On 6/12/2012 7:54 AM, Ken Norton wrote:
>> Care to describe your "5 pass sharpening process"?
> The act of scanning is actually that of taking a picture of a piece of
> polyester that happens to have some form of image on it. The scanner
> is a digital camera with a lens.
>
> In a single pass scan, this is a single picture. The problem we run
> into with single pass scans is aliasing artifacts where grain (or dye
> clouds) are sampled in a such a way that we are likely to get wild
> swings in the values of each pixel. So, for the highest level of
> quality we overscan. Each time the scanner photographs the image,
> there is a very tiny offset as the stepping motors don't quite get
> things exactly aligned. With this multi-pass scan, we effectively
> increase the diameter of the sampled area for each pixel. This reduces
> the grain aliasing.
>
> Unfortunately, overscanning like this tends to reduce sharpness. I
> have found that there is no specific setting you can use to bring the
> image back to maximum sharpness. For one thing, this is so film
> dependant (and scanner dependant),
I've done far less of this than have you. Using the FS4000 on Portra (160, I
think), multiple passes definitely
increased the amount of fine detail. I seem to recall 7 as the magic number of
passes for this particular film/scanner
combo. I also ran into a roll of older slide film where additional passes made
no improvement at all. Whether film or
lens, I couldn't tell.
> that the settings which work for
> the original Provia 100 won't work for Provia 100F. Velvia 50, 100 and
> 100F all scan differently too. Let's not even talk about print films.
Let's. Oh, I just did. Worked for me.
> So, overscanning reduces sharpness. OK. But does that mean that the
> information is gone? Of course not.
Again, not much of this effect in my limited testing. It was apparent right out
of the scanner that there was more
detail. Sharpening did, of course, improve on that. This was before I was using
Focusmagic. I'll bet it would do a
better job.
> <big snip>
> When do I use multi-pass overscanning? Not for every shot. In fact, I
> usually only use it for something that I know will end up printed big
> or when there is so much dynamic range which needs to be protected or
> recovered. The churn and burn stuff is usually single-pass. The latest
> versions of Kodak Portra do just fine with single-pass. Slides with
> extreme dynamic range, such as "Sunburst Lake", need a lot more work.
> A LOT more work.
>
> The point of this epistle, is that with a creative and disciplined
> approach to scanning technique and image recovery, there is a whole
> lot more detail buried in these old film images than what we generally
> give the technology credit for.
Depending on lens and film, yes that can be true.
> <another big snip>
Grainless Moose
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What if the Hokey Pokey *IS* what it's all about?
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