dinasset wrote:
@Ofnuts
thanks for your detailed explanations. Now come my "stupid" questions: (I'm not a mathematician, so many of my questions could be "stupid"):
- assume the levels are adjusted such that they are just reduced 1:2 (for simplicity), so resulting values between 0 and 127 become values between 0 and 254, with "gaps" inbetween (0-2-4-6-....with values; 1-3-5-7...with no values); now:
1-how are the values "modified"?
2-why is it mathematically impossible to generate values inbetween? applying some kind of a smoothing mechanism like (for instance): there are 50 original pixels with values of 1 which should become values of 2, couldn't be a solution to keep 25 pixels at 1 and moving 25 pixels to 2? (on a specific request of the user, of course, because the resulting image looks a bit different )
@Rod
thanks, not yet, I didn't try it; but what you are saying is that in 2.9 even images 8-bits based are processed as if they were 16-bits based?
1) I don't understand the question
2) Because information is lost... the plugin just adds noise... Assume your image initially had better precision (12-14bits), so you can add some decimal places to the 1-255 values. The values that are at 120 in the 8-bit image would range from 119.5 to 120.5 in the original image. Now you apply some processing that stretches the values, so that 119 is converted to 128, 120 to 130 and 121 to 132. The gaps will be filled by taking some pixels with value 130 and assigning them values 129 or 131. But value 130 comes value 120 which itself represents the 119.5-120.5 range in the original image. So you can fill the gap at 131 with values that could originally be 120.5 (fine) but also with values that were 119.5 and would be much more accurately represented by 129 (ouch). And, of course, vice-versa.
To answer for Rod, in 2.9 when you process 8-bit images in 16-bit, you also initially start with 256 distinct values, but the problem is much less, because even if you create gaps, you don't lose colors. To use the example in the footnote my first post, in the high range your image starts with 128 distinct values, but you can map them anywhere in 26880 values instead of 105, so they remain distinct...