Problem with the selection frame

[christianm]

Hello,
My problem is this : After a preview of 2 6x6 negatives stripes, I of course use the frame to select the images that I want to scan (negafix settings is Portra 160 VC 6x6).
After setting a frame for one image, if I move this frame on another image (or just move it a little bit) and move it back on the same image, levels are different. See the 2 printscreens attached. The number 2 seems more accurate.
Why that ? Can someone help me on this ?
Thank you.

01.jpg (394.41 KiB) Viewed 800 times

02.jpg (400.98 KiB) Viewed 800 times

[LSI_Ketelhohn]

Dear user,

Negafix automatically adjusts to the negative histogram for the conversion. For best results make sure the red scan frame is set tightly around the image content. Unexposed material or empty space like in your sample can disturb the histogram.
For situations where you want to transfer levels you can disable the auto setting in NegaFix (in the expert settings expansion dialog for Ai Studio).
But remember that this only will work correctly for very similar images or if an image has to be scanned in several steps. The mor images vary the more likely it is that disabling the auto function can result in the loss of dynamic range.

Kind regards
Arne