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Re: White balance in RAW - necessary ?
Old 06-18-2007, 11:43 AM   #11 (permalink)
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Quote:
Originally Posted by rolandogomez View Post
See my long post above, basically from two professors with extensive background in digital imaging and RAW.
Nope, been proven, see books by Mikkel Aaland, specifically "Shooting Digital," pages 255-264.
You can find all sorts of people across the Internet that disagree with the statements you quote in your original post from the above book.

I have run my own tests on this with the Canon 20D. What I found was that if I shot the same shot twice (on a tripod, controlled lighting conditions, one shot with AWB set and the other set to K5000) and then took the two resulting RAW files and extracted just the RAW data (discarding the m e t a data and the embedded JPG), that the data was essentially identical.

I don't know where the Aaland data is coming from as he doesn't seem to quote his sources in way that one can independently verify them. This is a very controversial issue and there are many arguments pro and con floating around in print on one side or the other.

But bottom line, we both agree that it is critical to set WB at the time of shooting and not later, so that is what really matters.


On another note, it is true that the RAW images will be different from different cameras. That is due to the difference in the algorithms that each use to convert the data from the sensors to the internal memory buffer. But for each camera, it will be consistent for that camera. Also each camera is an individual unit. So Canon 20D 1 will not gives the same RAW data as Canon 20D 2. They use the same algorithm, but at any given time you can't guarantee that all of the pixel capturing points are actually working (its a statistical thing - and governed somewhat by the uncertainty principle). Also dust on the sensor will be different between cameras and that effects the RAW data, etc.

Cheers,
rfs
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Re: White balance in RAW - necessary ?
Old 06-18-2007, 01:07 PM   #12 (permalink)
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You missed point, the point is how the RAW data is interpreted in the camera processing, before it's even written to the camera buffer or digital capture card. Of course the metadata will be identical, what is metadata? Sometimes only a text file of data about data itself, how the image was captured--metadata does nothing to "interpret" the image during capture. The chapter in Aaland's book describes their methods, mainly by Mr. Holm, how they came about this summation. The book also has photos showing what image data looks like after it comes off the sensor, before it goes through post-capture camera processing.

They also used a process that illustrates how "data is discarded" (in RAW) when white balance is determined and applied--before you even download the file for your own conversion and post-production.

He also states, "I've also stated that saving RAW data doesn't automatically translate into getting the best quality image. IN fact, if you don't process RAW properly, you'll end up with an image that is inferior to what a camera can do if left to use its own onboard processors."

The bottom line, white-balance in the camera correctly during the shooting will be more accurate then if applied later in post-production. Wishing you the best, rg sends!
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Re: White balance in RAW - necessary ?
Old 06-18-2007, 02:06 PM   #13 (permalink)
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Quote:
Originally Posted by rolandogomez View Post

The bottom line, white-balance in the camera correctly during the shooting will be more accurate then if applied later in post-production. Wishing you the best, rg sends!
The bottom line is what counts.
No matter whether agreement is reached on what is happening as the data is translated from the millions of photosites to the data that reaches the internal buffer, it is still essential that we set proper white balance at the time we're shooting and not after.
The other factor that goes without stating is that it is important to "nail" the exposure since that "will" effect the RAW data significantly.

Cheers,
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Re: White balance in RAW - necessary ?
Old 06-18-2007, 04:40 PM   #14 (permalink)
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Thank you..

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Great thinking Jayson, wishing you the best, rg sends!
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Re: White balance in RAW - necessary ?
Old 06-18-2007, 04:45 PM   #15 (permalink)
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So these were shot one after the other, or RAW+JPG? Big difference with RAW+JPG as the JPG is not the highest possible JPG. Also, this will vary from camera to camera, model to model. I'm talking about shooting a RAW image correctly (exposure and white balance), then shooting one in JPG (highest quality) without changing anything...thanks, rg.
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RAW+JPG and discussion ...
Old 06-18-2007, 05:08 PM   #16 (permalink)
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Originally Posted by rolandogomez View Post
So these were shot one after the other, or RAW+JPG? Big difference with RAW+JPG as the JPG is not the highest possible JPG. Also, this will vary from camera to camera, model to model. I'm talking about shooting a RAW image correctly (exposure and white balance), then shooting one in JPG (highest quality) without changing anything...thanks, rg.
These were shot on a Canon 20D in RAW + JPG. On the 20D, it does use the highest possible JPG quality and size (see page 46 of the 20D manual). It will vary from camera to camera, however, since each camera brand processes the photosites using their own special interpretation software. But you can see another comparison on page 35 of "Shooting Digital" by Aalands (2nd edition). The problem with shooting two images, is that they are never really exactly the same because of quantum fluctuation and the uncertainty principle and the model never gets exactly the same pose. With RAW + JPG you are allowing the camera to produce both images from the same exact set of data.

You can test the two image approach pretty simply. Put a camera on a tripod and take a properly exposed shot of a still life using studio lighting. Shoot in RAW and shoot the image twice. Now run a byte by byte comparison on the two RAW files and you'll find that they vary in the RAW data portion of the files (naturally they'll have some variance in other areas such as the **** data area). So we're comparing the RAW data section of the two files but not the **** data area or the embedded JPG preview.

By the way, when you shoot RAW with Canon dSLRs and use the RAW + JPG mode, you actually end up with three JPG files. One is embedded in the RAW file (the preview image used by LCD) and the other is a thumbnail embedded in the JPG file.

NOTE: IN the above I typed the word "m e t a" without the spaces. For some reason G1 keeps filtering the word m e t a and it should not in my view.

cheers,
rfs
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Last edited by R_Fredrick_Smith; 06-18-2007 at 05:10 PM.. Reason: correct speeling, at m e t a note
 
Re: White balance in RAW - necessary ?
Old 06-20-2007, 01:28 AM   #17 (permalink)
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Interesting conversation, I agree from the workflow standpoint that getting your CWB Before the shoot. As to the Raw really being lossless dunno really, although I found it a "learning experience" reading your posts thank you R_Frederick_Smith and rolandogomez.
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Re: White balance in RAW - necessary ?
Old 06-20-2007, 04:23 PM   #18 (permalink)
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Rolando talked about data being interpolated in the RAW file. I can't comment on formats other than Canon, but I understood the RAW data in a CR2 file to be the sensor data, that is, the pre-interpolation data, aka the Bayer matrix data - and the file sizes suggest that this is the case. I also understood the white balance information in the RAW file to be nothing more than a piece of metadata.

I'd be very interested to see a series of RAW files shot of the same scene at different white balances (I might even try this myself) - same camera, same lights, same scene, just different white balance settings. I would expect the RAW data to be essentially the same (minor variance has to be expected due to noise, if nothing else). This is quite different from using different cameras, where variation should be expected due to hardware differences.

As I understood it, the RAW conversion process (be it ACR or DPP) takes the Bayer matrix data from the RAW file and white-balances it and interpolates it. Oh, not to forget setting the white and black points and the curves...

I'd expect the series of RAW files described above, if processed through a RAW conversion process using a fixed white balance (not the one in the metadata, but an override) to produce essentially identical images.

- - -

Meanwhile, I don't understand the comment about making money from the RAW conversion software - Canon and Nikon give the software away, so they aren't making money from it. My estimation as to why they don't go to DNG is that they have too much invested in terms of software in their own formats, and don't see a compelling need ($$$) to move to a format pushed by a software company.

- - -

JPEG is a lossy compression. I want to be able to print from the data without the loss - I print from PSDs from CR2s. I use JPEG for creating small files for display online, but I won't print from those.
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Re: White balance in RAW - necessary ?
Old 06-20-2007, 04:54 PM   #19 (permalink)
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Originally Posted by CatCynic View Post
Meanwhile, I don't understand the comment about making money from the RAW conversion software - Canon and Nikon give the software away, so they aren't making money from it. My estimation as to why they don't go to DNG is that they have too much invested in terms of software in their own formats, and don't see a compelling need ($$$) to move to a format pushed by a software company.
This is really the bottom line. Jpeg and Tiff were both created after software companies got together and agreed to them. One of the last best things done in the cyberworld. Today many of these camera companies are run by middle mangers who no longer have the love of the image and only can see the bottom line. As they look at how much they have invested in software it does not dawn on them to cut this out and go with a common DNG format for the sake of the photographer.
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Re: White balance in RAW - necessary ?
Old 06-20-2007, 08:16 PM   #20 (permalink)
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Originally Posted by photoaz View Post
This is really the bottom line. Jpeg and Tiff were both created after software companies got together and agreed to them. One of the last best things done in the cyberworld. Today many of these camera companies are run by middle mangers who no longer have the love of the image and only can see the bottom line. As they look at how much they have invested in software it does not dawn on them to cut this out and go with a common DNG format for the sake of the photographer.
International standards get created for a variety of reasons and in a variety of ways (I speak as a participant in a number of standards activities, including chair of two working groups and editor of two published standards). Sometimes a consortium will be formed with the view of producing a standard; sometimes a proposal will be put up by a small group and others will be invited to participate in refining it.

It is rare for a single company to propose a standard and get it accepted. There seems to be a resistance to one company dictating to the rest. The usual way to address this is to gather the support of other companies before proposing the standard. Have you noticed Microsoft propose a standard and have it fail? Have you seen Sony create a standard like MemoryStick and have no one follow them? (Actually, Sony have a swathe of failed standards, as well as a number of successes)

There are cases where a company has produced a format that has become a defacto standard, sometimes against their will , but that is not the same as a company proposing a standard.

There are cases where a small group of companies has proposed a standard, and got it accepted, usually when that group contains key players (Microsoft + IBM can be a powerful force in computer standards). In other cases, the small group may thrash out a proposal, then invite other companies to join in proposing it to a standards organisation.

There are numerous standards organisations, and one path to getting a standard accepted is to put it through the process at one of these organisations. Organisations like the IETF, W3C, ISO, and CCITT.

As an example of a group proposing a standard, Microsoft and others proposed the "High Sierra" standard for the layout of content on CD-ROMs; they took it to ISO, and the proposal was modified slightly and became the ISO-9660 standard. For a while, CD-ROM creation software offered both formats, but eventually ISO-9660 displaced High Sierra.

It could be argued, and I don't know the details so I'm not saying this is so, that Adobe went about things the wrong way in trying to make DNG a standard.

Canon, Nikon, and others won't switch to a standard unless they can see a good reason to do so; if a large part of their market refused to buy products that didn't follow the standard, then they'd support it. If there's no compelling reason to switch, and they feel that keeping their own format gives them more freedom to innovate, then they won't switch.

I wouldn't hold my breath waiting for DNG to be accepted.
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