The title says it all. If we scan multiple times but bump the source slightly in some way can we get an effective increase in resolution?
Darin
The title says it all. If we scan multiple times but bump the source slightly in some way can we get an effective increase in resolution?
Darin
Theoretically, yes. In practice, I'm not aware of a very user friendly way of processing the different scans into a higher-res end result.
If the system isn't repeatable and precise, then it will lead to less resolution. You can clearly see this if you use multi-pass scanning on many systems. The idea here is to increase dynamic range and lower noise, which may happen, but all too often it leads to soft scans. Multi-sample system do better in this regard. Move the area sampled. Take multiple readings and combine them in some way. Move to the next area.
“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 think Koraks and Peter are right. It should theoretically be possible. The equivalent gets done in video, for the purpose of enhancing detail for surveillance work etc.. But I haven't found any software that accomplishes this with still images.
Has anyone tried using a focussing stack algorithm on multiple images with the same focus?
It won't work with focus stacks if the focus does not change. The software looks for overlapping areas where focus goes from in-focus to OOF, and selects the sharpest areas from overlapping images. If it does not detect a second image with sharper pixels, it will not blend.Originally Posted by paulr
You can get an increase in real resolution if you can change the angle of reflection between scans. E.g. rotate a print with a textured surface 90 degrees with each scan, and sum or difference the layers in photoshop. I don't know how to apply this to negative scanning, unless you are dealing with a scratched negative that only shows some scratches at some angles and not others.
In this thread: http://www.dpug.org/forums/f6/aztek-...perience-2314/ Tim Parkin mentions doing two scans of one negative with different settings, effectively scanning the shadows in one and the highlights in another, and then merging the two images in photoshop to create a high-dynamic-range image. So it can be done for increased dynamic range. With Photoshop's "Auto-Align Layers" tool it would be easy to align multiple images, and then use an HDR plugin (or Photoshop's native HDR tools) to merge the layers to create the final image.
As Will says, if you want to do it to increase resolution, the images (or the scans) have to be different in some way. It's just like doing it with the "new" Olympus technology (available in Sinar digital backs for many years) to generate 40?MP files with a 16MP sensor. It takes a series of images and moves the sensor in the camera around a tiny amount before each image. So each image is very, very slightly from a different angle. Then the camera merges the images together to form a higher-resolution file. It's like doing panoramic stitching, but the images are 99% overlapped.
If you want to do this with a scan of a negative, supposedly it CAN be done. In this thread http://photo.net/film-and-processing-forum/00b6OH there is some evidence that merging multiple scans of the same negative, with the negative shifted on the flatbed each time it is scanned, can be merged and increase the total resolution. Here's another example: http://www.rangefinderforum.com/foru...d.php?t=130731
Here is pretty clear evidence that this can work: https://farm9.staticflickr.com/8346/...6f764c02_h.jpg The upper left is one scan. The upper right is two scans, merged. The lower left is three scans merged, and the lower right is four scans, merged.
If I was going to do this myself, I would try Will's advice and do four scans, one with the negative rotated 90 degrees each time, to change how the scanner light hit the dots on the negative. The above examples are (as far as I can tell) just moving the slide on the scanner bed. Rotating it might get a better result, in theory.
This would increase dynamic range. But not resolution.
Multiple scanning of images, with exact registration, only works because it eliminates noise by averaging out the pixel information. In a perfect world, with zero noise introduced in the scanning stage. multiple scanning would have no effect.
There is some software for this with digital capture (should work with scans too i think), but I don't remember the name of it. Anyone?
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"
Yes I agree. I edited my post to make that more clear.
The main one is PhotoAcute ( http://www.photoacute.com/ ) which is available for windows and mac. It looks very fully featured, but is $150 for the full version. There is a free trial version as well.
Also found that Deep Sky Stacker can do it, using the NASA Drizzle algorithm (yes that's what it's called): http://deepskystacker.free.fr/english/index.html Deep Sky Stacker is free. Looks complicated though. It is windows only.
Also found Chasys Draw IES can do it, as described here: http://www.jpchacha.com/chasysdraw/h...stack_sres.htm It is also free and can be downloaded here: http://www.jpchacha.com/chasysdraw/index.php It is windows only. It looks a little easier to use, and more for the intended purpose, than Deep Sky Stacker.
Finally, you can do it in Photoshop with this tutorial, only published a few days ago: http://petapixel.com/2015/02/21/a-pr...ith-photoshop/
Last edited by fishbulb; 2-Mar-2015 at 11:57.
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