AWB vs UniWB experiment

Started Aug 8, 2012 | Discussions
Chris Noble
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AWB vs UniWB experiment
Aug 8, 2012

If these acronyms mean nothing to you or leave you indifferent, this thread is not for you!

I'd like to propose an AWB vs. UniWB experiment. We will all post comparisons of AWB and UniWB shots of the same scene, same time, shooting Raw and ETTR.

This is a controversial topic and we all need more data.

Comments? Let's get the conditions agreed to exactly first.

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dcassat
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Parameters need to be set for testing
In reply to Chris Noble, Aug 8, 2012

I'm certainly willing to join in, I'll probably learn something from it

Perhaps we could agree on a rough set of parameters, setting, time of day, low/high DR, or just an indoor test shot under a incandescent lamp, etc?

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Dan

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Vlad S
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Some suggestions
In reply to dcassat, Aug 8, 2012

dcassat wrote:

Perhaps we could agree on a rough set of parameters, setting, time of day, low/high DR, or just an indoor test shot under a incandescent lamp, etc?

I don't think there is a need to set parameters. Different users have different priorities, and I think it would be beneficial to cover more shooting styles and scenes, rather than fewer. I only suggest that in the subject line we write how much of advantage that specific example shows, so that it would be easy to summarize the results in the end. In addition it could be useful to also list in the subject line the camera model, and possibly the lighting conditions, but keep it short enough so that it's not truncated when posted.

I also think it could be useful to provide the RAW files. May be create a special dropbox for those? The reason is that I find that although the RAW histogram often shows no data at the right side, the colors still look blown in the full color image - possibly because they fall out of gamut. I see this most often on the flower petals in full sun, especially pink ones. It is possible that someone may be able to extract better results.

Vlad

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Chris Noble
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Re: Parameters need to be set for testing
In reply to Vlad S, Aug 8, 2012

My thoughts:

1) Wide range of subjects and lighting situations (that is part of the controversy).
2) Shoot one UniWB, one AWB, both ETTR with similar blinkies.

3) Post both with comments on what you saw in PP. Posting both Raw histograms as well gets you additional bragging rights.

4) Be fair and post all your examples (don't cherry-pick conditions that favor your own brand of white-balance "religion."

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Chris Noble
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One more rule of the competition and thread
In reply to Chris Noble, Aug 8, 2012

5) No sarcastic, demeaning or side-topic comments. Just the facts, analysis and respectful questions.

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Detail Man
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Re: Parameters need to be set for testing
In reply to Chris Noble, Aug 8, 2012

Chris Noble wrote:

My thoughts:

1) Wide range of subjects and lighting situations (that is part of the controversy).
2) Shoot one UniWB, one AWB, both ETTR with similar blinkies.

3) Post both with comments on what you saw in PP. Posting both Raw histograms as well gets you additional bragging rights.

4) Be fair and post all your examples (don't cherry-pick conditions that favor your own brand of white-balance "religion."

Just a peep from me. Seems like the dominant interest may well be the E-M5 preview/review "blinkies". On that subject, it appears (form gollywop 's excellent investigations) the "blinkies" are complicated, different in characteristics for preview and review, and preview frame-rate, and (this is important), rather than being an (estimation) of absolute levels of image-data levels, there seems to be evidence that indicates that their characteristics and functionality are variable - depending on the contrast-ratio (sometimes called the "DR") of the scence being previewed and metered upon.

Note that if the blinkies function more like a "peak/average ratio", or some kind of "contrast-ratio" detection system (as opposed to an absolute indicator of signal-levels), then it would seem to be very, very important to set forth the specific contrast-ratios of the type of scenes to be tested ...

What seems troubling is that in the very application where "ETTR" is most useful and viable (lower/moderate, as opposed to very high "contrast-ratio" scenes), there have been indications reported ( gollywop ) that these are situations where the blinkies may become more unreliable in their measurement accuracy relative to a function of estimating peak recorded (RAW) signal-levels.

DM ...

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Chris Noble
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Re: Parameters need to be set for testing
In reply to Detail Man, Aug 8, 2012

Detail Man said:
Seems like the dominant interest may well be the E-M5 preview/review "blinkies".

I suggest any camera with UniWB and RGB review histogram and blinkies is OK. We're gathering data here. And the E-M5 fanatics are likely to discover their next "world's greatest camera" soon (I'm quite pleased with my G1).

I also suggest blinkies and histogram review as the reportable criterion, not preview. Preview blinkies is a sub-cult.

It would seem to be very, very important to set forth the specific contrast-ratios of the type of scenes to be tested ...

Let's not limit the data before we've collected it...

What seems troubling is that in the very application where "ETTR" is most useful and viable (lower/moderate, as opposed to very high "contrast-ratio" scenes), there have been indications reported (gollywop) that these are situations where the blinkies may become more unreliable in their measurement accuracy relative to a function of estimating peak recorded (RAW) signal-levels.

Good! Let's shine some blinking light on all this ;).

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Detail Man
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Re: Parameters need to be set for testing
In reply to Chris Noble, Aug 8, 2012

Chris Noble wrote:

Detail Man said:
Seems like the dominant interest may well be the E-M5 preview/review "blinkies".

I suggest any camera with UniWB and RGB review histogram and blinkies is OK. We're gathering data here. And the E-M5 fanatics are likely to discover their next "world's greatest camera" soon (I'm quite pleased with my G1).

Makes sense to be inclusive there. One hopes that if/when this or that camera's Live Histograms (or "blinkies") are compared, that the interest is in the (as much as possible, objective) reality for a user - and not degenerate into a camera-sales convention of polarized devotees and pre-warped biased outlooks. All observations and impressions are (naturally) going to exist through the "spectacles" (in general) which various camera models provide to the user. Not all news is glowing.

I also suggest blinkies and histogram review as the reportable criterion, not preview. Preview blinkies is a sub-cult.

True. In some ways, they seem like a "promise" that does not necessarily fill the role with precision

It would seem to be very, very important to set forth the specific contrast-ratios of the type of scenes to be tested ...

Let's not limit the data before we've collected it...

In relation to E-M5 (and possibly other Oly preview/review blinkies) it may important to do that ...

What seems troubling is that in the very application where "ETTR" is most useful and viable (lower/moderate, as opposed to very high "contrast-ratio" scenes), there have been indications reported (gollywop) that these are situations where the blinkies may become more unreliable in their measurement accuracy relative to a function of estimating peak recorded (RAW) signal-levels.

Good! Let's shine some blinking light on all this ;).

For those engaged in gauging RAW exposure accurately, such a process can only lead to realism

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Detail Man
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Re: Parameters need to be set for testing - Measurement Tools
In reply to Chris Noble, Aug 8, 2012

Chris Noble wrote:

I also suggest blinkies and histogram review as the reportable criterion, not preview. Preview blinkies is a sub-cult.

I think that such makes sense. In order to verify what the cameras themselves indicate, the use of RawDigger is an accurate standard that RAW processors (particularly commercial ones) are a poor (and often misleading) substitute for. RawDigger is free, stable, and non-invasive. For Win/Mac:

http://www.rawdigger.com/news/rawdigger-0-9-11

This thread includes some helpful information for using RawDigger , and interpreting output-data:

http://forums.dpreview.com/forums/readflat.asp?forum=1041&message=41462987

To cut through a fair amount of "random noise", see my conversations with dcassat in the thread.

RawDigger is fully capable of accurately measuring the important E-M5 ORF RAW image-file data.

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Vlad S
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Please share RAW files
In reply to Chris Noble, Aug 8, 2012

I have set up a dropbox account for this experiment. If you want to share RAW files and do not have a place where you can upload them for sharing, you are welcome to send me a PM and I will give you a password to upload the files.

Vlad

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Chris Noble
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Re: Please share RAW files
In reply to Vlad S, Aug 8, 2012

Great, I will repost a full set of experiment parameters when all the suggestions are in and include your Dropbox option for the Raw files.

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dcassat
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A few things
In reply to Chris Noble, Aug 8, 2012

You probably have all of this in your head already but some folks that have not done controlled testing for troubleshooting purposes may not know.

I would recommend that this be done from a tripod with no lens changes or other changes beside WB.

I happen to belong the the sub-cult and usually do my ETTR with preview blinkies as it's only recently that their consistency has come into serious question. Some clarity with regard to the post shot exposure adjustment would be helpful. As in "no blinkies in the post shot exposure" or "one click back from the post shot blinkies" or a "properly right aligned histogram before a overexposure warning is seen"

Perhaps we can actually have some valuable information when we're finished!

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Franka T.L.
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you better teach the wider audience how to do UniWB first .. n/t
In reply to Chris Noble, Aug 8, 2012
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Detail Man
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Re: you better teach the wider audience how to do UniWB first
In reply to Franka T.L., Aug 8, 2012

Two already existing forum references:

EM5: http://forums.dpreview.com/forums/read.asp?forum=1041&message=41245342

GH2: http://forums.dpreview.com/forums/readflat.asp?forum=1041&message=40469300

To easily determine the Red and Blue color-coeffients for recorded image-file meta-data (when configuring for UniWB), as well as to accurately determine recorded RAW image-file ADU levels (when comparing camera playback histograms and/or blinkies to a reliable measurement instrument), download and install the free, stable, and non-invasive RawDigger (for Win 32/44, and for Mac 32/64) here:

http://www.rawdigger.com/news/rawdigger-0-9-11

Leave the default preferences in RawDigger intact (to ensure automatic black-level subtraction). Use the " Exif " button to access the color-coefficients from the included ExifTool meta-data tool.

Other free apps. exist that can read the same color coefficients from recorded JPG "Maker Notes".

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Chris Noble
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Re: A few things
In reply to dcassat, Aug 8, 2012

dcassat said:

I happen to belong the the sub-cult and usually do my ETTR with preview blinkies as it's only recently that their consistency has come into serious question. Some clarity with regard to the post shot exposure adjustment would be helpful. As in "no blinkies in the post shot exposure" or "one click back from the post shot blinkies" or a "properly right aligned histogram before a overexposure warning is seen".

Yes; that comment is useful from those who submit. How about if we suggest that whatever blinkie or histogram condition they choose for one of the WB settings (Uni or A), they apply the same conditions to the other, and tell us what they did ("x" eV down from blinkies, only specular highlights, etc).

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Chris Noble
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No teaching, no convincing, except by the results
In reply to Franka T.L., Aug 9, 2012

In order for this experiment to be useful, we need to focus on data collection. We can't try to educate and convince as well. Apprentices will have to research other sources and links, and doubters can spend their time arguing in other threads about other topics. Otherwise this will become just another argument hole. The path to blinkie-free Raw enlightenment is not for the faint of heart.

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Detail Man
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Re: A few things
In reply to Chris Noble, Aug 9, 2012

Chris Noble wrote:

... only specular highlights ...

I would suggest that if highlights exceeding a camera-determined threshold are allowed, then the data would descend in vagaries. "Specular highlights" could mean just about anything to anybody ?

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Chris Noble
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Specular highlights not allowed...
In reply to Detail Man, Aug 9, 2012

Detail Man said:

I would suggest that if highlights exceeding a camera-determined threshold are allowed, then the data would descend in vagaries. "Specular highlights" could mean just about anything to anybody ?

Dealing correctly with specular highlights is one sign of a skillful TTRE (to-the-right-exposer). But I agree with you. For this experiment, we should require that no part of the image be saturated.

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rkeller
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Re: A few things
In reply to Detail Man, Aug 9, 2012

I think "specular highlights" have a pretty standardized definition. http://en.wikipedia.org/wiki/Specular_highlight

One could even get lost in the equations if one so chose:

"In the Phong reflection model, the intensity of the specular highlight is calculated as:

Where R is the mirror reflection of the light vector off the surface, and V is the viewpoint vector."

Detail Man wrote:

Chris Noble wrote:

... only specular highlights ...

I would suggest that if highlights exceeding a camera-determined threshold are allowed, then the data would descend in vagaries. "Specular highlights" could mean just about anything to anybody ?

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rrr_hhh
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Re: Specular highlights not allowed...
In reply to Chris Noble, Aug 9, 2012

Chris Noble wrote:

Detail Man said:

I would suggest that if highlights exceeding a camera-determined threshold are allowed, then the data would descend in vagaries. "Specular highlights" could mean just about anything to anybody ?

Dealing correctly with specular highlights is one sign of a skillful TTRE (to-the-right-exposer). But I agree with you. For this experiment, we should require that no part of the image be saturated.

I think that including such a rule will introduce a bias in the test : those who use ETTR without UniWB knows by experience how much of the blinkies they can accept before blowing highlights, while those advocating for the exactness of UniWB also know that you are nearer of blowing highlights, so imposing the use of the same level of blinkies for both isn't fair. It won't correspond to the way those photographers are working usually.

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