To conclude a long story:
it was my intention to use photographs instead of (ink)prints for reason of quality and price.
The photoprint labo's I contacted all print at 300 or 400 DPI.
PopimsAnimator outputs 30 images at 600 DPI which means (I think) that there are 20 lenses per inch (LPI).
Using these lenses at 300 iso 600 DPI means that only 15 images are possible.
Since the size of the popimg print should remain the same it means also that the size in pixels has to be cut in half ( 960x579 iso 1919x1157 ).
Standard photoprints are 4 inch x 6 inch meaning that at 300dpi the popimg has to be put in a 1200x1800 pixel image.
To verify this I prepared a stereopair: I used 2 input images (no morphing involved)
and saved the interlaced image (1919x1157 pixels).
Then I made two reduced-size versions: one 960x579 pixel and the other 959x578
and put them on a 1200x1800 pixel image.
I sent them to 3 online photolabs that garanteed me to print at 300 dpi full size.
One of them is a professional site : they asked me to send the original 1919x1157 version and they garanteed that its photoprint would have exactly the size of the 600 dpi version.
Well, to cut this long story short: it did not work.
There is a lot of ghosting (one eye seeing part of the image destined for the other eye).
I also tried using morphing-animations with 15 frames: even worse.
My last hope was that there is a small variation in the quality of the lenses: I have ten of them and they all give the same result.
So, dear administrator, since this topic leads to nothing good, I have to ask you to remove all these 'Photo iso Print' entries from the forum.
If I ever find a solution I will tell you.
This will not be very soon however because I am a bit fed up with it right now.