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DPChallenge Forums >> Photography Discussion >> Adjust contrast or not?
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 02/23/2006 06:48:46 PM · #1
I am wondering if it's generally a 'policy' to adjust levels (or other method) on photographs that are missing information in the last say 2/3 - 1 1/3 stops.

What if there is a risk of brightning the subject too much?

What if it's a picture of a book?

Sorry if these question seem vague. I just recently took a photograph of a book with pages open; after many confirming pieces of equipment (Pentax Spot meter, Grey Card, 20D meter, F1 meter) all confirmed my exposure, I ended up with an exposure, while technically true - had no information in the last stop of the high end of the histogram.

Cool enough I suppose, but I thought the pages would be white. But they were off white.

And I've run into this question before. Now I am trying to get a better idea here, should I put a constant step in my workflow to adjust the contrast to realize the full latitude, regardless of initial feelings. (You know, some days you like warm, others you like cold)

-CN
 02/23/2006 07:55:40 PM · #2
When I am taking a photo of a subject with too much white, I always over-expose by 1 stop or something similar... this I think is something to do with camera metering trying to expose to make everything 18% gray...
 02/23/2006 08:01:51 PM · #3
I used a grey card. Even with a grey card you may get a low contrast image. I am wondering about adjusting the contrast as a policy in images I guess this may be to broad a subject to answer.

I am on the fence about leaving things alone (adjusting contrast) or standardizing the constrast adjustment to encompass a fuller range.

-CN

02/23/2006 08:04:15 PM · #4
There are two issues here...
- How the image is originally exopsed in the camera
- How it's post-processed
Let's start with the end... not all images need to have pure whites (or pure blacks for that matter). The majority look better with a full range of tones, but it's not a hard & fast rule. An image without a full range of tones will look lower in contrast (of course) and that's just what's called for in some cases. Now for the first consideration, exposure...
With film it was virtually always the goal for the original exposure to be as close as possible to the end result. If the look you're going for is "low key" with no pure white tones, nor for tha matter any tones in the upper third of the range, then you'd expose that way. With digital, you get better results by exposing so that the brightest tones are just short of clipping and then pulling back exposure in post-processing. You'll get lower noise and better detail in shadows by far, as well as more flexibility in post processing.
As an aside to all this, if you have a photo where you want the brightest tones to be nearly pure white, but still want to darken the image globally, use curves, and set the white point as desired (move the top right endpoint of the curve to the left) and then pull down the middle of the curve to darken without changing the white (or black) points.
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