Hi all. Can someone give me some guidance please about setting levels, particularly input levels? I've been following Ken Lee's excellent notes on scanning, but am curious about a couple of things.
Firstly, in setting the output levels, we choose 0-255. I assume this is to preserve a full range of tones in the output, correct?
Now in setting the input levels, we are similarly seeking to capture all available tones from the negative. Herein lies my problem. In the histogram below I found I had to set the input levels at 19 and 222, to have a manageable print. Setting the upper level at 'b' produced an image which was almost blacked out. So what's the significance of this far end of the curve, and why does including it have such a profound effect on the image?
Similarly, at the other end of the curve the same may be true. In this example adjusting the lower level to 'c' seems to reduce some of the high tones, although the effect is not as strong as that at the other end of the curve.
The tone curve viewer seems to indicate the amount of linearity in tonal structure throughout the range, and I've noticed that the shape of the curve can be modified by moving the centre arrow. What is the common wisdom relating to making changes to the histogram before scanning?
Any help very welcome.
Baz.
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