Interpolation on PF1800AFL?

[JohnHaines]

I have just switched to using SE 6 instead of Cyberview with my PF1800AFL after being very disappointed with the results I was achieving. I appear to be getting a lot of banding occurring, especially on dark areas of slides.

In SE 6 I have discovered that I can set the scanner to work at 3600dpi. The scans certainly take longer than at 1800dpi. The resulting files are also 4x the size of an 1800dpi scan. The resulting images are significantly better than those from either SE 6 or Cyberview at 1800dpi. All banding and similar noise effects appear to have dissapeared.

What is happening? I assume that SE 6 is getting the scanner to interpolate its data. It cannot really be scanning at a true 3600dpi ... can it?

John

[LSI_Flyvbjerg]

The highest resolution in SilverFast is the double of the optical resolution of the scanner. In your case 3600 dpi. The file size will increase by 4 times, that is correct. SilverFast is still scanning with a maximum resolution of 1800 dpi, but is interpolation up to 3600 dpi.

It wonders me a little that the image quality should get better taht way

Eric.

[JohnHaines]

[quote="Eric Flyvbjerg"]The highest resolution in SilverFast is the double of the optical resolution of the scanner. In your case 3600 dpi. The file size will increase by 4 times, that is correct. SilverFast is still scanning with a maximum resolution of 1800 dpi, but is interpolation up to 3600 dpi.

It wonders me a little that the image quality should get better taht way

Eric.[/quote]

I thought it might be something like that. How does it do its interpolation? If it is entirely software based I am impressed by the algorithm used as it is FAR superior to the effects of bicubic resampling an 1800dpi image up to 3600dpi in photoshop elements 2. Also, this doesn't entirely explain why the scan phase takes longer, i.e. scanning the same slide at 3600dpi takes apx twice as long as scanning it at 3600dpi using SE 6.

John

[LSI_Muenier]

Did you see the "banding" (what does it mean?) at 1800 dpi in SE 6, too (or only Cyberview)?
Please make sure to "drive the scanner warm" by some test scans, as it appears to me that there is some scanner drift right after it has been powered on.
Please inform me on this: What is the maximum resolution you can choose from SilverFast's resolution slider?

Martin.

[mjb]

If you care to take a quick look in the Microtek Film Scanners area, I posted a message on exactly this subject, but for the Microtek Filmscan 35 (the same hardware, rebadged).

So far support have said it is related to the Cyberview driver DLLs (which Silverfast depends on in some way). Although reinstalling CV did not help.

Oddly, Cyberview doesn't produce these bands. Well, not in "quality mode". Silverfast does. And silverfast only ever scans in "draft" mode (i.e. the faster/lower 1800dpi). That's the real problem, I think. Cyberview scans in "quality mode" or "draft", and it bands in draft, but not in quality.

I will attempt to do some scans on 3600 and see what happens to mine. It certainly does make dark transparencies and negatives unusable when it happens. If this is the solution, it would be good to know.

To see the "banding" there are 3 examples in my post on the other forum area at http://www.silverfast.com/forum/viewtopic.php?t=1334

[LSI_Muenier]

SilverFast relies on low level drivers from Pie, but unfortunately they are not used by Cyberview. So, installing Cyberview doesn't change SilverFast's behaviour.
Thank you very much for your information about your comparison between Cyberview draft and quality behaviour. This will be very useful to clarify with Pie how SilverFast can use the same scan mode as Cyberview drives the scanner. I have requested such information from Pie.

Martin.

[mjb]

Martin:

I didn't entirely understand the advice either, but was told to reinstall the Cyberview driver to cure problems in Silverfast. It didn't help, but I tried it anyway (desperation).

From support :-

"What version of CyberView is installed in your Win98? If it is not the
latest one it might have installed out-of-date driver files which are also
used by SilverFast. Visit http://www.microtekeurope.com/driver_download/
for updates on Cyberview software. Your Cyberview version should be 2.41"

and for other questions raised to do with grainy pictures and unpredictable colour casting on scans through SF. (esp. where the exposure has been changed)

"can also be traced back to Cyberview installation."

I can understand that Silverfast may rely on a PIE supplied DLL, is this not a DLL that also ships with Cyberview then?

It would be really naughty if Cyberview went "under the hood" to get to a quality scan mode that was not presented to developers through the DLL, so that no competing application could use it. That's not a nice way to develop things ...

[JohnHaines]

The banding that I have been getting looks like an interference pattern, not the same as shown in the example images in the link supplied elsewhere in this thread. I find that it is more likely to happen when the scanner is first switched on or if it has been sitting idle for a while. Even then, it is a lot more visible if the output resolution slider of the frame tab is set to 1800dpi.

The typical settings that I use at the moment for my Agfa ctx 100/200 slides are:

Horizontal and vertical scale left at 100% and the output resolution set to 3600dpi. This leads to a file size of 50.55Mb without any cropping.

Colour adjustment depends upon my mood and the slide in question. With a reasonably balanced slide I sometimes find it easier to just scan the whole frame and then crop and adjust it in Photoshop Elements 2.

I would like to mention that I am very much a newcomer to digital imaging. I have only been trying to archive some of my slide collection for a couple of months now. It still takes me a lot of effort just trying to work out which adjustments to try and achieve something that looks even close to a projected image!