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Author Topic: Light for print viewing  (Read 15596 times)

digitaldog

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Re: Light for print viewing
« Reply #20 on: November 20, 2017, 03:08:02 pm »

I'ld rather let others determine whether my observations on the magenta filtering component in high CRI LED daylight bulbs is useful information.
Oh after the peer review, they will (should). Funny, I didn't mention anything about magenta filtering component in high CRI LED daylight bulbs. Only someone's silly acceptance of marketing hype, with questions that you simply cannot or will not answer for obvious reasons to some here!
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Whether it's high CRI numbers...
You still are unaware that this is a bogus metric and tells us virtually nothing?
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...or some spectrum graph analysis
The correct way to evaluate a superior and useful metric; are you able to do this?
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... really isn't as important as just having enough light to make the brightness of white paper match the brightness of display white.

What a rather broad and ridiculous statement.
You should study this topic a bit more before posting, especially in terms of what paper white, white and white appearance all mean and produce, and sometimes poorly with OBAs and less than ideal lighting.


The reason there's so much ignorance on the subject of color management, is that those who have it are so eager to regularly share it! - The Digital Dog
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Garnick

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Re: Light for print viewing
« Reply #21 on: November 20, 2017, 03:09:29 pm »

If that works for you. I'ld recommend you get it. It's the most accurate to the color rendering characteristics of a sunbeam on the planet.

There's an observation I'ld like to relate here about daylight balanced LED's I'm starting to notice in how they circumvent the green to bluegreen spike in their spectra. And I see it in the photo posted by Garnick's studio setup and in my Hyperikon LED bulbs.

Couple of years ago I bought a 27" LG LED sRGB gamut display that was color calibrated at the factory by a very expensive Minolta Color Analyzer. What I've found in the ensuing years comparing its native white to the high CRI LED 4000K- 5000K bulbs is that the bulb's color of white has a magenta filtering component that attempts to neutralize their green spike. Since it is very difficult for us humans to see the exact color of bright transmissive white on a display it works out pretty well but not as perfect as the Solux.

I just found this out when calibrating/profiling my LED display with the Colormunki Display set to target white balance of D65 which now makes my native white and neutral grays look greenish. I checked the Target D65 profile's vcgt tag (I have a Mac) which shows the red and blue curves equally pulled way down from the top that are making my video card render in a way my supposedly native 6500K white point of my display comply with Xrite's definition of 6500K which is attempting to override the magenta bias of white I can't see on my display.

This could be an alternate method of double profiling due to the appearance of the color of white can be subject to adaptation and thus my native display white, though it was measured at the factory to be 6500K, by setting to target D65 (instead of native) tells the software that the Minolta Color Analyzer definition of 6500K isn't so perfectly neutral.

Not sure but when I see a pattern of manipulation of color with daylight LED bulbs compared to LED backlit displays, it makes me take note. Any PAR30 or PAR20 bulb as on the Lumicrest site will work but find out how much light they put out first because you may need to buy more than one to get it to match the luminance of your bright white LED display which is far more influential in color matching prints.

I'm not that concerned about it because my eyes adapt pretty well to slight variances of white light and any tint that might exist in neutral grays. It's so subtle that it doesn't really drastically change the appearance of memory colors but B&W prints might be slightly off from the display under these LED bulbs.

Just something I discovered about LED daylight bulbs.

Hi Tim,

I just have one question.  What is it exactly what you are seeing in the photo I displayed of my working setup, as mentioned in this sentence - "And I see it in the photo posted by Garnick's studio setup and in my Hyperikon LED bulbs".  Just curious.

Gary
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digitaldog

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Re: Light for print viewing
« Reply #22 on: November 20, 2017, 03:16:25 pm »

I have not looked at that specific LED; got a URL?
Well I see a lot of (more) marketing hype on their site. Can't fine a spectral plot which (to again correct Tim) would tell us a massive amount about the light quality prior to actually buying/seeing the blubs. The talk about CRI; ignore it. Only 8 tiles, the metric was created by the Fluorescent bulb industry to make their numbers look better (much like how projectors use Lumens and those numbers to make you think higher is better; not for photo's!).

8 is too small a set of tiles. That make it easy to create a spectrum that will render the 8-14 tiles and doesn't tell us that the light source is full spectrum. It doesn't tell us how the other colors will render. My understanding is there are two reference sources; Tungsten for warm bulbs and D50 for cool ones: Above and below 4000K. That means that a normal tungsten bulb and perfect daylight both have a CRI of 100! As such, a high CRI is a decent gauge of how well a light will preform in your home but not such a great indicator of how well it will work for photography and proofing. Both a Solux 48 and a "full spectrum" tube from home depot may have a CRI of 97. I can assure you the Home Depot bulb has a giant mercury spike and some spectral dead spots.
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Garnick

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Re: Light for print viewing
« Reply #23 on: November 20, 2017, 03:22:17 pm »

I have not looked at that specific LED; got a URL?

This is the URL I included with my reply to Sharon - http://lumicrest.com/.  I do have the link for the testing information as well but couldn't find it at the moment.  I'll check again later, or perhaps you will find it first.  It's on their site somewhere.

Gary
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Tim Lookingbill

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Re: Light for print viewing
« Reply #24 on: November 20, 2017, 03:31:09 pm »

Hi Tim,

I just have one question.  What is it exactly what you are seeing in the photo I displayed of my working setup, as mentioned in this sentence - "And I see it in the photo posted by Garnick's studio setup and in my Hyperikon LED bulbs".  Just curious.

Gary


I noticed you photo is abnormally quite neutral for most camera AWB or custom WB mechanisms but it is neutral looking except the closer you get to the light source which I took a screengrab indicating the slightly violet blue bias. I get the same thing visually in the Hyperikons but my camera's white balance isn't as good as most cameras. Nikons really force R=G=B and have been the best at AWB.

No manufacturer can perfectly neutralize the oddball spectra of artificial daylight. I'ld say from your posted image yours is very good but I don't know if that's your camera making it look like that.

The point I'm making is sort of questioning who gets to define the look of neutral white light and assign a 'D' or Kelvin designation and call that accurate to some black body radiator seeing all the variances in the definition according to what instrument brand is measuring it.
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digitaldog

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Re: Light for print viewing
« Reply #25 on: November 20, 2017, 03:42:57 pm »

I noticed you photo is abnormally quite neutral for most camera AWB or custom WB mechanisms but it is neutral looking except the closer you get to the light source which I took a screengrab indicating the slightly violet blue bias. I get the same thing visually in the Hyperikons but my camera's white balance isn't as good as most cameras. Nikons really force R=G=B and have been the best at AWB.
So you don't know what bulbs he's using (despite him naming them below), an sRGB Adobe RGB (1998) JPEG upload to a web page is data enough to assume these bulbs are your Hyperikons? Ouch.  :-\
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No manufacturer can perfectly neutralize the oddball spectra of artificial daylight.
Neutralize?
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The point I'm making is sort of questioning who gets to define the look of neutral white light and assign a 'D' or Kelvin designation and call that accurate to some black body radiator seeing all the variances in the definition according to what instrument brand is measuring it
The point I'm making is sort of questioning what you wrote about paper (just having light to make the brightness of white paper match the brightness of display white.) and the idea a display calibrated at the factory is in anyway useful today or over time; questions you cannot answer. So I probably shouldn't have asked you what on Earth you're talking about above. Sorry. :-[
« Last Edit: November 21, 2017, 10:51:37 am by digitaldog »
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Tim Lookingbill

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Re: Light for print viewing
« Reply #26 on: November 20, 2017, 03:47:37 pm »

Clearly what I'm talking about isn't for you, Andrew. Just drop it and move on.
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digitaldog

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Re: Light for print viewing
« Reply #27 on: November 20, 2017, 03:49:05 pm »

Lastly Tim, you need to attempt understand what that Digital Color Meter you've pulled out really tells you!

It's not measuring anything. It is taking two or three bits of information:

1. The color that an app is actually outputting to a pixel. i.e. an RGB level.
2. The colorspace that the app says should be used for that pixel for ColorSync to correctly display it (defaults to sRGB if the app doesn't specify).
3. The ICC profile associated with the display.

Then given those bits of information, it can calculate (via ColorSync) what that particular pixel should be if you were to measure it with an external device, and all of the color transforms, profiles etc. are correct. Since there's much going on here that's not correct, I had to post again. Sorry!


So it is sometimes useful (if you really know what you are doing; big IF) to make sure that all your profiles are in order if you can measure patches with an external sensor.

But it doesn't really do anything to validate anything without an external sensor, other than to verify numbers are what they should be.




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digitaldog

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Re: Light for print viewing
« Reply #28 on: November 20, 2017, 03:50:51 pm »

Clearly what I'm talking about isn't for you, Andrew. Just drop it and move on.
Nor correct. That's why it's not for me. Others besides yourself I can't say. But the peer review/corrections and questions you refuse to answer (for obvious reasons) should be a useful paper trail for those on the fence.  ;)
BTW, excellent job assuming about bulbs here.


If you've only imagined it, you haven't experienced it!

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pearlstreet

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Re: Light for print viewing
« Reply #29 on: November 20, 2017, 03:57:09 pm »

That's the one I have and I can mount it right next to my printer.

Alan

Alan, do use the plano-convex diffuser you can order? I'm not sure if I need that or not.
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Tim Lookingbill

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Re: Light for print viewing
« Reply #30 on: November 20, 2017, 04:11:06 pm »

Measuring instruments should follow close to what the eyes see or else what's the point of calibrating to a standard so we all see the same thing.

Since the Colormunki colormeter wrote my native WB now so way off now into the purple blue regions according to Photoshop's XY numbers (see screengrab), I pulled back the same display gains on the red and blue as it did on target D65/6500K and I still get way off xy color temp measurements at native WB. When the display was new there was no greenish white. In fact I had the RGB gains set to R51,G49,B47 and I got a x, y Kelvin number as read in Photoshop's Color Settings indicating it was near 6700K.

If it is WB drift, why didn't the Colormunki software adjust the vcgt RGB curves to reflect the now purplish white which doesn't look purplish at all?

The curves look the same as they did when white balance measured 6700K native.

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Tim Lookingbill

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Re: Light for print viewing
« Reply #31 on: November 20, 2017, 04:23:36 pm »

I'll answer this issue myself.

These are not precision instruments and neither are the definers of white light for daylight bulbs!

It is dependent on the manufacture and what color of koolaid you want to drink!
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digitaldog

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Re: Light for print viewing
« Reply #32 on: November 20, 2017, 05:14:27 pm »

Measuring instruments should follow close to what the eyes see or else what's the point of calibrating to a standard so we all see the same thing.
Tell us about those instruments you've designed to come up with that concept considering your pervious statements to follow.
Readers should consider the text above and the text below from the same source:
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It is the manipulation of white balance appearance which of course we adapt quite quickly to that is the secret sauce behind selling daylight bulbs including the Solux.
Tell us how such instruments adapt as you admit we do. Oh no, don't; it was a question and you're not one to answer them here (historically today for example).
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I'll answer this issue myself.
But correctly?

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If it is WB drift, why didn't the Colormunki software adjust the vcgt RGB curves to reflect the now purplish white which doesn't look purplish at all?
The WB drift assumption? That is to be added to the other assumptions:
Curves assumption?
CRI assumptions?
Solux assumptions?

The Koolaid for some to drink?
Is display calibration a new process for you?
More question marks that you can't answer; sorry;D
« Last Edit: November 20, 2017, 05:28:49 pm by digitaldog »
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Rand47

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Re: Light for print viewing
« Reply #33 on: November 20, 2017, 05:57:06 pm »

So I'm thinking about the goose neck solux.

http://www.solux.net/cgi-bin/tlistore/clampon.html

Sharon,

I have one of those for "taking my show on the road" and am constantly frustrated with the gooseneck being "too short" to get the lamp head out far enough to get decent coverage of even a 13x19" print.  The other fixture with a longer straight-arm (up to 32") might be a better choice!

And.... I originally got the diffuser to use to make a more even light - which it did - but which also lowered the overall illumination from the single bulb enough to make is not optimal for my purposes. 

Rand
« Last Edit: November 20, 2017, 06:02:30 pm by Rand47 »
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pearlstreet

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Re: Light for print viewing
« Reply #34 on: November 20, 2017, 06:01:07 pm »

Thanks Rand.
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Alan Goldhammer

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Re: Light for print viewing
« Reply #35 on: November 20, 2017, 06:09:48 pm »

Alan, do use the plano-convex diffuser you can order? I'm not sure if I need that or not.
Yes, I use the diffuser.
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pearlstreet

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Re: Light for print viewing
« Reply #36 on: November 20, 2017, 06:21:40 pm »

Thanks, Alan.
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Garnick

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Re: Light for print viewing
« Reply #37 on: November 20, 2017, 09:06:58 pm »


I noticed you photo is abnormally quite neutral for most camera AWB or custom WB mechanisms but it is neutral looking except the closer you get to the light source which I took a screengrab indicating the slightly violet blue bias. I get the same thing visually in the Hyperikons but my camera's white balance isn't as good as most cameras. Nikons really force R=G=B and have been the best at AWB.

No manufacturer can perfectly neutralize the oddball spectra of artificial daylight. I'ld say from your posted image yours is very good but I don't know if that's your camera making it look like that.

The point I'm making is sort of questioning who gets to define the look of neutral white light and assign a 'D' or Kelvin designation and call that accurate to some black body radiator seeing all the variances in the definition according to what instrument brand is measuring it.

Two things Tim.  You seem to think that I did this shot using AWB, which is not the case.  Since the LED Bars are advertised as being 4000K, that's the WB I used for the shot.  Initially I thought you might be taking me to task due to the discrepancy between the green cast shown from the light near the far end of the printer and the foreground area.  That's quite easily explained, since the bulb in that fixture is just a run of the mill "daylight" LED bulb, whereas the LED Bars are obviously much closer to the advertised colour temp.  Either that or the Nikon was just having a good day.  I shot RAW, and the only adjustment was a very slight exposure reduction in Camera Raw, NO colour adjustments.  Also, this was meant to be simply a shot to show Sharon these light bars and how they are installed.  As far as your analysis of the light quality is concerned, I would have to use my imagination to actually see what you have mentioned, on my 27" calibrated and profiled NEC display.  I'm sure you do see what you described, but perhaps only because you were looking for it.  I cannot make any sort of judgement on that Tim.  I can only say that I cannot see what you are apparently seeing.  I can only say that so far I have been very satisfied with the LED Bars and their performance, and my customers are certainly quite satisfied with the results as well.

From this point forward I shall back away and let you and Andrew carry on the battle.  Sorry to say it Tim, but I think you might be losing that one.

Gary         

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Tim Lookingbill

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Re: Light for print viewing
« Reply #38 on: November 20, 2017, 11:10:14 pm »

Two things Tim.  You seem to think that I did this shot using AWB, which is not the case.  Since the LED Bars are advertised as being 4000K, that's the WB I used for the shot.  Initially I thought you might be taking me to task due to the discrepancy between the green cast shown from the light near the far end of the printer and the foreground area.  That's quite easily explained, since the bulb in that fixture is just a run of the mill "daylight" LED bulb, whereas the LED Bars are obviously much closer to the advertised colour temp.  Either that or the Nikon was just having a good day.  I shot RAW, and the only adjustment was a very slight exposure reduction in Camera Raw, NO colour adjustments.  Also, this was meant to be simply a shot to show Sharon these light bars and how they are installed.  As far as your analysis of the light quality is concerned, I would have to use my imagination to actually see what you have mentioned, on my 27" calibrated and profiled NEC display.  I'm sure you do see what you described, but perhaps only because you were looking for it.  I cannot make any sort of judgement on that Tim.  I can only say that I cannot see what you are apparently seeing.  I can only say that so far I have been very satisfied with the LED Bars and their performance, and my customers are certainly quite satisfied with the results as well.

From this point forward I shall back away and let you and Andrew carry on the battle.  Sorry to say it Tim, but I think you might be losing that one.

Gary         

So your photo looks very close to what you're actually seeing in your studio. If so, that's all I wanted to know. I have to say those are some very neutral looking lights. The EXIF data of the posted sample image off your Nikon D610 indicates the white balance was done manually which most likely considers a 4000 Kelvin number setting incamera is a manual setting.

My 4000K Hyperikon spot flood is much warmer than what's depicted in your image which looks closer to my 5000K Hyperikon.

I'm not arguing for the hell of it, Garnick. I'm trying to see any improvements in daylight balanced LED lighting and how Kelvin is being interpreted or filtered for a particular neutral look. Kelvin numbers are just numbers and I'm finding establishing a consistency in appearance in connection with these numbers is darn near impossible across all brands of daylight balanced lighting.

How does cadmium yellow inkjet ink on white paper look under those lights? Maybe you could provide a photo of a color print and it's source image to see how those Lumicrest lights render color. Does cadmium yellow take on a slightly greenish hue to look like lemon yellow?
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digitaldog

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Re: Light for print viewing
« Reply #39 on: November 21, 2017, 10:25:36 am »

So your photo looks very close to what you're actually seeing in your studio.
Is that really a serious question?
This is what his (raw) and our raw really looks like:


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My 4000K Hyperikon spot flood is much warmer than what's depicted in your image which looks closer to my 5000K Hyperikon.
What Spectrophotometer and software did you use to come to that conclusion?
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I'm not arguing for the hell of it, Garnick.
You have yet not argued anything but you have posted some rather suspicious ideas about color. Thankfully Garnick and I'd hope others are onto this concept!
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I'm trying to see any improvements in daylight balanced LED lighting and how Kelvin is being interpreted
That's part of your problem! You don't know how to do so with the proper tools.
When deep in a hole of your own digging: STOP.

Again, SORRY   :o
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