uses the? The edits here are unusual? Many professional users, many digital photographers use ProPhoto RGB. Every edit in Adobe Camera RAW no matter what color space encoding you select or what bit depth happens in ProPhoto RGB with a 1.0 gamma prior being presented to the user.

I can (and I think did) illustrate that to anyone that wants to examine the image in Adobe Camera RAW, the scene gamut cannot be fully exploited in Adobe RGB (1998) and can in ProPhoto in 16-bit (as it can in 8-bit with obvious appearing noise).

I didn’t expect this scene or any additional scenes I can capture with this sub $1000 camera to “fit” your criteria since once again, that seems to be a moving target. So I’ve come to the conclusion that no matter what one does to try to show the advantage of high bit editing, it will fall on at least two deaf ears. Others who wish to download the image can clearly see for themselves the downside of using 8-bits compared to high bit with the example I posted. They can decide for themselves that there ARE real world, non synthetic images that fall outside Adobe RGB (1998) gamut (as does my $800 Epson 2400) that benefit from high bit editing.

> The error in Andrew's method is in his final step. After the levels and
> Hue/Sat moves, the two versions can't be told apart without great difficulty.
> However, his sharpening settings have a Threshold (noise reduction) of 0. This
> causes a problem specific to ultra-wide gamut RGBs.

Dan, you can see the effect of the noise in the 8-bit version without any USM. NONE was applied in ACR, the image is in serious need of sharpening but none the less, the noise is present without it. More editing will produce a greater effect of showing this. We have no idea what will happen with future editing, conversions to other color spaces for output, resizing etc. As I’ve stated in the past, the use of high bit simply provides more editing headroom. To dismiss the obvious effect of this noise by saying that “this or that edit” isn’t kosher when the edits do not show degradation in the high bit file is simply another effect of sticking one’s head in the sand. This is and has always been the advantage of high bit editing!

> Any file corrected in 8-bit will be very slightly grainier than one corrected
> in 16-bit.

Noiser in shadows with a very odd speckling? Yes, I see that. That’s not a useful attribute to induce on a file unless you want such an effect. It’s not seen on the high bit file.

> (Andrew concedes that
> when these same moves are applied in Adobe RGB, the two images are the same
> for
> all practical purposes).
  
Yes I do, with a significant amount of color information I can use tossed away in the process. It sounds like you’re in favor of using ultra-small gamut RGB working spaces in 8-bit.

Dan, you can apply a Gaussian blur to the image and remove the noise but no one is suggesting this is a good way to remove the noise or smooth out a histogram. Bottom line is one editing routine doesn’t produce this effect of noise, the other does. I want the color available for output without the noise, I can accomplish this in high bit.

> In the ProPhoto version the difference manifests itself in a more
> active-looking 8-bit file. It has more noise in shadow areas, particularly in
> the
> worker's face and in an area of the background. I agree that these things are
> bad.

>> While it's arguable whether the image taken as a whole is better or worse,
>> certainly Andrew is entitled to object to the graininess.

Well I consider that some progress <g>

> It should also be pointed out that the graininess is more a function of the
> ultra-wide gamut RGB than it is of the bit depth.

Indeed it is. The scene and the file require this wide gamut space since I can, will and want to use those colors to the output devices I have available today. In the future, I would expect even wider gamut devices to be at my disposal. Other than the file being twice the size, what’s the problem?

> If you are misguided enough to work in an ultra-wide gamut RGB, that is.  

The same effect can be seen in LAB which is a ultra wide gamut space! I can clearly see similar noise issues in 8-bit LAB versus high bit LAB.

> At bottom, though, it's just another attempt to blow smoke over the inability
> to back up his partners' extravagant claims.
  
Anyone other than Dan taking this statement at face value should consider looking at the RAW file, converting both ways and using whatever corrections they wish. There’s no smoke here. The data is there for anyone to see. But since once again, the rules of this silly challenge have changed, I have to join the ranks of those such as Bruce Lindbloom as someone that finds more smoke in Dan’s challenge than anything else. So know we have to show a difference between the two using what gamut working space?

> "If you correct in 8-bit rather than 16-bit, you are not currently a
> recreational rather than professional user, and you will not currently see a
 >night-and-day, totally-obvious-to-anyone-who-looks difference, but if you > continue to
> do so, in two or three years when ProPhoto RGB is introduced into Photoshop,
> you *will* be a recreational rather than professional user, by God, and you
> *will* see a night-and-day, totally-obvious-to-anyone-who-looks difference,
> unless
> you are one of the 99.9% of users intelligent enough not to attempt major
> edits in an ultra-wide gamut RGB."

I think that quote about recreational users is someone else's however, I still agree that it’s pretty obvious in the current example that there’s a visible and obvious benefit of the high bit editing versus the 8-bit editing. And if you can back up the statement that 99.9% of users do not use ProPhoto RGB, I’d love to see some empirical data to back that up. Once again, you appear to the one blowing smoke by implying you have the “ear of the industry” by saying that less than 1% of users are working in this space. I have no stat’s to provide but I do know of many digital photographers are working in this space. I certainly would not go on record as you have to say it’s a mere 1% and all of them are lacking intelligence.

Once again, I’ve provided empirical data to show that many scenes captured with just a prosumer digital camera fall way outside Adobe RGB (1998) gamut as does a number of Prosumer desktop printers. If those colors are not important to you, fine. The challenge is so undefined and moving that you should really add that the “tests” have to be done in this or that space, using this or that edit, using this or that RAW converter. The effects of the edits on an 8-bit file ARE visible in synthetic images and have always been so but that didn’t wash with you. Now, with a real world image that is basically a snapshot, the issue is the working space. What next?

Andrew Rodney
Author "Color Management for Photographers"
http://www.digitaldog.net/ (http://www.digitaldog.net/)
Title: Consensus needed on benefit of 16-bit editing
Post by: Mark D Segal on September 23, 2005, 02:32:57 pm
Andrew, I had a rough day yesterday so maybe I am a bit myopic today, but I found your post very confusing. Firstly, where do we get access to everything Dan said - i.e. his full response? It would be good to see the whole text. Secondly, there is a co-mingling in your post of two issues: colour spaces and bit depth. Since this is a thread about bit depth, the discussion should stick to that, unless the choice of colour space impacts the bit depth argument - if it does, the specific effect of choice of colour space on 8 ver 16 bit image editing needs to be clarified and its impact on the choice of 8 versus 16 explained - for the benefit of those of us who haven't personally tested all the permutations and combinations.
Title: Consensus needed on benefit of 16-bit editing
Post by: digitaldog on September 23, 2005, 02:37:08 pm
Quote
Andrew, I had a rough day yesterday so maybe I am a bit myopic today, but I found your post very confusing. Firstly, where do we get access to everything Dan said - i.e. his full response? It would be good to see the whole text. Secondly, there is a co-mingling in your post of two issues: colour spaces and bit depth. Since this is a thread about bit depth, the discussion should stick to that, unless the choice of colour space impacts the bit depth argument - if it does, the specific effect of choice of colour space on 8 ver 16 bit image editing needs to be clarified and its impact on the choice of 8 versus 16 explained - for the benefit of those of us who haven't personally tested all the permutations and combinations.
Here’s the entire post. At the bottom you’ll see how you can access it or join his list (bring aspirin):

Prior to my trip to Photoshop World, Andrew Rodney posted a link to an image
as part of his never-ending attempt to explain how his business partners can
say that correcting in 16-bit is what differentiates a professional from a
recreational user, how it creates a night and day difference, how the advantage is
totally obvious to everyone who looks, etc., etc. Lee Varis posted a response
with which I concur, but I did not myself have time to look at the image
closely and said I would do so in future weeks.

As I indicated in my first brief response, the example is meaningless,
because it assumes a condition that I have always excluded, and that wasn't even
known at the time his partners said those things. I have always made clear that
exotic RGB definitions, such as 1.0 gamma, or ultra-wide gamut RGBs, are not
tested because, first, almost nobody uses them, and second, those knowledgeable
about color correction would be unlikely to edit in them except under very
unusual circumstances.

Andrew's test depends on using such a space, an ultra-wide gamut RGB known as
ProPhoto. This space was not installed in Photoshop until 2003, and since his
partners made the remarks about night and day differences and professionals
and recreational users long before that, they cannot possibly have been
referring to it.

The image is an outdoor scene. A laborer, on his knees, is laying a cement
deck or patio. There is greenery and yellow flowers in the foreground; the patio
takes up almost a third of the picture. The laborer is relatively small. His
face is in shadow. The background ground cover is yellowish. On the whole one
would describe the colors as subdued. The picture isn't ridiculously dark but
it certainly needs to be lightened.

Lee Varis correctly characterized such spaces as "like using a sledge hammer
to drive finishing nails". By that, he meant that the are too imprecise to be
used in serious image manipulation, because most of their possible color
values are either well out of any reproduction gamut or totally imaginary. This
image is a perfect example: the large patio is basically gray, however there is a
certain amount of variability, with some parts slightly redder and others
cooler. During the correction process, we need to be sure that these colors don't
get out of hand so that the patio looks like a rainbow rather than cement.
Doing so is no sweat in any rational RGB. We just try to have the three RGB
values be approximately equal throughout the area, understanding that exactly
equal isn't going to happen.

But in an ultra-wide gamut RGB, it's much more difficult, as the values have
to be kept much closer to absolute equality, because colors get brilliant very
rapidly in such a space. Consequently, maintaining neutrality in such an
image during correction is a nasty problem in an ultra-wide gamut RGB and no
problem at all in LAB, CMYK, or a rational RGB.

Because any small variation in an ultra-wide gamut RGBs is actually a huge
variation in output color, the tiny differences between a file prepared in 8-bit
and one in 16-bit are magnified. In realistic RGBs, these differences are so
slight that nobody notices them no matter how much they are affected by later
edits. But in an ultra-wide gamut RGB, it is at least conceivable that certain
images will look better if they are worked on in 8-bit and others will look
better if done in 16-bit.

In Andrew's procedure the image is not edited in Camera Raw, but is exported
to 16-bit ProPhoto. The test calls for making a second copy which is then
converted to 8-bit. Then, to both, one master-channel Levels command is applied,
followed by one increase to master saturation in the Hue/Saturation command,
followed by one unsharp mask filter.

In examining the image, I looked at not just these two variants, but several
others in ProPhoto, as well as 8-bit and 16-bit Adobe RGB using exactly the
same commands, and 8-bit sRGB where I used the same commands but attempted to
strengthen them to match the look of the ProPhoto files.

The error in Andrew's method is in his final step. After the levels and
Hue/Sat moves, the two versions can't be told apart without great difficulty.
However, his sharpening settings have a Threshold (noise reduction) of 0. This
causes a problem specific to ultra-wide gamut RGBs.

Any file corrected in 8-bit will be very slightly grainier than one corrected
in 16-bit. In rational RGBs, this difference is so imperceptible that it
makes no difference in the sharpening process. In an ultra-wide gamut RGB, it can
be seen IF you specifically use a zero threshold. In that case, you will see
two definitely different images, as we do in this case. (Andrew concedes that
when these same moves are applied in Adobe RGB, the two images are the same for
all practical purposes).

In the ProPhoto version the difference manifests itself in a more
active-looking 8-bit file. It has more noise in shadow areas, particularly in the
worker's face and in an area of the background. I agree that these things are bad.
However, it has slightly more believability in the foreground greenery and in
the concrete, which are more prominent items. I believe that this is the reason
that when Lee Varis printed out the two files and showed them to another
observer without explaining which was which, the observer picked the 8-bit version
as being better.

While it's arguable whether the image taken as a whole is better or worse,
certainly Andrew is entitled to object to the graininess. What he is not
entitled to do is, when there are several equivalent ways available with no extra
effort, intentionally choose the one that magnifies the effect that he says he
doesn't like. In the sharpen filter, the Amount and Threshold commands work in
tandem. A higher Threshold slightly diminishes the sharpening effect, and we
compensate by raising the Amount. Minute changes are possible, so that there
are, in effect, many different ways of creating substantially the same effect. By
raising the Threshold even to 1 (although I would choose 2) and adding a
corresponding increase in Amount, the 8-bit and 16-bit images are again q
ualitatively equal regardless of which of the three settings is used for the 16-bit
file. I also experimented with much larger sharpening Amounts with the same
result.

It should also be pointed out that the graininess is more a function of the
ultra-wide gamut RGB than it is of the bit depth. As noted, I did another
version in 8-bit sRGB. It's impossible to duplicate the 16-bit ProPhoto exercise
exactly, as much stronger corrections are required in sRGB to achieve the same
look. But I got as close as I could, including sharpening with a zero
Threshold. The 8-bit sRGB file looked smoother than the one done in 16-bit ProPhoto.

In short, this image does not show an advantage, because the part of it that
Andrew complains about could have been avoided with no extra effort and no
loss in quality. Intentionally choosing an inappropriate sharpening setting is
not a real-world move.

What *would* constitute an advantage? As I indicated in my first post, a list
member showed one. An overly dark image needed to be lightened. However, it
was deliberately sabotaged in Camera Raw by turning the exposure control all
the way down. Then, it was exported into 8- and 16-bit ProPhoto and Adobe RGB,
where simple curves were applied to lighten the image grossly. In Adobe RGB
there was no preference between the two versions. In ProPhoto, however, serious
noise developed in the sky in the 8-bit version that wasn't present in the
16-bit. Now, unlike Andrew's image where it might reasonably be argued that the
8-bit version was *better,* in this one everybody would agree that it was worse,
no question. And, unlike Andrew's image, there was no means of avoiding the
problem in the same number of steps. The 8-bit picture would have to be
corrected further to match the quality of the 16-bit.

The image showing 16-bit superiority isn't real-world because it was
sabotaged in Camera Raw. Andrew's image, which wasn't so sabotaged, doesn't show
superiority. OTOH, it wasn't corrected particularly brutally either. So, I would
have to suspect that it would be possible to find a real-world image that is
somewhere in the middle--that is, no sabotage, but a more extreme correction,
causing clear superiority in the 16-bit version. Similarly, one would expect to
find certain files that would correct better in 8-bit than 16-bit.

If you are misguided enough to work in an ultra-wide gamut RGB, that is.

To summarize: working with actual images is a useful exercise, and we should
thank Andrew for making this one available. It does not actually show an
advantage for 16-bit manipulation in ProPhoto RGB, but in all probability he could
have constructed an image that did if he had worked harder at it. If somebody
wishes to produce such an image, I will be happy to note it parenthetically in
the next edition of Professional Photoshop, but I am not interested in
further testing of ultra-wide gamut RGBs as correction spaces myself, as their
disadvantages are such that their use can be recommended only in highly specialized
situations.

At bottom, though, it's just another attempt to blow smoke over the inability
to back up his partners' extravagant claims. Granted, this time it's not a
histogram or a gradient or a sabotaged image. But still, it requires a certain
revision of the original 2001-2002 claims. Perhaps Andrew will allow us to
revise them: instead of saying that there is a night-and-day, totally obvious to
everyone who looks, professional vs. recreational user difference when
correcting color photographs in 16-bit, we can modify it as follows:

"If you correct in 8-bit rather than 16-bit, you are not currently a
recreational rather than professional user, and you will not currently see a
night-and-day, totally-obvious-to-anyone-who-looks difference, but if you continue to
do so, in two or three years when ProPhoto RGB is introduced into Photoshop,
you *will* be a recreational rather than professional user, by God, and you
*will* see a night-and-day, totally-obvious-to-anyone-who-looks difference, unless
you are one of the 99.9% of users intelligent enough not to attempt major
edits in an ultra-wide gamut RGB."

If Andrew can live with that as a resolution, I certainly can.

Dan Margulis




 
 
 
?
 YAHOO! GROUPS LINKS

 Visit your group "colortheory <http://groups.yahoo.com/group/colortheory> " on the web.
  
 To unsubscribe from this group, send an email to:
  () <mailto:colortheory-unsubscribe@yahoogroups.com?subject=Unsubscribe>
  
 Your use of Yahoo! Groups is subject to the Yahoo! Terms of Service <http://docs.yahoo.com/info/terms/> .
Title: Consensus needed on benefit of 16-bit editing
Post by: digitaldog on September 23, 2005, 02:38:22 pm
Further, bit depth and the gamut of a working space DO have connection. In 8-bit, the wider the space, the farther apart the 256 steps. For a guy who’s proposing LAB, there isn’t much wider a space to work with (True, ProPhoto has blue that falls outside human vision).
Title: Consensus needed on benefit of 16-bit editing
Post by: Mark D Segal on September 23, 2005, 03:06:45 pm
Andrew,

Thanks for citing the entire post. I appreciate it. I shall read it attentively. Yes I did join Dan's list quite a while ago, and didn't need aspirin, but then again I haven't been there very often. Maybe the dosage of the medicine correlates with the dosage of the exposure - but I doubt that - it's just me - I can't get too emotional about any of this. I depend on what I see in my prints and I refuse to get fussed over it. I think there are probably a great many out there like me who haven't seen any readily obvious differences between printed images processed from 8 or 16 bit files but do the latter anyhow for insurance. Storage is cheap, computers are fast, so why not.

And yes - thanks for reminding me - the wider the colour space the longer the distance between levels and logically the greater the risk of posterization. BUT the authority I can't quote (because the information is copyrighted and the permissions insufficiently clear), mentioned that you can shed down TO something like 38 levels per channel before you'd see a difference in the prints (I must say I found this hard to swallow - but the source has considerable professional credibility and would seem to have hard evidence up his sleeve). I expect he made that comment in the context of RGB98 working space, but that wasn't specified in his material. Now if THAT's true, it has some pretty clear inferences for the 8 versus 16 bit editing issue, which was the context of his discourse.
Title: Consensus needed on benefit of 16-bit editing
Post by: Mark D Segal on September 23, 2005, 03:28:31 pm
Andrew, I have now read Dan's entire (cogent and closely reasoned) post carefully; I thank me for suggesting that it be made available and you for doing so. I am now satisfied that there won't be a consensus on 8 versus 16 bit editing and there needn't be one either. People should edit in whatever mode floats their boat. I decided some time ago that 16 versus 8 was not worth the expenditure of valuable additional time trying to prove or disprove and I am now thoroughly reinforced in that decision - but again, that's just me. For others, I'm sure "la lutta continua".
Title: Consensus needed on benefit of 16-bit editing
Post by: digitaldog on September 23, 2005, 03:39:18 pm
Quote
Andrew,

Thanks for citing the entire post. I appreciate it. I shall read it attentively. Yes I did join Dan's list quite a while ago, and didn't need aspirin, but then again I haven't been there very often. Maybe the dosage of the medicine correlates with the dosage of the exposure - but I doubt that - it's just me - I can't get too emotional about any of this. I depend on what I see in my prints and I refuse to get fussed over it. I think there are probably a great many out there like me who haven't seen any readily obvious differences between printed images processed from 8 or 16 bit files but do the latter anyhow for insurance. Storage is cheap, computers are fast, so why not.

And yes - thanks for reminding me - the wider the colour space the longer the distance between levels and logically the greater the risk of posterization. BUT the authority I can't quote (because the information is copyrighted and the permissions insufficiently clear), mentioned that you can shed down TO something like 38 levels per channel before you'd see a difference in the prints (I must say I found this hard to swallow - but the source has considerable professional credibility and would seem to have hard evidence up his sleeve). I expect he made that comment in the context of RGB98 working space, but that wasn't specified in his material. Now if THAT's true, it has some pretty clear inferences for the 8 versus 16 bit editing issue, which was the context of his discourse.
Print to what and after what edits? Again, even agreeing on the 38 levels to all and future output devices, what happens if for some reason, you need to apply other edits or other conversions?

High bit editing is about flexibility and insurance. There are those who do not believe in insurance. I can’t knock them for that. Look how few in New Orleans had flood insurance. Look at those who feel that extended warranties are either good or bad. However, in the case of Dan, I don’t see any debate about the merits of high bit editing on wide gamut color spaces. That wasn’t originally mentioned when years ago, he proposed that no one has been able to illustrate that using the same edits on the same file in high bit would produce superior quality. It’s clear on just this one snapshot that there is less noise in the high bit file. Now that I’ve shown this, the rules have changed whereby we need to now bring the gamut of the working space into the test. I submit that using LAB, his new favorite color space produces the same issues. Considering we’re talking digital capture and not scanned images, and considering in this case I’m working in ACR, I have four options before I even go into LAB (assuming I would even do this). I can either toss a good chunk of color I can user or keep it. If the later, then I either have to work in high bit or I have to accept quality loss. The only downside is a larger file. Given the choice between colors I have and can use with a larger file or tossing away colors and working with a file half the size, I prefer the high bit approach.
Title: Consensus needed on benefit of 16-bit editing
Post by: Mark D Segal on September 23, 2005, 04:42:48 pm
Andrew, I'm with you on the insurance angle - as I mentioned that is the main reason why I, like many others, also do my editing in 16 bit, and I work in ProPhoto. On this latter point though, just yesterday, I came accross a situation (a couple of scanned negatives) where ProPhoto produced mangled skin tones that were difficult to correct in PSCS2, so I re-scanned in RGB98 and they came back to looking very natural - again a case where not one-size-fits-all. Alot of what one does really depends on the characteristics of the image and what one intends to do with it. This discussion has been useful to elucidate some of the finer points about the 8 versus 16 debate - which is likely to carry on, and carry on. Meanwhile, for me it is back to editing my images - in 16 bit  :D Cheers
Title: Consensus needed on benefit of 16-bit editing
Post by: digitaldog on September 23, 2005, 04:47:43 pm
Quote
On this latter point though, just yesterday, I came accross a situation (a couple of scanned negatives) where ProPhoto produced mangled skin tones that were difficult to correct in PSCS2, so I re-scanned in RGB98 and they came back to looking very natural - again a case where not one-size-fits-all.
I can’t understand why the skin would be mangled in one working space versus the other all things being equal. In what way?
Title: Consensus needed on benefit of 16-bit editing
Post by: Mark D Segal on September 23, 2005, 05:08:57 pm
Over-saturated redness. I've made some inquiries and it has been suggested to me that skin tones can be more pleasing in a narrower colour space because of lower gamma resulting in less saturation. Much of my work doesn't involve skin tones, so this was a bit of a shocker; the other stuff - city scapes, archeological sites, monuments, landscapes, etc. do very well in the wider space. That too I use mainly for insurance as it appears that our Epson printers using Ultrachrome and K3 inks can reproduce some colours that are beyond the RGB98 gamut.
Title: Consensus needed on benefit of 16-bit editing
Post by: 61Dynamic on September 23, 2005, 08:02:09 pm
Quote
BUT the authority I can't quote (because the information is copyrighted and the permissions insufficiently clear)
Copyright law does not prevent the ability to quote a passage from a book or other copyrighted writing. Feel free to quote a paragraph or two without fear of legal repercussions; you have a legal right to do so.

Or, at the very least tell us who is this "authority" person is so we can look them up ourselves.

_,,


Well my mind has been made about buying his new book. I never made the connection that the person involved in this particular discussion on 16-bit editing was Dan. Perhaps it's because I didn't care to remember the name of that anti-16-bit goober that Mr. Lindbloom mentioned on his site...

Now that I know these are the same people I can't take any of his advice seriously and I will not be buying his book. It's one thing to do or believe in something that I disagree with but it's something else to be so bull-headed about a subject and out-right refuse anything other than one's own ideas.

Forced ignorance is the greatest form of stupidity. Dan is chalk-full of forced ignorance on this subject which throws into question his ability to think rationally about anything else related and provide sound advice.

Quote
I've made some inquiries and it has been suggested to me that skin tones can be more pleasing in a narrower colour space because of lower gamma resulting in less saturation.

Those suggestions are malarky. I can't see how converting from one space to another can effect skin-tones like you describe unless the color-space conversion was done improperly.
Title: Consensus needed on benefit of 16-bit editing
Post by: Mark D Segal on September 23, 2005, 09:43:54 pm
Daniel, if you have access, go to the archive of Tim Grey's DDQ and you will find a very interesting couple of paragraphs on this issue in the September 1, 2005 email. I am being very cautious about the legal aspects of what I quote because copyrights are usually accompanied by an exception clause, which is missing from this source. The USA is a very litigious society and it's not worth taking any risks, whatever the rights may or may not be.

Re buying Dan's book, it appears to be sold-out, so even if you changed your mind you'll be waiting for it. As I mentioned somewhere, this 8/16 business occupies one page out of 358. I've reached page 150, and I've attended one of Dan's workshops where he presented a small amount of the subject matter covered in the book. Although I also edit my images in 16 bit regardless of what he says, I am very happy that I purchased the book as soon as it was published. It is technically very nuanced and quite deep. There is a considerable amount of meaningful material here on the whys and wherefores of image editing (in paticular colour and luminosity) that I haven't found in any other book on Photoshop and I have a fair number or excellent ones. I believe it's irrational to assume that disagreement with an author on one issue makes the rest of the book somehow suspect. But, each to his own.

Now turning to the colour space question, just to give you the complete picture before you come down too hard on what is malarky, there was NO CONVERSION from one colour space to another. Although I am now 100% digital using a Canon 1Ds, before that I did my colour work using ASA 100 colour negative film. I am now scanning a selection of those legacy negatives so I can make better enlargements than what I get from labs over which I have no control. I have been doing most of my scanning (Minolta DiMage Scan Elite 5400) in ProPhoto RGB colour space because it is said to capture some colours that my Epson 4000 can print, but exceed Adobe RGB98 colour space. On the whole this process has been working very well indeed. However, on a couple of portrait shots, I noticed that the skin tones were flush red while the grey balance was fine both by the numbers and my monitor. I knew the skin tones were wrong because one of the subjects was me and I know what my face looks like; the other was a couple from India and they don't have shocking-red skin. I suspected that perhaps the colour space could be a factor. So I RESCANNED the same negatives in ARGB98, and sure enough the skin tones came back to normal. In a private email I submitted these observations to a highly regarded, well-published authority on digital imaging (not Dan - someone else) and the reply I got is what you are calling malarky. The name of the person doesn't matter, and in fairness I'm not revealing the source, because it was a private exchange and that person did not respond to me with any forethought or intention of being embroiled in controversy. Now that you have more information about the background, more useful would be your take on the reasons why the explanation I got is malarky.
Title: Consensus needed on benefit of 16-bit editing
Post by: Jonathan Wienke on September 24, 2005, 01:14:22 am
Quote
Now turning to the colour space question, just to give you the complete picture before you come down too hard on what is malarky, there was NO CONVERSION from one colour space to another. Although I am now 100% digital using a Canon 1Ds, before that I did my colour work using ASA 100 colour negative film. I am now scanning a selection of those legacy negatives so I can make better enlargements than what I get from labs over which I have no control. I have been doing most of my scanning (Minolta DiMage Scan Elite 5400) in ProPhoto RGB colour space because it is said to capture some colours that my Epson 4000 can print, but exceed Adobe RGB98 colour space.
This is not correct. Regardless of output space selection, you are always doing a color space conversion unless you're merely scanning and assigning a color space to the results. Good scanner software will have a color profile for the film stock you're scanning, and will assign the film profile to the raw scan data, then convert the RGB data from the film profile's color space to the selected destination color space. As long as the scanned colors are in-gamut, the selection of destination space is irrelevant; the output will appear identical in a color-managed appregardless of output space as long as no colors are clipped. But if the choice of output space materially alters the appearance of the image (other than gamut clipping) in a color-managed app like Photoshop, then you've probably got crappy scanner software that is merely taking the raw scan data, applying some sort of cluster-fudging to it, and then applying whatever output profile you select to the resulting RGB data.

There's a simple way to verify what's going on. Scan a frame twice with all settings identical except for the selected output color space. Create an Adobe RGB scan and a ProPhoto scan. Open both images in Photoshop, and apply the ProPhoto profile to the Adobe RGB scan. Compare the Adobe RGB scan (that now has ProPhoto assigned) to the native ProPhoto scan. If they look identical, you have crappy scanner software that doesn't have a freaking clue what color management actually is. If they look noticeably different, something else is screwed up.
Title: Consensus needed on benefit of 16-bit editing
Post by: Ray on September 24, 2005, 02:46:27 am
Quote
So I RESCANNED the same negatives in ARGB98, and sure enough the skin tones came back to normal.
Mark,
I'm confused. Was this before or after you fixed the color management problems you had with SilverFast?

Skin tones are very critical because we are all familiar with them. It's part of the reason I'm scanning some slides twice, once with SilverFast and once with Vuescan, both into the ProPhoto color space. Vuescan sometimes gives me a credible skin tone with one of the two options ticked, restore fading, but an excessivley red skin tone with both options ticked. Silverfast can sometimes have me messing around for ages to get the same affect.

It's quite possible that use of one colour space in preference to another will produce different (global) results if there's something not quite right in the color management chain.
Title: Consensus needed on benefit of 16-bit editing
Post by: Mark D Segal on September 24, 2005, 09:46:56 am
Jonathan - I much appreciate your responding to this issue in the tightly reasoned manner you have; it is an intriguing problem and you have raised additional considerations about it that deserve to be probed. Notwithstanding the advice that I reported here - which under the circumstances I still think is plausible, in the back of my mind I haven't dismissed earlier suspicions that perhaps there may be some colour management issues relating either to the scanner software, the scanner itself or the combination. So let us now drill down a bit more.

It gets a bit difficult to analyse this without knowing more about how the scanner software ACTUALLY works, internally. But the software on the disection table here is Silverfast Ai 6 Studio Edition. This is supposed to be the cat's meow of scanning software (unless you own an Imacon), but sticking with the animal analogy, it is also a dog's breakfast for understanding what it really does, because the documentation is crummy and the interface, to put it politely, is "arcane".

Let us recall that I am scanning colour negative material, and that has limitations for colour management different from positive films. It has an obtuse colour management options page that lets you make the following selections:

(A) Colour Management: (A-1) Internal>Monitor: either None or ICM (Image Colour Matching); (A-2) Internal>Output: RGB, or ICM, or CIE Lab, or CMYK. For A-2 I use RGB. For A-1, I can use None or ICM. ICM yields a much more saturated image on screen. But interestingly, this choice does not affect the RGB colour values. (By the way, I haven't seen, or perhaps missed, where they define what "Internal" means.)

( Profiles for ICM:  (B-1) Internal: The choices are a hodge-podge of colour working spaces, such as RGB98, ProPhoto, Colour Match RGB, etc. I have used either RGB98 or ProPhoto as we discussed earlier, and this is the choice that critically affects values once the image is opened in Photoshop. (B-2) Rendering Intent: it provides the usual suspects; I use Relative Colorimetric.

© Embedded ICC Profiles: Once you select a colour space under B-1 above, this section automatically repeats that selection, but there is a check box to "Embed the ICC profile", which I leave checked because that is what codes the colour space data going into Photoshop.

Now, for dealing with the special case of colour negative film, Silverfast has a module called "Negafix". Negafix allows you to select from a very large number of colour negative films according to what is exactly the film you are using, or comes closest in terms of hue/brightness/saturation on the monitor (mine is very well-calibrated and profiled). Then it allows you to tweak the generic exposure and hue associated with that selection, just in case - like me for example - you are using a brand that doesn't come out bang-on correct for any of their presets. Not explained is how this Negafix module integrates into the scanning workflow - i.e. does it act like a film profile at the outset of the scanning process, or is it converting numbers at the end of the process of generating the image file from scanned data (I guess what you mean by "cluster-fudging").

This is as best a description of the Silverfast colour management system for negatives that I can give you, after having read the Silverfast manual and Taz Tally's SIlverfast book, and Ian Lyon's Silverfast tutorials and watched Lasersoft's crummy Quicktime movies that are supposed to "explain" things. I frankly think there is confusion of concepts in the layout of their whole colour management set-up, and I have told them as much but there has been no reply to that generic complaint. (Be all that as it may, I must say that save for this issue - and one other immediately below - once you mess around enough with the settings and get a combo that works, it works pretty darn well.)

Now Jonathan, the issue of "red" was stuck in my mind for the other matter that I sent you the image snippets about - and I asked myself the very question you are now posing - what if the colours are indeed out of gamut, or put otherwise what if the ProPhoto selection is allowing-in out of gamut colours. So after seeing how much better the skin tones emerged due to a simple switch from ProPhoto to RGB98, I went back to that red/purple issue and rescanned one of those Chinatown red images in RGB98; lo and behold, the red came out tamer and when soft-proofed, there was still alot of toning down with some apparent hue shift toward purplish, but not nearly as bad, and not to the extent of wiping out image detail that happened when switching on soft-proofing with the ProPhoto version. So I think this indicates that there may be a gamut issue at play here affecting both problems. In fact, it may be one and the same problem. It seems that selecting a narrower colour space when dealing with some troublesome colours squeezes the latter into gamut more successfully than can happen once the image is opened in Photoshop with the wider colour space. I'm aware that I'm treading in a bit of an alligator swamp because I don't know all these alligators and their habits as well as would be desirable; so now that you've read in much more glowing detail what I can tell you about the matters you raised, I am very interested in your assessment.
Title: Consensus needed on benefit of 16-bit editing
Post by: Mark D Segal on September 24, 2005, 10:02:58 am
Post-scriptum - those alligators I'm referring to are the ones resident within Silverfast - nothing else!
Title: Consensus needed on benefit of 16-bit editing
Post by: Jonathan Wienke on September 24, 2005, 11:40:57 am
I have a wedding today; I won't really be able to get into this until tomorrow evening. But it is on my to-do list. If you could conduct the experiment I suggested and email me 800 pixelish JPEGs of the Adobe RGB and ProPhoto versions of the scans or post liks to them in this thread (so others could follow along) that would be helpful.
Title: Consensus needed on benefit of 16-bit editing
Post by: Mark D Segal on September 24, 2005, 11:53:21 am
Thanks Jonathan - I'll have to email the images to you, because my ISP won't let me hyperlink posted images to a discussion forum. I apologize to the others, but it is a technical limitation I haven't made time to work around yet. It is becoming more important that I do so.
Title: Consensus needed on benefit of 16-bit editing
Post by: Ray on September 24, 2005, 11:57:33 pm
This is getting a bit off topic, but when you two have sorted out the problems of scanning negatives with SilverFast, you'll let me know won't you  :) .

My first attempts scanning negatives using my Scan Elite 5400ll, put Dimage Scan first, Vuescan second and SilverFast last with regard to ease of use and color accuracy, within a reasonable time frame, of course.

I've since downloaded a more recent version of Vuescan which seems to have addressed a number of issues relating specifically to the 5400ll, and the order has now changed. Vuescan is by far the best, Dimage Scan second for an automatic scan with minimal adjustments and SilverFast last again.

SilverFast's behaviour with negatives is a real puzzle. The prescans are not even in the ball park, not even near the ball park; in a completely different city in fact. There is clearly something seriously wrong here. The film type selections in Negafix seem to have no bearing on reality. They are completely inaccurate.

Reading Ian Lyons tutorial on Negafix, he mentions that the prescans can initially look way off because the crop lines might include the black edges surrounding the frame. Move the crop lines inwards and the color changes. Not so with my setup. Makes no difference to the over all color wherever the crop lines are. I've got no idea if this is another symptom of something seriously wrong, or if it's an improvement in the software to remove yet another pitfall that can confuse the amateur.

Of course, the big features of SilverFast are the numerous ways you can change color and color casts, and Negafix has added yet another range of color and hue adjustments. Given enough time, however bad the prescan may look, one can eventually knock it into shape. However, there's a major problem here, even if you do have the time. How do you really know when the colors are accurate? We can't tell by eyeballing a negative on a light-table.

On the issue of a scan into the ProPhoto color space looking redder than the same scan (with same adjustments) scanned into a smaller gamut color space such as Adobe RGB, this is indeed true with Silverfast and negatives, on my system.

Perhaps this is another clue as to incorrect settings somewhere. It's not just a case of the ARGB scan being less red. The entire color range is less saturated, including the appearance of the prescan, indicating that the 'numbers' have not changed with change of 'profile to embed' in the SilverFast CMS section. I'm getting an ARGB image with ProPhoto numbers. To get it looking right, as I initially edited it, I have to assign the ProPhoto color space in PS.

Nevertheless, whether I'm scanning slides or negatives, the prescan always matches the scanned result very closely, when opened in PS with whatever embedded profile I've specified in CMS.

I'll copy this post to a new thread because it's now way off topic.
Title: Consensus needed on benefit of 16-bit editing
Post by: hdomke on September 26, 2005, 06:46:07 am
Tim Grey responded to my question today so I thought I would add it to the mix. Interestingly he says "yes and no" to high bit editing. Tim puplishes the DDQ Newsletter http://www.timgrey.com/ddq/index.htm (http://www.timgrey.com/ddq/index.htm)

Here are his exact words:
There are two key points I'd like to make here. The first is to agree with Dan that the 16-bit advantage is indeed a benefit in theory for color photographs, and with today's technology there is no visible benefit in the final results. Having said that, I still prefer to optimize images in 16-bit. This is simply because I prefer to maintain as much information in the image as possible, even if that additional information doesn't provide a benefit today. Part of this is philosophical (meaning you could very easily discard the notion), but part of it is practical. The practical side of it is the assumption that at some point in the future, we'll have displays and printers that are actually able to take advantage of high-bit data to produce a difference that improves upon what we see with 8-bit data. For example, I expect that at some point there will be printers available that produce a visually better result from 16-bit data than they do with 8-bit data, and at that point you'll wish that all your images had been optimized and saved in 16-bit. Of course, I could be totally wrong on this assumption about future output capabilities.

So, you're looking for a definitive answer. That answer is that, today, there is no real benefit to saving your color photographic images in 16-bit per channel mode. The only benefit would occur with images that require very significant adjustment, but those images would be the exception, as the adjustments really need to be quite significant for there to be any advantage to 16-bit. I'd still prefer to keep those files in 16-bit mode with all layers intact, especially considering how cheap storage is these days.

Keep in mind that for grayscale images, as discussed in the prior question, there is indeed a benefit to 16-bit. So, while you can get excellent results with most color photographs in 8-bit, for grayscale images it really is important to work in 16-bit if that data is available in the original.

The second point I want to make will actually further erode the notion that you need to work in 16-bit, but I'll mention it anyway. That is, even if you strip out a significant amount of information in an 8-bit image by the adjustments you make, resulting in gaps in the histogram, you may not produce any posterization that is visible in the monitor display or final print. I sometimes do a demonstration with an 8-bit color photograph in some of my workshops, creating a Posterize adjustment layer to demonstrate the results of extreme posterization. I start with the value very high (the maximum is 255) and then gradually work it down, asking the students to tell me when they see evidence of posterization in the projected image. I generally get down to somewhere around 40 or 50 before the first student is able to see any signs at all of posterization, and even then it is only minor. The histogram at that point looks quite ridiculous, but the image still looks like a photo. This demonstrates that you can indeed push an image very far before any image quality problems become evident.

So, it is probably quite clear at this point that for color photographs there's not a strong argument in favor of working in 16-bit mode. I still prefer it, and still recommend it, but this is largely for two reasons. One, it virtually guarantees you can't strip out enough detail to cause posterization problems in the final output, even with significant adjustments, and two, it ensures you are retaining the maximum amount of information in your images that you will hopefully be able to take full advantage of in the future as display and output devices advance. I for one find it hard to believe, especially considering how far we've come over the last five years, that we won't have printers in the future that can achieve a benefit from 16-bit data.
--
Henry Domke

http://www.henrydomke.com/ (http://www.henrydomke.com/)
Title: Consensus needed on benefit of 16-bit editing
Post by: jani on September 26, 2005, 08:03:42 am
Just because he can't afford an EDR display (http://www.tomshardware.com/hardnews/20050923_170519.html), doesn't mean they don't exist.

Okay, okay, this is cheating, but interestingly, it addresses two major problem with today's LCD monitors:

 - Really adjustable brightness
 - How black is black?
Title: Consensus needed on benefit of 16-bit editing
Post by: digitaldog on September 26, 2005, 09:05:35 am
What a wishy-washy answer of Tims. Tell him I said so and he should download my RAW file or at the very least, try working with RAW to wide gamut conversions and see if he still feels the same way. As yet, no one on Dan’s list, Dan included has admitted that the random noise seen in 8-bit and not high bit isn’t the result of the bit depth of the edit. They argue that we are fools to use “ultra-wide” gamut working spaces like ProPhoto or that this or that edit isn’t perfection (we don’t live in a prefect world with prefect Photoshop users). Yet the facts remain that using even minor edits on such a wide gamut file shows quite clearly the benefit of high bit editing.

Andrew Rodney
Author “Color Management for Photographers”
http://www.digitaldog.net/ (http://www.digitaldog.net/)
Title: Consensus needed on benefit of 16-bit editing
Post by: Mark D Segal on September 26, 2005, 10:15:08 am
You tell him you said so, and in the process start reading and representing comprehensively, carefully and objectively what some of your professional peers are saying. Just because you disagree with them isn't a reason to selectively distort arguments.
Title: Consensus needed on benefit of 16-bit editing
Post by: digitaldog on September 26, 2005, 10:17:42 am
Quote
You tell him you said so, and in the process start reading and representing comprehensively, carefully and objectively what some of your professional peers are saying. Just because you disagree with them isn't a reason to selectively distort arguments.
I’m not about to spend $35 to join his list to disagree with him...
Title: Consensus needed on benefit of 16-bit editing
Post by: Mark D Segal on September 26, 2005, 10:58:59 am
That's a cop-out - you don't need to spend 35 bucks to disagree with him. Someone of your standing in the digital imaging community can send him an email, because lesser (but equally parsimonious) mortals have also done it. Based on my experience, for a matter of signficant importance like this he is approachable regardless of whether or not you have paid the entry fee.
Title: Consensus needed on benefit of 16-bit editing
Post by: Mark D Segal on September 26, 2005, 11:07:27 am
Henry, very good that you approached Tim Grey on this. I read the same DDQ and noticed there was also another question on the same subject - that one dealing with greyscale images, and in that case he said there is a tangible benefit using 16 bit mode, for the reasons given.
Title: Consensus needed on benefit of 16-bit editing
Post by: 32BT on September 26, 2005, 11:08:40 am
Sometimes I just don't understand these people.

If you want to know why 16bit editing, or even just "processing" for that matter, is useful, go to a decent High-end Prepress house that handles advertising. Or go to your local car dealership and ask for a brochure.

If the experts admit that 16bit is (very) useful for B&W than it is also very useful for color. How many car ads do you know where the car entirely consists of gradients of a single color. Blue or black for example. How is that different from a B&W photo of the same thing? Sometimes even worse as DigitalDog already points out. Some of these car paints are well outside the press printable colors. Or just silver gray, a popular "color" the past several years.

But even for your every day photography. How many of your images have a subdued clear blue sky that turns from a medium cyan to almost white? I have tons. Shot in 8bit in-camera jpg sRGB. They already show posterisation as is, let alone if I edit them to increase a bit of saturation. Never had that problem??? Gees.

I'm pretty sure those so called experts are only staring at an Epson print every now and then, and probably change the rules to not include prepress. Ever saw a transfer curve for newspaper print or packaging? How much do you need to enlarge a file to turn it into a poster sized ad? I submit the following link for some interesting reading:

http://forums.robgalbraith.com/showthr....e=&vc=1 (http://forums.robgalbraith.com/showthreaded.php?Cat=0&Number=262919&page=&vc=1)

think that is academic? Think poster sized ads of the aforementioned cars...

Want another argument: Convert an image to B&W, a common operation I would think, and suddenly the deltaE76=3 limit becomes less than a half. Referring back to those pesky sky gradients; any photographer will admit that a nice deep, almost black sky usually has their preference. Think about it. Going from a subdued cyan gradient that already shows posterisation, to a dark B&W gradient.

But I'm sure that wasn't part of the rules either. Oh, your client came back to you a year later to run a new campaign with the same images in B&W. Sorry, no can do. Worked in 8bit because some a*****e didn't know what he was talking about.

Uh-oh, now I'm getting mad again, where are my pills... gotta stop the rant, sorry...
<g>
Title: Consensus needed on benefit of 16-bit editing
Post by: Mark D Segal on September 26, 2005, 11:30:47 am
Thanks for stopping the rant - it is to all of our benefit that you did so. Don't pre-judge and dismiss the expertise of an author who has been a pre-press professional for the better part of 35 years and was the first inductee to NAPP's Hall of Fame - one of the most significant marks of peer recognition existing in the international digital imaging community. Also, the fact that JPGs processed in a digicam can posterize is not relevant to the discussion in this thread.
Title: Consensus needed on benefit of 16-bit editing
Post by: digitaldog on September 26, 2005, 11:35:18 am
Quote
That's a cop-out - you don't need to spend 35 bucks to disagree with him. Someone of your standing in the digital imaging community can send him an email, because lesser (but equally parsimonious) mortals have also done it. Based on my experience, for a matter of signficant importance like this he is approachable regardless of whether or not you have paid the entry fee.
Mark, is it just Monday or are you low on happy pills?

I disagree with him; isn’t that clear? I can and did do that without spending $35.

I don’t know Tim, don’t know I’ve ever read anything he’s written. I’ve known Dan and read his writings for at least 12 years, maybe more.

There’s a link to the files I’ve uploaded that anyone who wishes can download and try for the evaluation of high bit editing (including Tim). I don’t have Tim’s email, and whether he tries these files or not is immaterial. My point is and continues to be that based on the text posted, he sounds wishy-washy to me. Thats just a personal opinion. At least Dan is consistent although with the files I uploaded, he’s beginning to at least admit that with wide gamut working spaces, the high bit file DOES show a reduction in noise seen in the 8-bit file.

I don’t see why a Grayscale image would be any different with respect to high bit editing as a color image. If anything, working with a very wide gamut RGB working space is the reason high bit is necessary.
Title: Consensus needed on benefit of 16-bit editing
Post by: digitaldog on September 26, 2005, 11:52:35 am
Quote
Thanks for stopping the rant - it is to all of our benefit that you did so. Don't pre-judge and dismiss the expertise of an author who has been a pre-press professional for the better part of 35 years and was the first inductee to NAPP's Hall of Fame - one of the most significant marks of peer recognition existing in the international digital imaging community. Also, the fact that JPGs processed in a digicam can posterize is not relevant to the discussion in this thread.
When you’ve spent your entire professional career working from high end drum scans going out to a halftone dot using a printing process who’s gamut is pretty small, everything starts to look the same. What Dan is admittedly the best in the business in doing is taking piss poor originals and making them look really good. Some would say this is turd polishing <g>. There are some butt ugly originals and poor scans out there and there are all kinds of users who are far less savvy at editing them than Dan. I’d be shocked if any amount of brutal editing on an 8-bit file would show improvements to such a halftone dot compared to 16-bit. The only disadvantage today of high bit files is they are twice as big as their 8-bit cousin. Go back to Photoshop 7 and prior, that wasn’t the case.

The world is vastly different today, even in the last 3-4 years than when Dan was a Prepress guru. We have $800 ink jet printers that have gamuts vastly larger than press (as well as Adobe RGB (1998)), that produce far more continuous tone output. We have digital capture what doesn’t have a defined color gamut but can clearly capture a huge amount of scene data. We have RAW converters instead of scanners. We’ve seen in just the last 4-5 years how far ink jet technology has come in terms of quality and gamut. God only knows what we’ll be using in 10 years.

High bit editing really only brings one thing to the party; headroom. If you think that is useful compared to the size overhead of files, good, use high bit files. If you don’t or can’t see it on any output device you’ll every use, or if you’re making a catalog of 1000 widgest on a white bkgnd, you probably don’t want your files any bigger than they have to be.

If you’re working in wide gamut working spaces, you might want to look seriously into high bit editing. The debate on the Color Theory list has now evolved from the benefit of high bit files to the need for wide gamut working spaces. Seems Dan is willing to admit the high bit files are better with such spaces and now questions why anyone would want to use ProPhoto RGB. Again, when the output of your device is a press, and all you think about is press output, ProPhoto RGB does seem kind of silly. Someone hand him an Epson 2400 and some nice (non turd) images with some saturation and maybe he’ll see the use of such editing spaces.

Again I have no real opinion of Tim because I really have no idea who he is. I DO know Dan and have enormous respect for him. I find he’s often not very good at forward thinking in terms of issues like color management, high bit editing (although we are making progress since I uploaded my files) and I’m not sure I understand his distaste for Adobe and the Photoshop team. But there’s no question he’s enormously intelligent and well versed in image editing. I wouldn’t have spent the time and bandwidth uploading my files and debating all this with him if I didn’t have such respect for him.

BTW, in person, he’s a very charming and likeable fellow.

As far as being an inductee into NAPP and it’s significance, I’m not sure that has any value other than a marketing vehicle but if you find that impressive, far from me to try and try and convince you otherwise.
Title: Consensus needed on benefit of 16-bit editing
Post by: 61Dynamic on September 26, 2005, 12:01:15 pm
Quote
Thanks for stopping the rant - it is to all of our benefit that you did so. Don't pre-judge and dismiss the expertise of an author who has been a pre-press professional for the better part of 35 years and was the first inductee to NAPP's Hall of Fame - one of the most significant marks of peer recognition existing in the international digital imaging community. Also, the fact that JPGs processed in a digicam can posterize is not relevant to the discussion in this thread.
Didn't he spend most of his time in his career when it was either not possible to edit in 16-bit or at best very difficult?

Just because someone has been called a "expert" or "pro" doesn't make them knowledgeable about everything they talk about.

The benefits of 16-bit/channel editing is easily proven. I'd say Dan is suffering form "New & Scary" syndrome. He learned 8-bit editing and knows 8-bit editing. 16-bit editing is outside his comfort zone and so he reacts irrationally to it much like the people who are freakish over digital vs the film they're used to.

His credentials are irrelevant since he can be quickly disproven.
Title: Consensus needed on benefit of 16-bit editing
Post by: 32BT on September 26, 2005, 12:02:00 pm
Quote
Thanks for stopping the rant - it is to all of our benefit that you did so.
Well, my apologies. The a*****e part was a bad joke on my part.
Title: Consensus needed on benefit of 16-bit editing
Post by: Mark D Segal on September 26, 2005, 12:56:20 pm
Andrew (and Daniel), I have no problems with Monday mornings and I don't need happy pills. There are certain behaviours that get my dander up, so let us leave it at that and revert to the substance about the issue itself and the credentials/experience of the people purporting expertise on these matters.

Tim Grey's email address is <tim@timgrey.com>. It says so on his DDQ which is publicly available on the internet for anyone to read without paying 35 bucks. I'm surprised you don't know who he is. Tim Grey is Imaging Strategist at Microsoft Coporation, published "Color Confidence" (Sybex 2004), co-authored "Real World Digital Photography Second Edition" with Katrin Eismann (peachpit Press 2004), taught at the Lepp Institute of Digital Imaging, contributes to Outdoor Photographer, Digital Photo Pro and PC Photo, and is editor of 'The Digital Image".

I've attended a seminar of Dan Margulis, read his Professional Photoshop book, am reading his LAB book, have read alot of the discussion on his Applied Color Theory website and I simply don't buy the notion that he is sclerotic as you and Daniel imply. There is no question - in my mind anyhow - he is TOTALLY up-to speed on today's printing technologies, researches and tests his subject matter thoroughly before publishing, and understands the subtilities of what Photoshop does and doesn't do like few other people in the business.

It so happens that the benefit of 16 bit editing is NOT easily proven IN PRINTED OUTPUT OF COLOUR IMAGES THAT HAVE HAD 'REAL WORLD' CORRECTIONS APPLIED TO THEM, and that is why there is and has been so much debate about this issue. The fundamentals of this debate are all about testing methodology, test conditions, what one tests for (i.e. all that lies behind the contentious phrase "REAL WORLD") and what are the evaluation criteria. Much of the cross-talk is due to differences of opinion or misunderstandings between highly knowledgeable people in these respects. So it ain't over yet, and there is nothing to be gaineed by disparaging peoples' professional credentials because you have issues with them in respect of these matters.

As for NAPP's Hall of Fame being a marketing device - let us get real - there are so few people to have been honoured in this way, the process is so recent and it is so obscure how such a distinction translates into marketability that this comment cannot be taken seriously. NAPP recognition is a peer review for high distinction in digital imaging THAT HAS ALREADY BEEN EARNED AND RECOGNIZED, period. I have attended several NAPP PhotoshopWorlds and seen the whole explanation of the nomination and award process. If anything, it is a boost to NAPP rather than the other way around, but regardless of the underlying motivation it is meaningful recognition that has to be earned in TODAY'S technical and artistic environment.

The one consensus item I retain from this discussion is that 16 bit editing provides headroom and insurance. That is the reason why I use it too, notwithstanding the views of Dan and Tim about its practical impact on images produced from today's generation of inkjet printers.
Title: Consensus needed on benefit of 16-bit editing
Post by: digitaldog on September 26, 2005, 01:19:03 pm
> I'm surprised you don't know who he is.

I didn't say exactly that. I've never met him or read anything he's written (other than the pasted copy above which isn't that impressive). I know Katrin (quite well, for many years).

> There is no question - in my mind anyhow - he is TOTALLY
> up-to speed on today's printing technologies, researches and tests his >subject matter thoroughly before publishing, and understands the >subtilities of what Photoshop does and doesn't do like few other people in >the business.

I'm glad to hear he's got your confidence there. Since you only appear to occasionally read his list, I should add this quote from a few days back:

DM:
> It would not surprise me if this or a similar file containing mostly dull
> colors, if left in ProPhoto RGB, would get a better result from 16-bit
> correction than 8-bit. I have tested Adobe RGB, ColorMatch RGB, LAB, and >sRGB files enough to be highly doubtful that there are any natural color >photographs at all where the extra bits would be helpful in any real-world >context. However, I've always pointed out that I have *not* extensively >tested exotic alternatives, such as 1.0 gamma files, or ultra-wide gamut >RGBs such as ProPhoto. The reasons they are not tested are 1) they have >limited market presence and 2) I strongly recommend against their use in >color correction.

So apparently wide gamut spaces (or spaces outside those listed above) are not on his radar. He also posted:

DM:
> As I indicated in my first brief response, the example is meaningless,
> because it assumes a condition that I have always excluded, and that wasn't
> even
> known at the time his partners said those things. I have always made clear
> that exotic RGB definitions, such as 1.0 gamma, or ultra-wide gamut RGBs, >are not tested because, first, almost nobody uses them, and second, those >knowledgeable about color correction would be unlikely to edit in them >except under very unusual circumstances.  To summarize: working with >actual images is a useful exercise, and we should thank Andrew for making >this one available. It does not actually show an
>advantage for 16-bit manipulation in ProPhoto RGB, but in all probability he >could have constructed an image that did if he had worked harder at it.

So these spaces are exotic and thus not worthy of his testing. Can you see why I'm not so sure he's really pushing the envelope in examining all the issues here?

> It so happens that the benefit of 16 bit editing is NOT easily proven IN
> PRINTED OUTPUT OF COLOUR IMAGES THAT HAVE HAD 'REAL WORLD' >CORRECTIONS APPLIED TO THEM, and that is why there is and has been so > much debate about this  issue.

Sure it is, I've done it and so you can you.

 >The fundamentals of this debate are all about testing methodology, test
> conditions, what one tests for (i.e. all that lies behind the contentious
> phrase "REAL WORLD") and what are the evaluation criteria.

The $800 desktop printer I have here that shows both the usefulness of high gamut working spaces and high bit gamut illustrate this to my eye. Are you sure Dan's done the same?

> So it ain't over yet, and there
> is nothing to be gaineed by disparaging peoples' professional credentials
> because you have issues with them in respect of these matters.

Disparaging? How? I think I made it clear how I feel about Dan.

> As for NAPP's Hall of Fame being a marketing device - let us get real - >there are so few people to have been honoured in this way, the process is >so recent and it is so obscure how such a distinction translates into >marketability that this comment cannot be taken seriously.

Well it appears those who present at these shows are so honoured. But I take the Marxist approach to this. In this case, Groucho that is (you know the old saying about joining a club that would have him as a member). Before you jump all over this, keep in mind I wrote for years for NAPP and have just finished two articles for them. So I have nothing against them whatsoever.

That Dan was the first to be introduced into this club you’re so impressed with has no bearing on the points I’ve raised here.

> The one consensus item I retain from this discussion is that 16 bit editing
> provides headroom and insurance.

That's all I've ever said. I'll add however that large gamut working spaces necessitate high bit editing unless you like the noise and other issues that can result by working in only 8-bit. However, most editing can and should be done (in this example) in the RAW converter which is working not only in high bit but in a linear encoded gamma. However, the bottom line is it appears that after years of Dan saying that no real world image exhibits any advantages of high bit editing, I've at least proven that this isn't so.
Title: Consensus needed on benefit of 16-bit editing
Post by: Mark D Segal on September 26, 2005, 01:52:03 pm
Andrew, Re knowing Tim, you did say exactly that several posts above, quote: "I don’t know Tim, don’t know I’ve ever read anything he’s written."

You say you were not being disparaging - fine, maybe I have a different take from you on what allegations one can make about someone elses' professional expertise before they become disparaging. Let it rest.

I have read exactly the same material you just quoted from Dan. What this boils down to is cross-talk about whether using ProPhoto colour space is a "REAL WORLD" condition. He says he strongly discourages image editing in ProPhoto so for him it is not a "real world" condition, (whereas many other photographers recommend it). That you observe an 8 bit editing issue in this colour space and he hasn't tested for that condition  means there is nothing to argue about here - between the two of you - at least until he tries it himself and comes to a different conclusion, if he would. As for me, instead of getting into the testing fray, which takes alot of time if one does it thoroughly and properly, I find it much easier just to buy the insurance (i.e. edit in 16) and be done with it. So in that regard you and I and many others are on the same wavelength! Basta.
Title: Consensus needed on benefit of 16-bit editing
Post by: digitaldog on September 26, 2005, 02:13:43 pm
Quote
Andrew, Re knowing Tim, you did say exactly that several posts above, quote: "I don’t know Tim, don’t know I’ve ever read anything he’s written."

You say you were not being disparaging - fine, maybe I have a different take from you on what allegations one can make about someone elses' professional expertise before they become disparaging. Let it rest.

I have read exactly the same material you just quoted from Dan. What this boils down to is cross-talk about whether using ProPhoto colour space is a "REAL WORLD" condition. He says he strongly discourages image editing in ProPhoto so for him it is not a "real world" condition, (whereas many other photographers recommend it). That you observe an 8 bit editing issue in this colour space and he hasn't tested for that condition  means there is nothing to argue about here - between the two of you - at least until he tries it himself and comes to a different conclusion, if he would. As for me, instead of getting into the testing fray, which takes alot of time if one does it thoroughly and properly, I find it much easier just to buy the insurance (i.e. edit in 16) and be done with it. So in that regard you and I and many others are on the same wavelength! Basta.
You’re beginning to force me into taking happy pills.

I don’t know Tim, never read anything he’s written, don’t know him from Job. OK, I don’t think I can be any clearer. If he’s so inclined (or you are) to download the files and see if that does or doesn’t change your minds about high bit editing, cool. If not, cool. This all went back to “you can tell him” meaning, if you or anyone else wants to send him the URL to the files, fine. In fact, the original statement wasn’t directed at you.

As for cross talk and ProPhoto, it’s basically a smoke screen of Dan’s to keep from admitting that yes, there are real world images that show the benefits of high bit editing. “Oh, but not a file in this or that color space I’ve not tested“ (and you can see, he’s hardly pushed the envelope in looking at those spaces) and “those edits are not really appropriate”.

Then the cross talk was set to bypass the fact that indeed high bit editing did show benefit to “wide gamut spaces that only odd clueless users are working with”. I expect at some point, the “rules” of this challenge will once again shift as that has been the case over the years. Did you ever read color scientist and guru Bruce Lindblooms take on this challange?

Dan Margulis' 16-bit Challenge: What's behind the controversy?
http://brucelindbloom.com/DanMargulis.html (http://brucelindbloom.com/DanMargulis.html)

This is at least several years old.

I wonder why all of a sudden Dan’s not hip to wide gamut spaces (is it just ProPhoto? He doesn’t define what he means by wide gamut). Could it be that there’s a compelling reason to use high bit with such spaces? Odd that the gamut of my $800 Epson exceeds the gamut or Adobe RGB (1998) and ProPhoto doesn’t.

Bottom line. Wide gamut spaces are useful for some. That’s one point. Point 2, using high bit editing on such spaces reduces or eliminates degradation using such spaces in REAL WORLD IMAGES that shows up in 8-bit editing. That puts to rest in my mind the mideset that high bit editing is all smoke and mirrors. You or anyone that wishes can see this with either my files or with a slew of digital capture devices.
Title: Consensus needed on benefit of 16-bit editing
Post by: Mark D Segal on September 26, 2005, 03:38:23 pm
Andrew, of course I read the whole Lindbloom/Margulis debate a long time ago. My interest in this question is that like many others I want to know what I should do to maximize image quality, and I try to do my homework.

I think you and I would agree there is no point arguing about an issue that one party has tested and the other hasn't; but that much said, I sense from what you selected and quoted from Dan, he may not think your testing passes muster. This goes back to my earlier comment about the fundamentals. In these circumstances it remains an open issue between you and him, notwithstanding that you have tested this and come to certain conclusions which I personally have no basis for disputing. But I'm not about to question Dan's motives for not "extensively" testing 8/16 in ProPhoto, because I'm not a mind-reader.

And neither of us need happy pills  :D. By dialogue one hones into the issues, better understands them, better sees where to take it to the next level, and none of it needs to be personalized. Cheers.
Title: Consensus needed on benefit of 16-bit editing
Post by: PeterLange on September 26, 2005, 04:52:55 pm
Quote from: MarkDS,Sep. 26 2005,15:38
 
Well Mark,

I'd have some fancy theories, too. Best is, I'll post them and ask everyone to prove the opposite.

Seriously, when you are a well known author such as Dan, the burden is solely at his side to release an article which not only explains the thoughts, but also proves everything in a way which makes clear that "you" (Dan) would also have accepted the opposite result.

Is there such an article?

Peter

--
Title: Consensus needed on benefit of 16-bit editing
Post by: Mark D Segal on September 26, 2005, 06:14:49 pm
Peter, interested to see what you will post, but it would be good if the theories were complemented with demonstrated comparative results from applying both the theory and its counterfactual, otherwise it is not possible to understand their practical importance. This may sound pedestrian, but in this business it is inescapable - and it would put you under the same obligation you mention for other authors in your second paragraph. In that regard, as far as I know, what we have so far from Dan are two books, the articles he has written for Electronic Publishing magazine, and his Colour Theory Archive on the Internet.
Title: Consensus needed on benefit of 16-bit editing
Post by: 61Dynamic on September 26, 2005, 06:28:41 pm
Well, I reckon this thread has run its course. At least for me it has. The same points can only be hammered so many times.

So with that, I leave you all with an image which sums up my part in this thread nicely:


(http://dynamicartwork.com/tmp/eject-thread.jpg)

Have fun.
Title: Consensus needed on benefit of 16-bit editing
Post by: vaz on September 26, 2005, 06:58:16 pm
i think this may be related to the above. as a nonpro, does doing as much editing in raw as you can really cause less image quality degradation in the final result, vs same adjustments in ps, and does it make a difference if the raw adjustments are done in 16 vs 8 bits?
Title: Consensus needed on benefit of 16-bit editing
Post by: digitaldog on September 26, 2005, 07:01:51 pm
Quote
i think this may be related to the above. as a nonpro, does doing as much editing in raw as you can really cause less image quality degradation in the final result, vs same adjustments in ps, and does it make a difference if the raw adjustments are done in 16 vs 8 bits?
At least with most converters, all corrections are happing in high bit, not 8-bit. Another advantage is it’s all done on what is known as linear encoded gamma. This can be especially useful when dealing with edits in highlight areas.

It makes a lot more sense to do as much correction at the RAW conversion stage as you can (globally). It’s a lot faster and it’s far less damaging.
Title: Consensus needed on benefit of 16-bit editing
Post by: Mark D Segal on September 26, 2005, 07:03:12 pm
Daniel, was that image of a break-up edited in 8 or 16?  :D
Title: Consensus needed on benefit of 16-bit editing
Post by: 61Dynamic on September 26, 2005, 07:05:42 pm
Quote
i think this may be related to the above. as a nonpro, does doing as much editing in raw as you can really cause less image quality degradation in the final result, vs same adjustments in ps, and does it make a difference if the raw adjustments are done in 16 vs 8 bits?
Ok, my ejector seat is slow.

First part, yes. The more done in Raw, the less degradation you'll encounter. Look at WB as the most obvious example of that.

Second: raw data cannot be adjusted in 8-bit/channel. It is impossible. Any and all raw settings adjustments are done in 16-bit/channel (or more accurately either 12-bit/channel or 14-bit/channel). When you choose 8-bit/chjannel or 16-bit/channel you are just setting what the output image will be.

Quote
Daniel, was that image of a break-up edited in 8 or 16?
8-bit. Duh, look at the posterizeation!  :D
Title: Consensus needed on benefit of 16-bit editing
Post by: Mark D Segal on September 26, 2005, 09:27:52 pm
Turns out this topic has quite a pedigree including some of the "usual suspects" now active on this thread:

Applied\" target=\"_blank\"][a href=\"http://www.ledet.com/marguli...\" target=\"_blank\"]http://www.ledet.com/marguli... (http://www.ledet.com/margulis/ACT_postings/ColorCorrection/ACT-more-16bit.htm[a href=\"http://www.ledet.com/margulis/ACT_postings/ColorCorrection/ACT-more-16bit.htm). Theory[/a]

See especially a long post in that thread by Jim Rich.

One gap in this discussion is any mention of the working space issue and how it may affect the comparative results.