Ghost picture visible in stack

Hi all,

I need to analyze a set of frames from a movie. I did that before by handling each individal frame image in a macro loop.

Because it is probably more efficient I now import the image sequence to form a stack. I am very surprised that the results are now different.

When I have a closer look at the individual slices, by “scrolling” through the stack with Next slice or the arrow keys, I see that in every slice I can also see a low intensity view on the next slice. When I do my analysis I notice that this “ghost” picture is also taken into account in my results.

How can I prevent this? Did I miss some setting ?

Thanks ,
Fred

Hey @Fred_ckx,

can you share an example image and details about the analysis you do? Otherwise it’s hard to point you in the right direction :wink:

Cheers,
Robert

Here is a screenshot of one of the images in the stack. I want to determine the ratio of the pink area (to the right and the gray area to the left. Here it should be about 1:3 . The area in the middle now contains a “sneak preview” of the next picture in the stack. My original pictures, befor importing them as a sequence only contain 2 regions.

There is one additional step after I imported: I reduced the resolution of the stack as a whole with Image>Scale… by a factor of 2 to reduce computation effort. Maybe there is a clue, because of interpolation or so between the slices?

Fred

Hey @Fred_ckx,

If you scaled in time with some interpolation, such effects can occur. Would you mind trying again without scaling in time dimension?

Let us know if this helps!

Cheers,
Robert

I am having a look now into the step where I reduce the resolution. There is an option “Average when downscaling”. I thought that averaging would take place between the pixels in one slice but not in the Z-direction. Nevertheless, when I try different settings for this I can not reproduce the behavior :frowning:

My pictures now look OK. Which is good…

I wonder when this problem pops up again…

Thanks anyway Robert!

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