Descreening vs. GANE

[pmitterboeck]

Hi!
I've one question concerning grain reduction when scaning negatives.
On the silverfast homepage I've found an article dealing wirh this topic. There zhe author used the descreening option set to about 3900 lpi with a scan resolution of 3900 to 4000 dpi. Additionally he used the USM tool. I tried this too and the result is really very good! I'm not sure if I can reach this quality of noise reduction and sharpness using GANE. On the other hand, I thought that GANE is the first choice for this problem.
Pls can you describe the difference between these methods?
A little bit of technical background would help!

Greetings,
Peter

[LSI_Noack]

Dear Peter

GANE is a tool to reduce color noise. Alternatively, the multi-sampling options provided by SilverFast (in the SE and Studio versions now also independently of hardware) can even substantially increase the scanner ability to generate image with low to now color noise.

Sharpness is best affected by USM.

Kind regards
Sonny Noack
- tech support, LSI AG -

[pmitterboeck]

OK, but in a color negative grain is a result of the resolution of the color layers of the film. So e.g in a sky I get points with different colors from magenta to green and I like to correct this to a homogene area of blue/cyan.
For my undestanding this is a problem of grain of the color reversal film and my question is which of the mentioned methods leads to better results and why.

Greetings,
Peter

[LSI_Noack]

Dear Peter

sky in a colour negative probably is (after the conversion to a positive image) a relatively high-lighted part of the image.
The original negative film material therefore has a relatively dark part of sky.
Shadows mean to a scanning software that detail contrast is low and needs to be amplified. This increases the effects of CCD typical artificial grain resulting in individual red / green / blue pixels significantly more saturation than the pixels surrounding them.

Perhaps this comparison does make it clearer:
Imagen a radio broadcast. The station's signal is very badly received, resulting in a low volume and some background noise. Now you increase the volume using the amplifier. You will not only increase the meaningful data (the broadcasted song or news), but also the background noise.

However, while this artificial colour noises is inherent to the CCD technology, it can be overcome to a certain degree with multi-sampling.
As this noise appears erratically, multiple images will enable the scanning programme to sort out the erroneous values and reduce overall colour noise.

I suggest you want to read on:
http://www.silverfast.com/show/silverfa ... ng/en.html

Best regards
Sonny Noack
- tech support, LSI AG -