Luminous Landscape Forum

Raw & Post Processing, Printing => Capture One Q&A => Topic started by: narikin on July 19, 2013, 04:59:31 PM

Title: Using 'Linear Response' curve rather than 'Film Standard' in C1 ?
Post by: narikin on July 19, 2013, 04:59:31 PM
I read a few replies here referring to the improved results of using 'Linear Response' in the curve choice, rather than 'Film Standard'

Can someone outline the improvements of this - is it beneficial to all image types, or some more than others? - and run through a brief workflow to set it up as a 'style' and apply it?  I understand you'd need to shoot a test show of the Xrite color checker (can do that) but then what do you do with that shot?

Thanks in advance,
Title: Re: Using 'Linear Response' curve rather than 'Film Standard' in C1 ?
Post by: BartvanderWolf on July 20, 2013, 10:51:05 AM
I read a few replies here referring to the improved results of using 'Linear Response' in the curve choice, rather than 'Film Standard'

Can someone outline the improvements of this - is it beneficial to all image types, or some more than others?

Hi,

The Film Standard curve that is applied by usual default, produces an image with similar characteristics to what film does, it has (amongst others) a highlight roll-off somewhat like the shoulder of the film H&D curve does. To achieve that, the highlights get progressively more compressed (lower contrast) as one approaches the brightest highlights of an image.

While that may help to avoid sudden clipping of highlights, e.g. a sun disk in a bright sunset sky turning (hopefully white) with a sharp edge, it also will take the life out of e.g. very bright clouds near that sun. Assuming one has exposed correctly for the highlights, and there is some detail in bright image areas, it is IMHO usually better to not make those highlights which still do have detail, looking dull and having low contrast. To that end, one uses a Linear curve instead, and the images keep looking crisp.

An unfortunate by-product of the way that the Film tonecurve is implemented in Capture One, is that it shows correctly exposed (ETTR) images, without clipping, as being clipped and seemingly overexposed by about one stop for some camera Raws. Correcting that requires reducing the exposure control which darkens the entire image below what the scene is supposed to look like.

Quote
- and run through a brief workflow to set it up as a 'style' and apply it?

Once you have the Linear response selected for an image, and other settings you always end up making for a certain type of images (e.g. noise reduction only for High ISO shots), you can save (a selection of) those settings as a User defined Style which you can later recall with a few mouse clicks, or even set one as a default. Just make sure to only include those settings in a Style that you actually want to have changed by selecting that Style when you e.g. switch between Styles.

Quote
I understand you'd need to shoot a test show of the Xrite color checker (can do that) but then what do you do with that shot?

No, that's a requirement for Lightroom/ACR, not Capture One.

Cheers,
Bart
Title: Re: Using 'Linear Response' curve rather than 'Film Standard' in C1 ?
Post by: narikin on July 20, 2013, 11:13:12 AM
Thanks Bart,  very useful info.

So - from this are you saying that 'Linear' is really most/only useful when there is (e.g.) a sky image with lots of highlight detail that's got squashed out by 'Film'?  and by implication, other images that are mostly mid-tones, its of less benefit?

And... you also seem to imply that one should not trust the IQ capture histogram, when ETTR with a sky image (e.g.) as that shows a squashed/compressed highlight, which is not accurate, and will lead to underexposure?  I do see that images that are 'correctly' exposed according to the histogram on back of my IQ, are a full stop darker if I switch to 'Linear Response' when on my desktop in C1.  Unfortunately you can't choose to have a linear response histogram on your back display (I think?) Therefore, your only choice is to guess on the overexposure amount, or work tethered and choose Linear in C1 on your laptop, using that histogram to assess exposure, and ignore what the back histogram says.

 

Title: Re: Using 'Linear Response' curve rather than 'Film Standard' in C1 ?
Post by: BartvanderWolf on July 20, 2013, 11:27:36 AM
Thanks Bart,  very useful info.

So - from this are you saying that 'Linear' is really most/only useful when there is (e.g.) a sky image with lots of highlight detail that's got squashed out by 'Film'?  and by implication, other images that are mostly mid-tones, its of less benefit?

Hi,

When there are few highlights, but that must be dark dull images (black cat in a coal mine?), then there is not much difference, although similar things can happen in the deep shadows. I personally dislike the highlight rendering of the film curve so much that I've not studied the shadows in detail.

Quote
And... you also seem to imply that one should not trust the IQ capture histogram, when ETTR with a sky image (e.g.) as that shows a squashed/compressed highlight, which is not accurate, and will lead to underexposure?  I do see that images that are 'correctly' exposed according to the histogram on back of my IQ, are a full stop darker if I switch to 'Linear Response' when on my desktop in C1.

That's because the Phase One backs generally underexpose, to protect the highlights (and with a Film curve in mind). To put it differently, their actual ISO is lower than indicated, at least for some models, One would have to check on DxOmark.com if that also applies for a specific model.

Cheers,
Bart
Title: Re: Using 'Linear Response' curve rather than 'Film Standard' in C1 ?
Post by: narikin on July 20, 2013, 11:48:41 AM
When there are few highlights, but that must be dark dull images (black cat in a coal mine?), then there is not much difference, although similar things can happen in the deep shadows. I personally dislike the highlight rendering of the film curve so much that I've not studied the shadows in detail.

well, not black cats in coal mines (!) but I was just thinking of images of some trees/greenery with no sky, where other than the odd specular detail, 99% of the tonal range is in the middle, especially if made under diffuse daylight.

Not all images have a 'full' tonal range, and it is, imho, wrong to stretch them out and force that, when its not the situation. Flat lighting can be very good sometimes!
Title: Re: Using 'Linear Response' curve rather than 'Film Standard' in C1 ?
Post by: ErikKaffehr on July 20, 2013, 11:59:30 AM
Hi,

I agree with Bart, by I don't think P1 backs underexpose a lot. What I do is to check my images with RawDigger, and I feel that histogram and blinking highlights are helpful for ETTR exposure. I also think "film curve" is misleading.

I have about a month of experience with a P45+, so I need to admit that I am not really experienced. I also would say I prefer Lightroom so far.

Best regards
Erik
Title: Re: Using 'Linear Response' curve rather than 'Film Standard' in C1 ?
Post by: bjanes on July 20, 2013, 01:03:52 PM
Hi,

I agree with Bart, by I don't think P1 backs underexpose a lot. What I do is to check my images with RawDigger, and I feel that histogram and blinking highlights are helpful for ETTR exposure. I also think "film curve" is misleading.

I have about a month of experience with a P45+, so I need to admit that I am not really experienced. I also would say I prefer Lightroom so far.

Best regards
Erik

Erik,

The DXO ISO data confirm your impression. The P45+ is an "ISO less" camera in that the camera gain above ISO does not change with increased ISO settings on the camera. The measured ISO with the camera set at 100 is spot on. The ISO handling of the IQ180 is entirely different, and the camera does underexpose since the measured ISO is considerably less than the nominal ISO set on the camera.

My personal opinion is that the camera and software should stick to ISO standards. This also applies to LR/ACR where an exposure offset is used. With the Nikon D3, the offset is +0.5 EV and this complicates evaluation of exposure according to the the LR/ACR histograms. The same applies to automatic highlight protection in LR/ACR, which appears analogous to the C1 film setting. These objections would be overcome by the provision of a switch for raw histograms both on the camera and in the software.

Regards,

Bill
Title: Re: Using 'Linear Response' curve rather than 'Film Standard' in C1 ?
Post by: Vladimirovich on July 20, 2013, 01:14:37 PM
With the Nikon D3, the offset is +0.5 EV and this complicates evaluation of exposure according to the the LR/ACR histograms.
with ACR/LR nowadays hidden exposure correction is defined by 2 components : what is hardcoded in LR/AC (to find out convert raw to DNG and check the tag) + what is coded in a specific .dcp camera profile selected... so hidden exposure correction = sum of those two numbers... and it changes (might change) based on which .dcp camera profile you select (for Nikons there are > 1 "OEM emulation" profiles from Adobe, in addition to Adobe Standard)
Title: Re: Using 'Linear Response' curve rather than 'Film Standard' in C1 ?
Post by: BartvanderWolf on July 20, 2013, 01:24:39 PM
well, not black cats in coal mines (!) but I was just thinking of images of some trees/greenery with no sky, where other than the odd specular detail, 99% of the tonal range is in the middle, especially if made under diffuse daylight.

Not all images have a 'full' tonal range, and it is, imho, wrong to stretch them out and force that, when its not the situation. Flat lighting can be very good sometimes!

Ah, but that depends on whether the output from Capture One should be the final product, or an intermediate for further processing in e.g. Photoshop. Once you process the file with few remaining highlights, all other tones will not be optimally separated for further processing either. On the other hand, if the full tonescale is used, the intermediate tones will be well separated and further processing has a perfect foundation to work from.

A recent plug-in from Topaz Labs, named Clarity, proves once more how useful it is to have a full tone scale without compressed tones. Each and every different level in the full tonescale can be adjusted. The end product can then have the midtones reduced to below average brightness, but they will have an enourmous amount of detail (should that be the goal). Once it's compressed into a single brightness level, there is little possibility left to use or rescue it.

Cheers,
Bart
Title: Re: Using 'Linear Response' curve rather than 'Film Standard' in C1 ?
Post by: bjanes on July 20, 2013, 05:32:54 PM
with ACR/LR nowadays hidden exposure correction is defined by 2 components : what is hardcoded in LR/AC (to find out convert raw to DNG and check the tag) + what is coded in a specific .dcp camera profile selected... so hidden exposure correction = sum of those two numbers... and it changes (might change) based on which .dcp camera profile you select (for Nikons there are > 1 "OEM emulation" profiles from Adobe, in addition to Adobe Standard)

I am aware of the BaselineExposure tag in the DNG specification, but what is the name of this second tag you mentioned, as listed in the spec?

Regards,

Bill

Title: Re: Using 'Linear Response' curve rather than 'Film Standard' in C1 ?
Post by: Vladimirovich on July 20, 2013, 05:48:23 PM
I am aware of the BaselineExposure tag in the DNG specification, but what is the name of this second tag you mentioned, as listed in the spec?

1) BaselineExposure = hardcoded for all cameras in ACR/LR code (and recorded in DNG when raw is converted by Adobe software)

2) BaselineExposureOffset = either set in .dcp camera profile or zero if absent

hidden exposure correction = BaselineExposure + BaselineExposureOffset

PS: that is also the way to have expocorrections in ACR/LR "beyond" the UI limits - just create one more profile with proper negative or positive BaselineExposureOffset tag.
Title: Re: Using 'Linear Response' curve rather than 'Film Standard' in C1 ?
Post by: Paul2660 on July 20, 2013, 06:45:12 PM
For all Phase files I still prefer the output from Capture one.  As many have pointed out, the film curve seems to apply almost 1/2  stop of expsoure.  You can see this as the thumbnails are being loaded by C1 as each will load darker and then increase in brightness as it's processed by C1.

With the P45+, this always tended to cause the hightlights to blow out, and often I would use the liner curve.  However with the P65+ / IQ60 there is considerably more headroom on the hightlights and shadows.  Most times you can regain most of the cloud details as Bart mentions, with the highlight tool.  With C1 vr 7 both the highlight and shadow tools are very powerful.

I always found the P45+ to be very unforgiving on highlights, and tended to bracket most shots.  When I switched to the IQ160, I was pleased to see that there was considerly more headroom for highlights.  The DxO mark scores on the P45+ and P65 reflected this very well.

With the IQ160 files I rarely use the linear curve as I prefer the look of the film curve and only go liner when I have a situation with hightlights that can't be recovered easliy. 

LR loads the files without the exposure push, but I still find the output from C1 more to my overall liking.

Paul Caldwell
Title: Re: Using 'Linear Response' curve rather than 'Film Standard' in C1 ?
Post by: bjanes on July 21, 2013, 10:17:58 AM
1) BaselineExposure = hardcoded for all cameras in ACR/LR code (and recorded in DNG when raw is converted by Adobe software)

2) BaselineExposureOffset = either set in .dcp camera profile or zero if absent

hidden exposure correction = BaselineExposure + BaselineExposureOffset

PS: that is also the way to have expocorrections in ACR/LR "beyond" the UI limits - just create one more profile with proper negative or positive BaselineExposureOffset tag.

Thanks, that is useful information. In looking at the DNG file EXIF for my D800e, there is no BaselineExposureOffset. Perhaps that is because no profile using a DCP exposure adjustment was in play.

Bill
Title: Re: Using 'Linear Response' curve rather than 'Film Standard' in C1 ?
Post by: Vladimirovich on July 21, 2013, 12:04:04 PM
Thanks, that is useful information.

it is all in DNG spec 1.4

In looking at the DNG file EXIF for my D800e, there is no BaselineExposureOffset. Perhaps that is because no profile using a DCP exposure adjustment was in play.

BaselineExposureOffset intended to be in .dcp camera profiles, so the only way you can have that in .dng file is to have a .dcp camera profile embedded in .dng with that tag

for example :

BaselineExposure: +0.35 in .dng (straight conversion from .nef to .dng using Adobe's DNG Converter)
BaselineExposureOffset: -0.35 in .dcp (D800e Camera Neutral from Adobe - dump using Sandy Mc' dcptool)

now if you will embed that .dcp camera profile into .dng (with ACR for example) you shall see both tags there... otherwise it will be just BaselineExposure (I'd assume because Adobe's DNG converter in a default situation will use Adobe Standard and if it has BaselineExposureOffset = 0 (absent) then it will not embed that tag) ...



Title: Re: Using 'Linear Response' curve rather than 'Film Standard' in C1 ?
Post by: torger on September 26, 2013, 03:11:15 PM
I think the whole film-curve thing is rubbish :). It's about hiding how digital photography works from users, and I think users are able to learn the technical aspects of digital photography and should not need to have a program that emulates film.

I prefer the way RawTherapee works, the only highlight "magic" that takes place is desaturation to the whitepoint at clipping, and clip point is set to first channel clip (usually green). On top of that possibility to enable various modes of highlight reconstruction to move the clip point past the first channel clip and reconstruct the remaining clipped information. And if you want a highlight compression/rolloff you either use a slider (called highlight recovery amount in RT, as what is does is to compress highlights down below clipping when exposure is pushed), or simply just compress the top of your tonecurve.

Both Capture One and Lightroom does so many hidden things hidden away in the background that I almost feel insulted ;), and I also think this way of designing digital photography software has impaired the general understanding of digital photography among users.
Title: Re: Using 'Linear Response' curve rather than 'Film Standard' in C1 ?
Post by: narikin on November 03, 2013, 05:07:59 PM
Just to revive this topic a bit: might I ask - does anyone here have a default/standardized curve file they could share (as a *.copreset) for getting us non-experts into the ballpark when using Linear Response?  

I have had a few attempts, but don't feel particularly amazed by my abilities.  The skies/highlights sure look better, but the mid and shadows seem to suffer.  A good standardized curve for Linear Response would be a terrific starting point.  I appreciate it would still need adjusting, but a move into the right area would be great.

It seems like something Phase should put in there, as a preset choice.  Come to think of it, considering all the weird/esoteric choices they do add as presets, its kind of surprising this is not built in.

Title: Re: Using 'Linear Response' curve rather than 'Film Standard' in C1 ?
Post by: Hening Bettermann on November 03, 2013, 07:12:29 PM
Hei Narikin,

I am not a C1 user, but as I have understood it, the linear 'curve' in general is an intermediate product, and the definite tone curve will depend on the individual image and your vision of it. So a standard curve sounds like a self-contradiction. The linear rendition IS the point of departure you are looking for.

Good light - Hening
Title: Re: Using 'Linear Response' curve rather than 'Film Standard' in C1 ?
Post by: Phil Indeblanc on November 03, 2013, 10:21:34 PM
I tend to agree with you Torger.

It ISN'T film, get over trying to emulate it. New rules new ways of working. Even ISO can be revamped with different sensetivity based on color, and noise levels in the mix.

Maybe it's a way for the software brands and programmers to "hide" how they get the results in developing the file?
 I tried RT. I don't think I gave it enough time, but I haven't tried it since. What the other apps like LR or C1 do is suggest how they can be used and how it will apply. This can be very helpful when working with new apps.

Things are not broke, so there is no need to change much, but I think there can be some things better explained due to the way sensors work, and no need to bridge it with film.
Title: Re: Using 'Linear Response' curve rather than 'Film Standard' in C1 ?
Post by: rhadorn on December 02, 2013, 10:02:27 AM

I am using the linear curve a lot. According to a recent post on the C1 blog, the standard curve simulates the old color slide, which reproduced only about 8 EV - much less than what present cameras are capable of.

I nevertheless experienced some difficulties in the reproduction of colours. Saturation goes back with contrast and can obviously not be simply compensated by raising the contrast slider. Raising contrast with the contrast slider can lead to some weird colours. So, using the linear development curve, I run into new constraints.

Since the HDR sliders have been improved (Version 7 I think), I make more often use of them instead of the linear curve. The original saturation in the midrange is preserved and it seems that the correction algorithm of the highlights and shadows sliders handles colors intelligently.

This being said, I would be very pleased if C1 gave some additional options besides the choice of a development curve, for example, a linear curve with color correction. It is not written in stone that the raw developer can only produce bright and well defined colors with the so called standard curve.


Reto
Title: Re: Using 'Linear Response' curve rather than 'Film Standard' in C1 ?
Post by: allegretto on December 02, 2013, 03:54:22 PM
Am currently taking the LULA C1 Course

In about lesson 10 or 11 or so, Michael and David explain the "linear" is the actual RAW file curve. The Others, "film standard" are curved renditions of the RAW
Title: Re: Using 'Linear Response' curve rather than 'Film Standard' in C1 ?
Post by: allegretto on December 05, 2013, 11:20:00 AM
one more thing...

C1 also provides an "Auto" correction to any curve you like. Perhaps some could see if it's the stepping off point they desire. One could use Auto and then modify it to suit their general tastes and save that as their stepping off point as well

I find Auto amps exposure a bit more than I like (esily corrected though). However it is my understanding that Auto isn't a constant, but rather varies with the input... but I'm not sure on that
Title: Re: Using 'Linear Response' curve rather than 'Film Standard' in C1 ?
Post by: rhadorn on December 05, 2013, 03:51:28 PM
Thank you for your suggestions.

In a blog entry at C1, I read that a gamma curve is also applied to obtain the so called linear rendition. So this one is not linear in the sense of the original distribution of tone levels from the sensor. Unfortunately, that blog entry does not say more about it. I suppose that the curve they call linear is calculated so as to cancel the long shoulder and the small foot of the standard curve ('S' shape), intended at imitating the good ol' slide. Stretching the S reduces contrast of the mid-tones and this is what impacts the colors themselves, hue as well as saturation.

As to the support the automatic adjustment may give, I made a simple test, applying the auto adjustment for the standard and the linear rendition to the same picture. Contrast and saturation are corrected to the same extent, only the exposure varies, actually pushing to the highlights, as you observed yourself. Sorry, the highlights slider slips also a bit more right with the standard curve. I purpously slected a picture with overexposed sunlit clouds.

Reto
Title: Re: Using 'Linear Response' curve rather than 'Film Standard' in C1 ?
Post by: allegretto on December 05, 2013, 04:20:12 PM
Not sure where David is but I know he can help

IIRC, he said it's "linear" because it is the RAW sensor's output. All others are actually "curves" which is why they look as we are used to seeing them. They even went into discussing that some houses now limit to starting with "linear" since it is pure

In any case, the LULA course is great. There is so much to the software. The program is so rich and modifiable vs LR. Even Michael seemed impressed at some points. I'm sure he can answer our question as well...

Thank you for your suggestions.

In a blog entry at C1, I read that a gamma curve is also applied to obtain the so called linear rendition. So this one is not linear in the sense of the original distribution of tone levels from the sensor. Unfortunately, that blog entry does not say more about it. I suppose that the curve they call linear is calculated so as to cancel the long shoulder and the small foot of the standard curve ('S' shape), intended at imitating the good ol' slide. Stretching the S reduces contrast of the mid-tones and this is what impacts the colors themselves, hue as well as saturation.

As to the support the automatic adjustment may give, I made a simple test, applying the auto adjustment for the standard and the linear rendition to the same picture. Contrast and saturation are corrected to the same extent, only the exposure varies, actually pushing to the highlights, as you observed yourself. Sorry, the highlights slider slips also a bit more right with the standard curve. I purpously slected a picture with overexposed sunlit clouds.

Reto
Title: Re: Using 'Linear Response' curve rather than 'Film Standard' in C1 ?
Post by: narikin on December 08, 2013, 09:52:17 AM
Am currently taking the LULA C1 Course

In about lesson 10 or 11 or so, Michael and David explain the "linear" is the actual RAW file curve. The Others, "film standard" are curved renditions of the RAW

How's the LuLa course?  I know and have used C1Pro for something like 8 years, but there's always something new to learn.

For example today I recently learned that the tilt sensor information (the built in level you can use on the digital back) is recorded for every shot, and... you can tell C1 to access that and correct the alignment based on it, automatically.

Yes linear response is interesting and probably the real raw file, not an interpretation of it ('Film standard'), but like many, I am put off by the clear drop in saturation/color in the vital mid tones of every image, and all the hard work to restore that.  It is however a great option for sky/cloud/high tone images.
Title: Re: Using 'Linear Response' curve rather than 'Film Standard' in C1 ?
Post by: allegretto on December 08, 2013, 11:18:42 AM
How's the LuLa course?  I know and have used C1Pro for something like 8 years, but there's always something new to learn.

For example today I recently learned that the tilt sensor information (the built in level you can use on the digital back) is recorded for every shot, and... you can tell C1 to access that and correct the alignment based on it, automatically.

Yes linear response is interesting and probably the real raw file, not an interpretation of it ('Film standard'), but like many, I am put off by the clear drop in saturation/color in the vital mid tones of every image, and all the hard work to restore that.  It is however a great option for sky/cloud/high tone images.

as above, the course seems almost mandatory for such a rich and open-ended bit of software.

as far as a "drop in saturation and color" one may also consider the "curves" as a cheat of sorts and the Linear as an advantage since the curves no doubt are arbitrary in some senses and the RAW allows you to decide. Sort of like cooking from scratch vs. boxed pre-recipes.
Title: Re: Using 'Linear Response' curve rather than 'Film Standard' in C1 ?
Post by: rhadorn on December 09, 2013, 03:34:35 AM

I am glad the discussion continues, perhaps we will come to good ideas about the color compensation necessary when using the so called linear curve. At this point I would like to make my point again: the linear option in C1 does NOT deliver the raw data from the sensor.

As a first demonstration, we can read again a very good article by Bruce Fraser: http://www.adobe.com/digitalimag/pdfs/linear_gamma.pdf.
- You will see that the image corresponding to the raw data is ways darker than the image delivered by the linear curve in C1.
- If you apply to a 'linearized' image in C1 the gamma curve shown on p. 2 in the cited paper, you get a much too bright image.

Second, we can also dive into C1's blog. I recommend the reading of following article: http://blog.phaseone.com/take-full-control-of-the-tone-mapping-by-using-a-linear-film-curve/. Let me pick a few citations:

"By default the curve “Film Standard” is used. This curve is designed to give a similar tone mapping as when using transparency film. The curve has a slight S shape in order to achieve deep blacks while still maintaining details in the highlight, giving a gentle transition into overexposed areas." This shows that the Film Standard curve is not just arbitrary but... reproduces the limitations of transparency film as well as its brillance. The author adds: "The default ICC Color Profile is designed to work well together with the default curve “Film Standard”". This is the reason why I would greet the definition of a second ICC profile, which would enhance the results obtained with the linear curve.

In the fourth illustration, we see the curve which must be applied to the linear rendering to obtain the standard rendering. It is an S-shaped curve, very distinct from the gamma curve applied to true sensor data in Fraser's article.

Later on, in the discussion, Niels answers a question: "Yes, you are absolutely right. Gamma correction has been applied. "

So, the sequence seems to be the following:

RAW    gamma   LINEAR    S-shape    FILM STANDARD

In C1, linear does not refer to the linearity of the sensor data but to perceptualy equally spaced tone levels of the gamma corrected data, which nowadays cover 12-14 Ev's.

I interpret the Film Standard curve as the expression of the transition between analogue and digital photography, a time in which a good picture is still, for many people, a picture which could have been made with analogue means. In my eyes, the linear curve is as legitimate as a standard as the Film Standard in C1 and should be paired with a specific ICC profile.


Reto
Title: Re: Using 'Linear Response' curve rather than 'Film Standard' in C1 ?
Post by: allegretto on December 09, 2013, 10:14:32 AM
I'm certain that you know far more about image processing than I do. And can see what you're inferring

Here is the script from LULA's C1 course at about 3 min into Chapter 10. Basic Editing

Michael; (reference to "Linear") - "This is actually what the sensor is producing"

David; "yes"

Bruce; "Yes"

Michael; "a sensor produces a linear image...."

If I give away any more they may send a hit man

they do not address ICC profiling

cheers

h
Title: Re: Using 'Linear Response' curve rather than 'Film Standard' in C1 ?
Post by: narikin on December 09, 2013, 11:57:15 AM
I am glad the discussion continues, perhaps we will come to good ideas about the color compensation necessary when using the so called linear curve.
I interpret the Film Standard curve as the expression of the transition between analogue and digital photography, a time in which a good picture is still, for many people, a picture which could have been made with analogue means. In my eyes, the linear curve is as legitimate as a standard as the Film Standard in C1 and should be paired with a specific ICC profile.

Reto

Agree.

It seems there should be a profile for linear response for the major IQ series backs, not leaving us using one made by another route.  Have you suggested it to Phase One, or 'The Image Professor' ?  Though maybe someone very smart can explain why it might be trivial or pointless?


Title: Re: Using 'Linear Response' curve rather than 'Film Standard' in C1 ?
Post by: Vladimirovich on December 09, 2013, 01:20:54 PM
Have you suggested it to Phase One, or 'The Image Professor' ?  Though maybe someone very smart can explain why it might be trivial or pointless?

there are tehnical (software,no hardware) engineers from P1 present here (not very active though), for example this individual  = http://www.luminous-landscape.com/forum/index.php?action=profile;u=62645   or this individual = http://www.luminous-landscape.com/forum/index.php?action=profile;u=55954
Title: Re: Using 'Linear Response' curve rather than 'Film Standard' in C1 ?
Post by: tho_mas on December 09, 2013, 01:59:27 PM
in C1 you can't view an image without a tone curve nor withaout an input profile ("camera profile") applied.
All camera profiles in C1 are Gamma 1.8.
The "linear" curve produces an image with equidistant tonal values when viewed with a Gamma 1.8 profile assigned.
The term "linear curve" has nothing to do with the linearity of the sensor (or raw file).
Title: Re: Using 'Linear Response' curve rather than 'Film Standard' in C1 ?
Post by: ErikKaffehr on December 09, 2013, 02:33:44 PM
Hi,

That video lacks Jeff Schewe…

Best regards
Erik

there are tehnical (software,no hardware) engineers from P1 present here (not very active though), for example this individual  = http://www.luminous-landscape.com/forum/index.php?action=profile;u=62645   or this individual = http://www.luminous-landscape.com/forum/index.php?action=profile;u=55954
Title: Re: Using 'Linear Response' curve rather than 'Film Standard' in C1 ?
Post by: rhadorn on December 10, 2013, 01:32:10 PM

@ Narikin

Yes, I posted the question into the comments of the blog entry handling the linear curve on December 4th. I did not get any answer for now. I suppose Niels is on some trip in a warm country.

@ tho_mas

Interesting to read that C1 applies a gamma of 1.8 to the sensor data. Can you tell what is your source?

My system is calibrated for a gamma of 2.2, which is actually very common. This raises new questions:
- would the colors from the linear curve look more vivid on my system if the gamma applied by C1 was 2.2?
- is the pretty steep S-curve for the Standard rendering also a way to fill the gap between 1.8 and 2.2?
These questions may be naive, I am grateful for any expert advice.

Reto
Title: Re: Using 'Linear Response' curve rather than 'Film Standard' in C1 ?
Post by: allegretto on December 10, 2013, 02:48:42 PM
in C1 you can't view an image without a tone curve nor withaout an input profile ("camera profile") applied. This is not correct if you mean that I can't just import without designating some camera. Otherwise not sure what you mean
All camera profiles in C1 are Gamma 1.8. source?
The "linear" curve produces an image with equidistant tonal values when viewed with a Gamma 1.8 profile assigned  Again, not what the tutorial says, can you provide a source for this statement?
The term "linear curve" has nothing to do with the linearity of the sensor (or raw file). So you say...

[/quote

I don't know much... but I do know what I am told, and what I can manifestly demonstrate. It gets silly sometimes when folks seem to just want to say "you're wrong". Either you have a source for what you say or you do not. I may not be correct, it's happened before far too often, but at least I have a reasonable source that must also be wrong too. Could you provide yours?
Title: Re: Using 'Linear Response' curve rather than 'Film Standard' in C1 ?
Post by: tho_mas on December 10, 2013, 08:26:06 PM
@ tho_mas

Interesting to read that C1 applies a gamma of 1.8 to the sensor data. Can you tell what is your source?
you can inspect the input profiles with dedicated software. As a practical test you can also create a new blank image in Photoshop and assign any Capture One camera profile (for instance the "no color correction" or any other input profile of your choice) to it. Now create a black to white gradient and afterwards assign for instance ProPhotoRGB (which is Gamma 1.8 ) to the file. You'll see that the distribution of tonal values does not change after assigning ProPhoto... which shows that the original file is also Gamma 1.8.

I assume herewith I also address "allegretto's" questions...
Title: Re: Using 'Linear Response' curve rather than 'Film Standard' in C1 ?
Post by: allegretto on December 10, 2013, 09:16:20 PM
so, one should infer that the source is you?

If so, maybe you're correct and Michael and David are not. Not choosing sides, simply asking for a source. Which you have provided, correct?

Thank you. That was easy.
Title: Re: Using 'Linear Response' curve rather than 'Film Standard' in C1 ?
Post by: SecondFocus on December 10, 2013, 11:06:06 PM
Interesting discussion, much of it way technically past me. However I was just having a difficult time with one series from a shoot with someone wearing a red shirt. In this series the red reproduced in C1, Adobe and Canon DPP was not very close to the actual color by a long way. These were shot on Canon. I changed to Linear in C1 and was able to very closely match the exact color with a few slight adjustments. (White balance was not the issue). I don't have any idea as to the how and why behind it, but it is a new tool in my toolbox!

Maybe Capture One could do a new webinar on more unusual features like this. As well as addressing such problems we face.
Title: Re: Using 'Linear Response' curve rather than 'Film Standard' in C1 ?
Post by: allegretto on December 10, 2013, 11:47:27 PM
Interesting discussion, much of it way technically past me. However I was just having a difficult time with one series from a shoot with someone wearing a red shirt. In this series the red reproduced in C1, Adobe and Canon DPP was not very close to the actual color by a long way. These were shot on Canon. I changed to Linear in C1 and was able to very closely match the exact color with a few slight adjustments. (White balance was not the issue). I don't have any idea as to the how and why behind it, but it is a new tool in my toolbox!

Maybe Capture One could do a new webinar on more unusual features like this. As well as addressing such problems we face.

There is to some extent! A webinar that tells you perhaps not everything, but gives you a comprehensive overview and makes suggestions about how features might be used (as you have noticed). It's called the LULA course. It isn't free, $60. but if you're going to try to really use the program it's a bargain.

Now as noted above, maybe they are not correct about the fine technical stuff (sooner or later David or Michael will probably help us here) but they sure have great ideas on rescue. Raber goes into a lot of this kind of stuff and how you can fine tune specific tonal metrics.

Good stuff...
Title: Re: Using 'Linear Response' curve rather than 'Film Standard' in C1 ?
Post by: tho_mas on December 11, 2013, 05:47:11 AM
so, one should infer that the source is you?
the source are the actual input profiles available in Capture One (all of them).
Title: Re: Using 'Linear Response' curve rather than 'Film Standard' in C1 ?
Post by: Doug Peterson on December 11, 2013, 06:04:15 PM
Maybe Capture One could do a new webinar on more unusual features like this. As well as addressing such problems we face.

We address a variety of such niche tools and workflows in our Capture One Masters Program (https://digitaltransitions.com/event/training).
Title: Re: Using 'Linear Response' curve rather than 'Film Standard' in C1 ?
Post by: rhadorn on December 12, 2013, 08:53:54 AM
We address a variety of such niche tools and workflows in our Capture One Masters Program (https://digitaltransitions.com/event/training).


Hi Doug,

Nice to read somebody having a deep knowledge of Capture One here. And thank you for the hint, that we may find an answer to our questions in your tutorials.

Perhaps you would be more successfull in selling them to the folks here if you gave us a demonstration of your capacity to answer the question asked about the icc profile, which would serve le linear curve as well as the default icc curve serves the standard curve. I asked that same question in Niel's blog and am still waiting for an answer, so I start considering that there is perhaps no answer at all on the side of Phase One.

By the way, the e-mail address on the page you refer to is false, it probable should be dep@digitaltransitions.com and not dep@digitransitions.com.

...

Welcome


Reto
Title: Re: Using 'Linear Response' curve rather than 'Film Standard' in C1 ?
Post by: Doug Peterson on December 12, 2013, 09:54:52 AM
Nice to read somebody having a deep knowledge of Capture One here. And thank you for the hint, that we may find an answer to our questions in your tutorials.

Perhaps you would be more successfull in selling them to the folks here if you gave us a demonstration of your capacity to answer the question asked about the icc profile, which would serve le linear curve as well as the default icc curve serves the standard curve. I asked that same question in Niel's blog and am still waiting for an answer.

Thanks, though the need for "demonstration" in somewhat questionable as we've never had a COMP class that wasn't sold out. I'm guessing from the fact that you have 5 posts here than you're new - so you've no doubt missed the literally hundreds of times I've answered tricky questions about Capture One (and Phase/Leaf/Hassy hardware) here and on other forums.

In this case I'd have to defer the complex, use-specific (even if you think it is not), and niche discussion of proper pairing of [ICC profile] and [camera curve] with any given [use case] to our more in-depth classes.

Someone had commented that there should be more webinars/classes for these sorts of advanced topics, so my link seemed relevant.

Thanks for the note about the website - I'll have our web person correct that.
Title: Re: Using 'Linear Response' curve rather than 'Film Standard' in C1 ?
Post by: torger on December 13, 2013, 08:14:13 AM
With a recent version of Capture One you can output TIFF files with embedded camera ICC profile and also get the TIFFTAG_TRANSFERFUNCTION set. If you reverse that transfer function you should get back to linear camera data, pre-processed with white balance but otherwise in native camera color space. If it's a Leaf ICC profile it has also been preprocessed from camera RGB to Prophoto RGB though, using the CaptProf_color_matrix embedded in the raw file.

Note that a "linear" curve will not look linear, as it must also take into account the ICC gamma, which generally is 1.8. For an Aptus-II the resulting transfer function from a linear curve is almost exactly an x^1.8 function, ie effectively linear as the embedded ICC profile has gamma 1.8. For many other cameras (almost all?) there's deviation though, typically the transfer function leaves some space in the highlights. This might be due to give the ICC cLUTs proper headroom or to hide a noisy clip level which some cameras have.

My current understanding is that the bundled ICCs are generally designed for the "standard curve" or curves similar to it - probably all curves *except* the linear curve is "similar enough" to the standard curve. A linear curve is however far from this standard curve and therefore may cause the LUT conversions become a bit distorted, and thus it would not be recommended to use the bundled ICCs when linear curve. I've tried to find some "official" statement regarding this but not received any though. I guess they want you to take a course ;)

I have not tested that many images but with a Leaf back and a Canon 5D mark 2 one can see that (white) skin get a slight greenish cast if the ICC is applied to a linear curve while it looks good with the standard curve. Depending on subject it may be difficult to decide which one is better, but if you layer the two images on top and switch fast between them one can clearly see that the color does change despite that you're using the same ICC profile, and with this fact I think it's reasonable to assume that the bundled ICC profiles have been designed to look good with the standard curve.
Title: Re: Using 'Linear Response' curve rather than 'Film Standard' in C1 ?
Post by: Vladimirovich on December 13, 2013, 09:59:46 AM

Note that a "linear" curve will not look linear, as it must also take into account the ICC gamma, which generally is 1.8.

extract profile, replace gamma with gamma1, replace profile...
Title: Re: Using 'Linear Response' curve rather than 'Film Standard' in C1 ?
Post by: torger on December 13, 2013, 10:42:52 AM
extract profile, replace gamma with gamma1, replace profile...

An interesting experiment, not sure what it would yield though. Do you mean that the modified profile would render colors correctly with the linear curve applied?

Most of the bundled profiles actually don't have a 1.8 gamma curve in the TRC tags, it's rather a 256 point curve with a shape which is similar (but still quite different from) a 1/1.8 gamma curve, but the effective gamma with the A2B0 LUT active becomes 1.8. I'm new to LUTs and have not figured out all details with them, but I know as much that you can do lots of tricks in the LUT, I assume this includes changing gamma.
Title: Re: Using 'Linear Response' curve rather than 'Film Standard' in C1 ?
Post by: tho_mas on December 13, 2013, 01:58:34 PM
extract profile, replace gamma with gamma1, replace profile...
how do you do this? with what software? I wonder whether it's possible to change the Gamma of table based profiles just like in matrix profiles? In my opinion it's only possible with matrix profiles (essentially defined by primaries and TRC and WP)... and if you change the Gamma of an LUT profile you'll screw the entire profile (the way it models colour that is).

side note regarding my posts above: reading the other thread on this forum regarding Leaf profiles... I've looked into the Leaf profiles and these do infact contain different TRCs. All other input profiles (at least those I've ever inspected) effectively assign Gamma 1.8 ...
Title: Re: Using 'Linear Response' curve rather than 'Film Standard' in C1 ?
Post by: Vladimirovich on December 13, 2013, 02:40:31 PM
how do you do this? with what software? I wonder whether it's possible to change the Gamma of table based profiles just like in matrix profiles? In my opinion it's only possible with matrix profiles (essentially defined by primaries and TRC and WP)... and if you change the Gamma of an LUT profile you'll screw the entire profile (the way it models colour that is).

I assumed that poster was interested just in tiff w/ linear data in it w/o embedded ICC profiles messing w/ that, so get rid of LUTs then... no ? because naturally the whole point of non-matrix profiles is to make quite non linear color transforms

Title: Re: Using 'Linear Response' curve rather than 'Film Standard' in C1 ?
Post by: tho_mas on December 13, 2013, 02:56:30 PM
I assumed that poster was interested just in tiff w/ linear data in it w/o embedded ICC profiles messing w/ that, so get rid of LUTs then... no ? because naturally the whole point of non-matrix profiles is to make quite non linear color transforms
but the input profiles (camera profiles) in Capture One are desgined differently. The non-linearity of the RAW capture of any camera is linearized "under the hood".

The "camera profiles" (selectable in "Base Characteristics") are designed ... if you want so ... as camera-specific "working spaces" providing a neutral grey axis (producing a distirbution of luminance levels that is exactly Gamma 1.8 ... except for Leaf backs). This is why you can embed the camera profiles on export/processing and work the files with the "camera profile" embedded in Photoshop just like with any other working space. (Except, of course, with an input profile only containing an "A2B0" table you can't create composites ... at least you have to establish workarounds if want to do so).

What you infact can do... if you want to ...
- create a profile for instance with ProPhoto primaries and WP but with Gamma 1.0 (you can create a rudimentary version of it also in Photoshop)
- edit your captures in C1 with the generic or dedicated input profile and the linear curve applied and select your self baked Gamma 1.0 profile as target when processing

not sure that you will gain anything ... but at least this would be doable :-)

Title: Re: Using 'Linear Response' curve rather than 'Film Standard' in C1 ?
Post by: AreBee on December 19, 2013, 09:15:47 AM
Allegretto,

Quote from: allegretto
...the "linear" is the actual RAW file curve. The Others, "film standard" are curved renditions of the RAW

This makes sense to me - I currently am trialling C1 and noticed that one NEF file in particular very obviously is wrong when the default film curve is adopted, whereas the same file looks correct when the linear curve is adopted, and similar to how it is rendered in Nikon Capture NX2. Having said that, the file in question appears to be the odd one out of those that I have examined, as every other NEF looks reasonable with the film curve applied.
Title: Re: Using 'Linear Response' curve rather than 'Film Standard' in C1 ?
Post by: allegretto on December 19, 2013, 10:18:57 AM
Allegretto,

This makes sense to me - I currently am trialling C1 and noticed that one NEF file in particular very obviously is wrong when the default film curve is adopted, whereas the same file looks correct when the linear curve is adopted, and similar to how it is rendered in Nikon Capture NX2. Having said that, the file in question appears to be the odd one out of those that I have examined, as every other NEF looks reasonable with the film curve applied.

I suppose "Standard Film" has it's matches and mis-matches too. That's what all those sliders and histograms are about

As far as "linear" goes... don't tell anyone that or you will be WRONG, WRONG WRONG,,, I guess...
Title: Re: Using 'Linear Response' curve rather than 'Film Standard' in C1 ?
Post by: ErikKaffehr on December 30, 2013, 05:56:01 PM
Hi,

I tried some images using both linear and film curves. The "film curves" make your image to bright, so exposure needs to be reduced 1-1.5 stops. The linear curve looks right, but I feel colours are better with the "film curve".

It seems that colour handling is optimised for film curve.

Best regards
Erik


I suppose "Standard Film" has it's matches and mis-matches too. That's what all those sliders and histograms are about

As far as "linear" goes... don't tell anyone that or you will be WRONG, WRONG WRONG,,, I guess...
Title: Re: Using 'Linear Response' curve rather than 'Film Standard' in C1 ?
Post by: tho_mas on December 31, 2013, 11:01:41 AM
The "film curves" make your image to bright, so exposure needs to be reduced 1-1.5 stops.
The Standard Film Curve is supposed to be used with a conventional lighting meter... AFAIK. I've once tested exposure on a Kodak Q14 chart. I've measured the actual light (not the reflecting light) with a hand meter and set the camera/lens accordingly. My P45 matched the respective RGB values of the 18% grey patch very, very good with the Standard Film Curve applied.
Now, when you expose too much to the right, the Standard film curve will blow differentiation in bright tonal values. When the motif fits into the dynamic range of the camera and you like the look of the Standard film curve (I do... actually) then you can expose for mid grey. When the motif exceeds the dynamic range of the camera it's certainly more appropriate to expose to the highlights and use either the "Extra Shadow" film curve (and recover some highlights) or the linear curve.
Title: Re: Using 'Linear Response' curve rather than 'Film Standard' in C1 ?
Post by: ErikKaffehr on December 31, 2013, 12:01:10 PM
Hi,

The reason for ETTR is that we want minimise noise, or to be more exact, maximise signal/noise ratio. Exposing for highlights is essential to utilise the sensor maximally. It works of course only at base ISO. The whole idea is to maximise exposure. What I do is that I use RawDigger to check the the raw files for exposure. It is of course something I do in post, it is a learning experience.

The enclosed figure is a good example. Exposure was limited by the white wall on the castle, this was judged by histogram and blinking highlights.

I enclose the raw histogram and default rendering in C1 (using WB from a grey card shot in another frame) and my own processing in LR 5.3, the C1 looks good, in my eyes.

Best regards
Erik

The Standard Film Curve is supposed to be used with a conventional lighting meter... AFAIK. I've once tested exposure on a Kodak Q14 chart. I've measured the actual light (not the reflecting light) with a hand meter and set the camera/lens accordingly. My P45 matched the respective RGB values of the 18% grey patch very, very good with the Standard Film Curve applied.
Now, when you expose too much to the right, the Standard film curve will blow differentiation in bright tonal values. When the motif fits into the dynamic range of the camera and you like the look of the Standard film curve (I do... actually) then you can expose for mid grey. When the motif exceeds the dynamic range of the camera it's certainly more appropriate to expose to the highlights and use either the "Extra Shadow" film curve (and recover some highlights) or the linear curve.
Title: Re: Using 'Linear Response' curve rather than 'Film Standard' in C1 ?
Post by: BartvanderWolf on December 31, 2013, 12:43:34 PM
The Standard Film Curve is supposed to be used with a conventional lighting meter... AFAIK. I've once tested exposure on a Kodak Q14 chart. I've measured the actual light (not the reflecting light) with a hand meter and set the camera/lens accordingly. My P45 matched the respective RGB values of the 18% grey patch very, very good with the Standard Film Curve applied.

Hi,

That's because it underexposes the Raw exposure relative to it's ISO setting. The subsequent highlight clipping by using a Film response curve then corrects for that underexposure, or it clips highlights if scene contrast is high and incident light metering was used uncorrected.

Quote
Now, when you expose too much to the right, the Standard film curve will blow differentiation in bright tonal values. When the motif fits into the dynamic range of the camera and you like the look of the Standard film curve (I do... actually) then you can expose for mid grey. When the motif exceeds the dynamic range of the camera it's certainly more appropriate to expose to the highlights and use either the "Extra Shadow" film curve (and recover some highlights) or the linear curve.

The linear response curve also improves highlight contrast. Certain subject matter benefits a lot from that, e.g. white clouds in a sunny scene.

Cheers,
Bart
Title: Re: Using 'Linear Response' curve rather than 'Film Standard' in C1 ?
Post by: tho_mas on December 31, 2013, 05:48:34 PM
we want minimise noise, or to be more exact, maximise signal/noise ratio.
No. What we (photographers, imaging people, designers … whatever) want is a nice, sexy image. When the lighting of the scene fits into the dynamic range of the camera (sensor) why on earth would I "overexpose" (overexpose in the sense of ETTR when it's not needed). Just to fiddle around in software and to dial down the brightness afterwards? Ridiculous!

That's because it underexposes the Raw exposure relative to it's ISO setting. The subsequent highlight clipping by using a Film response curve then corrects for that underexposure, or it clips highlights if scene contrast is high and incident light metering was used uncorrected.

The linear response curve also improves highlight contrast. Certain subject matter benefits a lot from that, e.g. white clouds in a sunny scene.
Bart, I know all that. I do use the linear curve as well. But I use it when needed and not as the starting point of all my editing.
The non-plus P-backs show the histogram with the linear curve applied on the LCD (unlike the P plus backs that show the histo with the Standard Film Curve applied on the LCD). I use both a non plus and a plus back and know how to expose with both of them to get a decent image. But, again, when I do not clip the blacks nor the highlights in a certain scene … then I expose for a "nice" image rather than for highlights. Why would I?
Title: Re: Using 'Linear Response' curve rather than 'Film Standard' in C1 ?
Post by: ErikKaffehr on January 02, 2014, 12:31:11 PM
Hi,

I guess I need to retract a bit on the necessity on ETTR, I tried to demonstrate the effect by example. What I have seen is that the improvements I expected from ETTR were visible in histograms but not really visible in photographs. That said, I still feel that maximising exposure is a good idea.

What I also see is that histogram and blinking highlights on my P45+ are pretty good indication on where exposure will end up.

Best regards
Erik


No. What we (photographers, imaging people, designers … whatever) want is a nice, sexy image. When the lighting of the scene fits into the dynamic range of the camera (sensor) why on earth would I "overexpose" (overexpose in the sense of ETTR when it's not needed). Just to fiddle around in software and to dial down the brightness afterwards? Ridiculous!
Bart, I know all that. I do use the linear curve as well. But I use it when needed and not as the starting point of all my editing.
The non-plus P-backs show the histogram with the linear curve applied on the LCD (unlike the P plus backs that show the histo with the Standard Film Curve applied on the LCD). I use both a non plus and a plus back and know how to expose with both of them to get a decent image. But, again, when I do not clip the blacks nor the highlights in a certain scene … then I expose for a "nice" image rather than for highlights. Why would I?
Title: Re: Using 'Linear Response' curve rather than 'Film Standard' in C1 ?
Post by: tho_mas on January 02, 2014, 05:46:15 PM
That said, I still feel that maximising exposure is a good idea.
Me too as long as we talk about increased exposure to get the shadows of a high dynamic range scene into the histogram (without clipping highlights of course). But when the dynamic range of the scene can be fully captured by the camera there is no need to push exposure, IMO.
In my experience you can beat a file of a Phase back excessively in post without introducing unwanted noise or any other artefacts (tonal banding... whatever) ... provided that the capture didn't clip shadows or highlights initially. This goes even for my old P45 (non plus ... from 2005).
Title: Re: Using 'Linear Response' curve rather than 'Film Standard' in C1 ?
Post by: Vladimirovich on January 02, 2014, 06:25:15 PM
provided that the capture didn't clip shadows
and what does it mean exactly - clipping shadows in raw channels ?
Title: Re: Using 'Linear Response' curve rather than 'Film Standard' in C1 ?
Post by: tho_mas on January 02, 2014, 06:34:44 PM
and what does it mean exactly - clipping shadows in raw channels ?
yes
Title: Re: Using 'Linear Response' curve rather than 'Film Standard' in C1 ?
Post by: Vladimirovich on January 03, 2014, 10:49:02 AM
yes
I was asking what do you mean by clipping shadows when you are talking about raw ? is it somewhat related to the high readout noise of consumer level MF cameras v CCD sensors vs consumer level cameras w/ CMOS sensors ?
Title: Re: Using 'Linear Response' curve rather than 'Film Standard' in C1 ?
Post by: ErikKaffehr on January 04, 2014, 09:33:29 PM
Hi,

What I see is that the shadows don't clip on my P45+ but go into a continuum of noise. On my Alpha 900 I have seen some clipping of dark tones.

I see two reasons to maximise exposure, one is to keep down shot noise in light and midtone areas. I tried to demonstrate this and it is easy to show the issue mathematically but signal noise ratio is so good that the effect is not obvious in practice. I can measure it but I cannot see it.

The other reason is to protect shadow detail. Higher exposure gives less shot noise in the darks.

In general I would say that noise in dark areas is an area where the P45+ doesn't impress. It is also a reason that they don't really impress at higher ISOs.

Chris Barrett published some raw images from Sony Alpha 7r and IQ260 (?), which he exposed at 100 ISO. Those IQ260 images were noisy in both dark midtones and in the darks, while the Sony image was smooth. Both IQ260 and Sony Alpha have a base ISO of 50 (nominally).

What I have seen on my P45+ is that shadows are more problematic than on the Alpha 99, so I feel a greater need for exposing high on the P45+ than on the Alpha.

Best regards
Erik

I was asking what do you mean by clipping shadows when you are talking about raw ? is it somewhat related to the high readout noise of consumer level MF cameras v CCD sensors vs consumer level cameras w/ CMOS sensors ?