Stripes and lines in dark plain areas

[asto999]

Hello everybody,

when scanning positives that have larger dark areas of a more or less plain colour (or shadow, at all), I detect patterns of lines and stripes within that dark "shadow" zone having different colours. It seems to me somewhat like a CCD pattern or something like that.

Please cf. the following two examples (details from larger images):

The first example seems to be composed from several image stripes, which can be seen in the plain dark blue area (the sky).

The second example shows coloured stripes in the lower left corner (shadow area).

Has anybody got an idea how this comes from and how to fix it? Scans having such lines are worthless.

Thanks and greetings,
Armin

<img src="/img/forum/example1.jpg">


<img src="/img/forum/example2.jpg">

[asto999]

I just found an opinion that such stripes may come from multiple-CCD and their noise (hence only visible in very dark areas).

Has anybody experienced such a thing?

[rsfoto]

Hi,

There is under OPTIONS > SPECIAL a little menu called Limit Gamma Slope. UNCHECK this and try again.

Long ago I also had that problem and with this unchecked the stripes in dark areas disappeared.

regards

[asto999]

Hi Rainer,

Thank you for this hint. But I am not quite sure if I fully understand the following:
I use AACO. As I understand it, AACO limits the gamma slope, too.
If I disable gamma slope limiting, I disable AACO.
By the way: I wonder if this checkbox is there - I thought I did not see one and I am not sure if this is caused by the presence of AACO.
I will do some tests and try different settings this weekend.

Best regards,
Armin