Noise in areas with even colour

[hanfeh]

I have scanned thousands of colour slides with my plustek OpticFilm 7200 scanner with good results. I recently started to scan my colour negatives using NegaFix (ver 6.4.4 of SilverFast SE) and discovered a kind of noise that looks like dust particles or very thin lines in different directions. The noise is white or very light in areas with an even tone like a blue sky. As far as I understand this noise is related to the inability of the scanner to distinguish between small variations in these even areas in the negatives. The noise is not related to any special type of film or chosen resolution.
Do you have any hints to avoid this type of noise that in some cases look like an even layer of dust on parts of the pictures. I am very careful to remove all possible dust from my negative film.
Hasse

[LSI_Morales]

Dear Hasse,

The "noise" you described might be the film grain. For that you might want to use the GAIN filter. If the "noise" is not film grain but in fact produced by the scanner.

You might want to use Multi-Sampling or Multi-Exposure.

Cheers

[hanfeh]

Thank you for your proposals. The "noise" is not the film grain. I have seen descriptions of this in other forums so it is not totally unknown. It appears in areas with smooth continuous tones. The "noise" has identical positions in the picture why I don't think the Multi-Exposure will do any difference. It is a kind of artefact produced by the scanner. But it is not random electronic scanner noise.
Looks like editing with different tools after the scanning of the negatives, is the only way to reduce this kind of "noise".
Hasse

[LSI_Morales]

Dear Hasse,

I suggested Multi-Exposure or Multi-Sampling because they help reduce the random noise generated in dark areas or smooth areas. However you say

It is a kind of artefact produced by the scanner. But it is not random electronic scanner noise.

If you are saving your files as JPG there is a possibility that the format compression helps increase this kind of noise in smooth areas. I would save the files as TIFF files without compression, perhaps this will give you a better transition of subtle tones.

Bear in mind that some image viewers just clip images for the sake of speed. You might also check with different image viewers and in 100% size applied to it.

Cheers