Underexposed slides?

All the problems with Plustek film scanners

x11
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Scanner: plustek OpticFilm 8200i AI
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Underexposed slides?

Postby x11 » Sat Aug 12, 2017 6:50 am

I'm trying to scan slides, and I'm finding the scans consistently come out at about 2-3 stop underexposed. When I put the slides on a light table with a loupe, I see the most detailed, beautiful results, but when I scan them they look muddy and terrible. If course, I can easily adjust the histogram to boost the scanned image, but the dynamic range and contrast suffer and the noise increases. I've encountered this with Silverfast Version 8.8.0r9 and the version V2.0.0.0 of the scanner software as provided here: http://downloads.plustek.com/downloads/english/Patch/OpticFilmSeries_V2000_1L.dmg

I'm using Mac OS 10.12.5.

What gives? Is there any way I can adjust the lamp brightness or increase the exposure time?

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LSI_Ketelhohn
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Re: Underexposed slides?

Postby LSI_Ketelhohn » Mon Aug 14, 2017 8:55 am

Dear user,

devices supporting exposure adjustment offer analog gain in the preferences' special tab.
Please note that this is only possible for positive scans and when Multi-Exposure is deactivated.

Kind regards,
Arne

bruno_s
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Scanner: v500
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Re: Underexposed slides?

Postby bruno_s » Wed Aug 16, 2017 3:39 am

scanner: V500
IOS 10.10.5

Hi,

I am having the same problem underexposed scans i would say 90% complete dark. I am using HDR mode, without HDR mode the scanner works ok, but once its in HDR mode its scanned complete dark. The frame its ok on light table and even in the preview.

I am using this software for years, the process its the same that i used to.

And just update the latest version and when zoom in the frame its crop by itself. (see attachment image01_zoom_in and image02_zoom_out)

sincerely
Attachments
HDR versus preview normal scan.jpg
HDR versus preview normal scan.jpg (470.54 KiB) Viewed 113 times
image02_zoom_out.jpg
image02_zoom_out.jpg (363.42 KiB) Viewed 113 times
image01_zoom_in.jpg
image01_zoom_in.jpg (470.54 KiB) Viewed 113 times

x11
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Scanner: plustek OpticFilm 8200i AI
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Re: Underexposed slides?

Postby x11 » Sat Aug 19, 2017 4:02 pm

I see. If a scanner supports Multiple Exposure, then it stands to reason that it should also support Analog Gain, or something analogous, no? Using the Plustek 8200AI, I'm able to use multiple exposure to achieve increased latitude, and when I watch the preview window while scanning ME I see both a dark and light image. The scanner driver clearly supports increasing the exposure time since the second ME pass takes a good while longer than the first.

To avoid getting too far off field, my main concern is this gap on the right-hand side of the histogram:

Image

With a white point set as in this image, I can imagine two possible implementations. On one hand, SilverFast could use standard digital postprocessing to multiply the already-sampled pixel values, thereby brightening the pixels but boosting noise in the process. On the other hand, SilverFast could increase the exposure time on the scanner, achieving something similar to the practice of "exposing to the right" on digital cameras and significantly reducing noise. Which of the two does SilverFast use?

Whenever I look at my slides on a light table, I notice a fantastic degree of detail in the shadows, and I'd love to use SilverFast to be able to preserve it.

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Re: Underexposed slides?

Postby LSI_Ketelhohn » Mon Aug 21, 2017 9:18 am

dear bruno_s

I have not seen this before. Have you tried resetting SilverFast to factory defaults?
If not please try that.

Kind regards,
Arne

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Re: Underexposed slides?

Postby LSI_Ketelhohn » Mon Aug 21, 2017 9:23 am

Dear x11

No, a scanner supporting Multi-Exposure must not necessarily offer analog gain.

Your image unfortunately did not reach me. However an empty area in the highlights of the histogram is completely normal and should be there.
The scanner has a much wider range of brightness then available in the image. Especially in the highlights. The emulsion of the film will always absorb some light so it will always be darker then all light of the scanner reaching the sensor.

Kind regards,
Arne


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