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Old Apr 23, 2005, 8:12 AM   #21
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I thought the bits/channel was the number of steps, but had nothing to do with the dynamic range. Much the same as a set of stairs (bits) going up a specified height (dynamic range). That could be done with 8 steps (bits) or 12 steps (bits), but the height (dynamic range) would be the same.

So the number of bits does not necessarily have anything to do with dynamic range. It might or might not depending on the camera.

Or do I have that all wrong?
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Old Apr 23, 2005, 9:27 AM   #22
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Yes, we sort of speak the same thing, there is the dynamic range (light to dark)the physical sensorin the camera is capable of; then there is the range (number of steps)possible in the output image. So both the jpg and the raw are mapped from the original sensor data, one gives you access to the full data produced by the sensor, and one squeezes down or throws away a large chunk of theinformation.

Article from a famous site on bit depth http://www.steves-digicams.com/techc...pril_2005.html

Another article on benefits of editing in 16bit vs 8bit http://www.earthboundlight.com/photo...ifference.html

Still I think everyone else should be using jpg .:G

Peter.


PS:Just in caseI disappear for a while, assoon as I finish my Taxes (we have a few days to go here, before big brother starts knocking);I am replacing my motherboard with a 64-bit board. If I vanish for a bit, youknow something did not go exactly right. :roll:
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Old Apr 23, 2005, 9:01 PM   #23
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I agree with BillDrew (& others.)

While you are not *actually* adjusting exposure, there is something different going on when you start with something that has been down sampled (even in a very intelligent non-linear way - the 12-bit raw turned into a 8-bit JPG incamera) vs. taking the same number and maping it into a larger space (the 12-bit raw left that way incamera and turned into a 16-bit image in memory after RAW conversion.)

You don't get any more range (a blown hilight is a blown hilight) but you can effect how that mapping is done by playing with the exposure so that details that were lost 'cause they were too dark can be teased out. Or things that would get mapped into a blown hilight can be maped so the detail is preserved.

The reality is this. If you are good enough, you don't need RAW. You'll get it right in-camera (which should be the goal of everyone any ways) and then you'll just size it as necessary and print (or whatever.) But most people aren't that good. They make mistakes.

Or in my case, not only mistakes some times but the ever changing world makes it near-impossible for me to get it "right" in-camera. Say the sun comes out from behind a cloud. I guess I could be good enough to dial in some exposure comp while also trying to get the perfect head angle of the bird. I'm good, but not that good. I'd rather focus on the perfect head angle and fix the slight-missed exposure in PS.

The arguments about if you "need" RAW is a question of standards and your abilities. For me, I can produce better results by using RAW. It also makes my life easier. But to say "I know a pro that uses JPG and produces great stuff" is like saying "I know a professional basketball player who can whip anyone in one-on-one with sandles on." Maybe, but I'll still play with the proper footwear until I get to his level. JPG is faster & smaller... but I do better with RAW.

Eric
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Old Apr 24, 2005, 1:09 AM   #24
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A question for DBB.
Shooting with a 110lb dog sounds difficult. Wouldn't it be easier to use a camera? :blah: lol

Suzan
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Old Apr 24, 2005, 1:14 AM   #25
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And some people complain about a couple pounds of camera gear! :-)How many megapixels is the dog?

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Old Apr 24, 2005, 8:58 AM   #26
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ImKayd1 wrote:
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A question for DBB.
Shooting with a 110lb dog sounds difficult. Wouldn't it be easier to use a camera? :blah: lol

Suzan
I will now deal with my political opponents of both the right and left....

My dog, is a commercial brand, combination White Balance dog/photographic assistant....

For those who have ever set their white balance in the field would know, that a VERY large WHITE dog is of immense importance - :blah: - So much for that!

Now, as for you others, you guys absolutely ignore the question of F-stops and my tests. "A blown highlight is a blown highlight," is not an answer. I suggest doing the folowing:

Shoot in RAW on a white target and shoot under and over proper exposure. Do this in both JPEG, TIF and RAW.

Than process the images and see what happens!

dave:evil:
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Old Apr 24, 2005, 10:05 AM   #27
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AHA! I'm a little bit right....

Here is a carefully editied excerpt from my original post, only those part of my post that are wrong are being thoughlessly left out for some reason...

"When you use RAW, It's NOT quite as good as actually having the right exposure level. You are doing what someone in a darkroom would do, by pushing the film or it's opposite. So all RAW importers allow 4 stops of play in either direction.

I've found (as the article I read mentioned) that the practical level or results is 2 stops. past that, you get to much noise. You get noise ANYWAY, but the noise is not really objectionalble."

Now here is an explanation from a tutorial on RAW, link posted below below:

Exposure Compensation

Some photographers have mistakenly thought that RAW allowed them to correct exposure errors. Well, to a limited extent, that is true.

However, a picture has to be correctly exposed, whether you are using RAW or not. You cannot take a grossly underexposed or overexposed picture in RAW, and expect to be able to "correct your mistakes."

To explain how this is possible, we need to get a bit technical: While JPEG captures 8 bits of colour per pixel or 256 shades of colour per pixel (16.7 million colours), RAW captures 12 bits of colour per pixel, translating to 4096 shades of colour per pixel (68.7 billion colours). This great amount of information (extra pixel depth going from RAW to JPEG) is what allows the exposure to be corrected up or down by one stop, and sometimes by as much as 2 stops (but you might be pushing your luck). Applying this exposure compensation and adjusting the other settings to your RAW data in post-processing may be enough to salvage an otherwise ruined image.

http://www.photoxels.com/tutorial_raw.html
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Old Apr 24, 2005, 12:59 PM   #28
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I have a friend who shoots while walking his dog... the problem is that his dog is about 3/4 sheep dog. He has to stay away from large groups of people or his dog starts to herd them. It's funny to watch, until he starts to do it to you.

And I'm not going to ask which end of the dog you look into and which end the light comes in. No, lets just not go there.

DDB
We agree, that adjusting exposure with RAW isn't really adjusting exposure. Its changing the mapping of the data you have so that what would have been mapped into a blown hilight (or too-dark shadow) is instead mapped into a color & brightness that isn't blown out.

I just had another thought. One problem I've seen with adjusting exposure via RAW is that a slight color shift and some color bleeding can occure. Things get a fridge of color around whites that can be really annoying. It doesn't seem to always be there, but I've seen it. Damn annoying to remove, too.

Eric
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Old Apr 24, 2005, 2:25 PM   #29
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You might find this interesting...

http://www.luminous-landscape.com/tu...se-right.shtml
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Old Apr 24, 2005, 3:37 PM   #30
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peripatetic wrote:
Quote:
You might find this interesting...

http://www.luminous-landscape.com/tu...se-right.shtml
Very! Thanks for the link. In find, that this is indeed what I was doing, but through trial and error.

In any event, it explains quite well why people whould use RAW, in any serious digital photography.

dave
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