iSRD problem on chromogenic B&W negative

[NickJP]

I was scanning some chromogenic B&W 120 negs (Agfapan Vario XL), and found that having iSRD enabled was causing problems with highlights. See the attached 100% crops from one of the images. The blown areas are out of focus sky seen through leaves (look particularly to the right of the right-hand tree trunk). Scanner is a Braun FS120, Silverfast Ai Studio 8.2.0r3.

Without iSRD:

no_isrd.jpg (118.17 KiB) Viewed 812 times

With iSRD:

with_isrd.jpg (96.84 KiB) Viewed 812 times

[LSI_Ketelhohn]

Dear Nick,

Looks like the dense (dark) areas of the film block the infrared beam.
This is common for normal B&W films but can also happen with C41 film material.
For example if the material itself is very dense or if the material was not cleansed properly during processing.
You can try to use a mask to exclude these areas from correction or reduce the iSRD correction strength.

Kind regards,
Arne Ketelhohn.