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12/17/2005 09:50:35 PM · #1 |
in november, my camera was at the canon service center for a month. It left me more time to think about photography and allowed me to understand things about RAW. Here are my conclusion and the questions remaining. First, it's incredible the amount of image information that are lost by shooting JPEG. For exemple a JPEG fine on 350D is about 2-3MB while the TIFF (uncompressed file) file is 22.8 MB and this is only 8bits/channel when you're at 16bits/channel the TIFF is about 45MB. Every single bits of compression become lost of information, some pixels value are changed for other pixels value in order to save blocks of pixels instead of each pixels values. The in camera workflow includes many steps that destroy valuable image data. Here are the ones I know of.
1. White balance. Not really data lost but interpretation of light values that can be good or not. Anyway this is irreversible in JPEG.
2. The camera is applying sharpening. DATA LOST. Some pixels values are changed to give better sharpness to the image automatically destroying some captured data. Sharpness is inevitable in digital imaging but is the amount and radius and threshold in the camera good for this particular picture? plus sharpness can products halo. the effects are irreversible.
3. The camera is applying contrast value. DATA LOST. there are some shadow that become plain black and some highlight that become pure white wich they were not. the effects are ireversible.
4. The camera is applying saturation value. DATA LOST. Given the subject, lighting and exposure, some clipping may occur wich is when saturation become so intense that some minor color variation (information) disappear to become bright red or yellow etc. without the détails that should be there. Irreversible.
5. The camera the save the file as a 8bits/channel JPEG, first averaging the pixels to 8 bits value(DATA LOST) and then compressing the files to save block (DATA LOST).
You end up with a files that originally captured billions of colors and that need 45.5MB to be saved compressed to 2/3MB and all of these operation are IRREVERSIBLES.
I also suspect the camera to apply other value as well (i.e. shadow control and brightness control in ACR) but I have no proof of it.
When the camera was back from canon I made some test and I found out that it is possible to take a RAW files and to convert it in a way where there are so many images data remaining that it can compete with an HDR image made with photoshop combining multiple exposure.
The question I still have is what is the headroom when shooting in RAW to recover from overexposition or underexposition.
Also if somebody have comments or a complement of information about what's in this post feel free to post. I NEED to know all there is to know about RAW files and in camera processing.
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12/17/2005 09:56:50 PM · #2 |
You're right! Expose to the right and you'll get the most info out of your RAW files.
HIGHLY recommended book about RAW processing.
Informative blurb on RAW on Luminous-Landscape.com
Message edited by author 2005-12-17 21:58:37.
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12/17/2005 09:58:12 PM · #3 |
| If you can buy Camera Raw with adobe photoshopcs/or cs2, do it. the author did a fabulous job. www.peachpit.com or www.adobepres.com. best $35.00 I have ever spent. |
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12/17/2005 11:05:12 PM · #4 |
Here are some exmples of the huge amount of data you can get with RAW that are lost with JPEG's.
This one is strait from the camera set at parameter 2 (every parameters set to neutral) shot in adobe RGB and converted for web
This one is proceesed from RAW in ACR (only exposure compensation) and then processed in Photoshop (16bits/channel) just like it would have been in camera but with all the information (no contrast or anything at this stage) for me to choose what I want to do with it.
comments? |
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12/17/2005 11:23:02 PM · #5 |
| shoot in raw 45 megs shoot in jpg 4 megs 41 megs LOST! ;) |
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12/18/2005 12:24:33 AM · #6 |
the uneditied image is better.
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12/18/2005 12:47:36 AM · #7 |
Originally posted by soup:
the uneditied image is better. |
I kinda agree, straight from camera at least at this size and resolution looks better. hummmmm |
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12/18/2005 12:54:07 AM · #8 |
I prefer the cooler WB from the first one but the 2nd one brought out more detail in the shadows.
bazz. |
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12/18/2005 09:07:04 PM · #9 |
Originally posted by soup:
the uneditied image is better. |
This is not the point. The point is starting from image number 2 I could edit to the image number 1 because it carry more information. But starting with image number 1 I could never get to the image number 2 because the picture data as been lost in camera. I'd have to draw it. Besides, I do prefer image number 2. It's much more like what I saw with my eyes when I was there. |
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12/18/2005 09:20:58 PM · #10 |
ok, I have only a small amount of input.
1. no matter what you shoot, exposure is crutical. more so with digital than with film
2. RAW files are the way to go if you have the space for them. If you know what you are doing with them, they are paradise, but nothing can ever compensate for good exposure |
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