Doesn't Vuescan do this as an option? I remember trying it when I was using an Arcus II, and I wasn't impressed with the results. Perhaps better tonality, but resolution was not increased and sharpness seemed to suffer. However, if tones are your thing, the sharpness can be adjusted in Photoshop as part of your normal workflow.
The rationale behind the Sinar scanning system is something very simple.
When analyzing an analogue image through a square slit, the blur induced by averaging the densities through this slit roughly corresponds to a cut-off period which is equal to the square size. Digitizing requires two samples per cut-off period, hence two samples per square size in both directions are required to extract all what is contained in the averaged image.
An hypothetical scanner with adjacent square pixels can only digitize with one sample per pixel size.
In the Sinar system, the whole pixel grid can be shifted by 1/2 pixel size in both directions i.e. (0, 0) (0, +1/2) (+1/2, 0) and (+1/2, +1/2) in pixel units. 4 passes combined together make the 2 samples per pixel size in both directions and allow to extract the whole theoretical resolution of an analogue image blurred by averaging through a square slit.
In principe, flatbed scanners can scan with double (or even more) sampling rate in the direction of the mechanical translation, hence in principle improving resolution by the theoretical factor 2, in one direction only.
One of the readers of the French MF+LF forum galerie-photo.info has tested a brand-new Epson 850 flatbed with an USAF 1951 target (both the Silverfast on silver halide film, plus another from Edmund Optics, chromium on glass) and has found the effective resolution to be ... worse in the direction of the mechanical scan, exactly the opposite of what should be expected ... I have no clue for this, except that the precision of the mechanical stage in the EPSON flatbed is probably not sufficient to allow the half-pixel sampling procedure with a good precision.
The results are explained here (text is in French but the scans of the target are visible images with no language barrier)
http://www.galerie-photo.info/forumg...7097#msg-57097
This type of thing might be possible with a high end scanner, drum, flatbed, or whatever, but I'd be very surprised if this would work with a consumer flatbed.
You often feel tired, not because you've done too much, but because you've done too little of what sparks a light in you.
― Alexander Den Heijer, Nothing You Don't Already Know
I've wondered about ways to use this principle with digital cameras. With pixel pitches now below 5 microns, this would hard to do with precision. But I've wondered if random vibration and other motions by themselves could cause shifts of a few microns, which might somehow be exploited.
With the Nikon LS 9000 and VueScan you can select 'Oversampling' up to 16x. At 2x the scan time already doubles, I don't want to know how long a scan with 16x oversampling would need. I've tried a 4x oversampling. Took me almost an hour for a 6x9 slide. The result: A waste of time. A better and rock solid tripod will deliver better results IMHO.
Yes it was PhotoAcute. I saw some images a friend did with this software and they definitely showed significant improvement.Originally Posted by fishbulb
Thanks,
Kirk
at age 73:
"The woods are lovely, dark and deep,
But I have promises to keep,
And miles to go before I sleep,
And miles to go before I sleep"
It is interesting technology. With a dslr film scanner, it would require a lot of extra frames, and there would be no specific camera/lens profiles. If you're willing to do that, you might as well scan at a higher magnification. For instance, I normally scan at 1x. Recently, though, I tested 5x with a Nikon Measuring Microscope objective, a very high quality optic. Yes, it did give slightly better results than a Apo Rodagon D at 1x, but in my view that added complexity wasn't worth it, at least for normal scanning.
You often feel tired, not because you've done too much, but because you've done too little of what sparks a light in you.
― Alexander Den Heijer, Nothing You Don't Already Know
Using a DSLR film scanner on a rock solid mount would definitely allow precision alignment of film to camera in 1 to 2 µm shifts as Emmanual suggests above. I use a micrometer X/Y stage calibrated in 2.5 µm increments which has a glass center area for light source projection from below. As long as the camera to film alignment is close to the 1 µm range and focus remains exact the pixel shift technique should work. Given that one ends up with say four images they must then be recombined with micronish accuracy to achieve a useable increase in resolution. All fairly formidable - I gave up on the task even though I was using an optical bench on a vibration isolation table.
Nate Potter, Austin TX.
Nathan & Emmanuel,
It seems like, in order to achieve real resolution increases, you would want to move the camera 0.5 pixels in between photos (like how the Sinar and Olympus systems move the sensor). Or in the case of scanning, moving the negative by exactly 0.5 pixels. If you moved it by exactly 1.0 pixels, then you would be capturing almost exactly the same data, and only reducing noise when you combine the files, right?
In practice it is unlikely that you would move the camera (or negative) by exactly a multiple of 0.5 or 1.0 pixels. Rather, it would be different every time. 0.33 pixels, 1.79 pixels, who knows. So there would be an element of luck to it. Perhaps there is a way to determine which images were moved the most closely to 0.5 pixels, and use only those?
I have a bunch of negatives in my scanning queue; I'm going to pick a few to do four 90 degree rotation scans and see what the results are. The rotation may be enough to capture real additional data, regardless of how many pixels are actually moved.
From toyotadesigner
With the Nikon LS 9000 and VueScan you can select 'Oversampling' up to 16x.
Thanks for the info!
I'm not familiar with the Nikon LS 9000 scanner, but I doubt that this is possible in both X and Y directions. My guess would be: oversampling, yes, but only in the direction of the mechanical translation. And doing 16x oversampling in that direction does not make sense to me, as I explained, the maximum reasonable sampling rate of an image averaged through a square slit is 2x with respect to the pixel pitch.
From fishbulb:
If you moved it by exactly 1.0 pixels, then you would be capturing almost exactly the same data, and only reducing noise when you combine the files, right?
Yes, exactly. And since resolution and noise are highly intricated when the human eye makes the assessment of what is a good image, multiple passes certainly improve overall scanned image quality, but not in terms of resolution, if the tiny sub-pixel displacements are not implemented with the utmost precision.
The question of "jitter" in the actual position of the sampling device is important. Clearly, in amateur-grade flatbed scanners this is a real issue. At least as far as it can be judged by scanning a test target on an amateur-grade flatbed.
I have no idea on how random deviations from 1/2 pixel, i.e. between 1/3 and 2/3 pixel for example, will have an influence on the final image reconstruction.
The brilliant idea of the day: testing the resolution of a drum scanner with a chromium-on-glass test target
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