Is the displayed maximum value with the black level subtracted or not?

Submitted by kevinjian on

Forums: 

Is the displayed maximum value of R/G1/G2/B with the black level subtracted or not?

As the image shown, the max pixel value is 15202, is the black level included ?

thank you.

Kevin

Image: 

All displayed values: image

Submitted by lexa on

All displayed values: image statistics, statistics for the selected area, values ​​under the mouse cursor, histogram - are shown in the current data processing mode.

If black subtraction is enabled - then black is subtracted (from everywhere). If disabled - not subtracted

Followup: on your screenshot

Submitted by lexa on

Followup: on your screenshot Min value is 0, it is not zero for Sony cameras if black subtraction is off. So: in this specific screenshot black level IS subtracted.

Thank you very much for your

Submitted by kevinjian on

Thank you very much for your answer. I also noticed that the minimum value equals 0, which means the black level has already been subtracted。

However, when I used Libraw to extract RAW data from an ARW file, I encountered an issue that I still can't explain.

I ran the following command using Libraw's executable `unprocessed_raw`:
```
unprocessed_raw.exe -4 -T input.arw
```
The output was `input.tiff`. In this file, I noticed that the maximum pixel value was **16596**, whereas in RawDigger, I saw **15202** (or **15204**). The RawDigger result was obtained with "subtract black" disabled, as shown in the screenshot below.

I'm puzzled about how the **16596** value was derived.

I've uploaded the input ARW file and the corresponding TIFF file for reference.

It's better to discuss this

Submitted by lexa on

It's better to discuss this with the file in hand. Please make it available (use any file sharing service, or send it to info@rawdigger.com).



unprocessed_raw extracts the full image, while your RawDigger screenshot displays image area only It is possible that the outlied value you mentioned is the value of a pixel outside the cropped (visible) area.

Answered in the E-mail.

Submitted by lexa on

Answered in the E-mail.

A short summary for other readers of this forum: when unpacking via LibRaw and RawSpeed (RawDigger's default), the data obtained for the ARW 2.3 format may differ slightly because LibRaw uses the linearization curve "as is" while RawSpeed uses dithering . From a practical point of view, there is no difference - the pixels differ by less than photon noise even for cameras with largest pixel capacity.

Thank you lexa. I understand

Submitted by kevinjian on

Thank you lexa. I understand in real photos, because there is natural noise present, we won't be able to see any difference between the curve processing methods of RawSpeed and LibRaw.

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