iSRD artifacts on slides

[Etnoy]

Hello.

I'm scanning slides from the family archive. I don't know which film it is, but it's not Kodachrome or any speciality film.

Look at the attached image. I very often get these polygonal artifacts on one of the edges when using iSRD. What are they caused by? Any way to prevent them? I guess there is some kind of interaction with the slide holder and the infrared channel.



Epson v850 pro. Silverfast Ai.

[LSI_Ketelhohn]

Dear customer,

Please set the red scan frame as close to the image as possible.
iSRD is trying to "correct" the slide frame because the infrared channel can not penetrate it and it therefor is being detected as a defect.
The frame has a protection area close to the border of the frame to prevent this.
But it only can work if the frame is placed tightly around the image.

Kind regards,
Arne Ketelhohn.

[Etnoy]

Thanks, that answer makes sense. I am still struggling with framing, as the auto-detection really has problems detecting the slides in an usable way.

[Etnoy]

OK, I have now tried to put the frames tight around the slide. However, the issue is still not gone and there still appears large polygons at one of the edges. Strangely, it's usually just one edge and not several.

I crop the red area to be very very slightly larger than the image as I prefer cropping in Lightroom, but this time the problem is still happening.

[LSI_Ketelhohn]

Dear customer,

If you create the frame larger than the image, that is why this is happening.
That is why I wrote it is important to place it tightly around the image.

You can check this in "mark defects" mode while the 1:1/HQ preview is active.
The red marks should start a little bit off the actual boarder of the image like this:

Screen Shot 2016-04-26 at 10.47.29.png (97.8 KiB) Viewed 892 times

Kind regards,
Arne Ketelhohn.