Dark slides

[holmberg]

Well exposed slides allways renders very dark, it can be seen in the input histogram, usually no value is above 170-180.
Is this normal?

Auto CCR or similar tool will of cause brighten the image, but shouldn't the image contain values closer to the 0-255 range before any correction is made?

OS: Windows 10 x64
OpticFilm scanner driver: 5.0.0.2
SilverFast version: 8.8.0r1(Plustek)_x64
Scanner: Plustek OpticFilm 8200i SE

[LSI_Ketelhohn]

Dear customer,

You must set the highlights and shadow. Either using the image auto adjustment or manually by moving the sliders in the Histogram.
The Histogram shows the entire range of values the scanner could see.
The image will be inside this.
This is because the scanner can see much brighter and darker values than actually present in the image.
Setting the highlights and shadows makes sure the actual image values are saved.

Kind regards,
Arne Ketelhohn.

[holmberg]

Thanks for the explanation, but I still wonder why the histogram is so narrow?, cause when i scan black/white negativ film the whole RGB range is filled out.

Can there be at problem with the driver or the scanner itself can be defect?

I can see that some others users here had problem with dark scans in the past, and it should have been adressed in the driver by now, but i'm already using the latest driver.

if i use the "image auto adjustment" will that degrade the scan quality? - I mean, it is a tonemapping, and it must be better to have correct exposure in the first place?

Kind Regards.

[LSI_Ketelhohn]

Dear customer,

That depends on the film and image.
The histogram you showed looks completely normal.
Some emulsions absorb more light some less.

Kind regards,
Arne Ketelhohn.

[robert32]

I have had the same problems. When scanning a dark negative, I can correct the problem by increasing the levels in Photoshop. Trying this approach with dark slides, isn't really feasible. The only workaround I have found is to scan dark slides as negatives in SilverFast, with an ISO of 50 (something like Ilford's Pan-F) and then inverting in Photoshop, and enhancing the levels that way.

Will changing the Histogram in SilverFast have a direct impact on the intensity at which the scan actually happens (i.e. does changing the Histogram change the hardware settings), or is it merely a software re-processing of the image once the scan is complete?


Regards,

Rob.

[LSI_Ketelhohn]

Dear Rob,

The highlights and shadows should be set, yes.
That will tell SilverFast which value is to be displayed as white and which as black.
The markers should be at the beginning and end of the curve.
Have you also tried to adjust the midtones in the gradation dialog?
That might be helpful if the highlights can not be moved very far without burning out image content.

Kind regards,
Arne Ketelhohn.

[robert32]

Thanks. Fundamentally, does it adjust the hanrdware of the scanner? Or does it just adjust the post-processing of the image once scanned?



Rob.

[LSI_Ketelhohn]

Dear Rob,

That would be post processing.

Kind regards,
Arne Ketelhohn.