> Was this long epistle supposed to make me read for a sufficiently long
> period of time to forget that you didn't actually answer my question
> about 5 pass sharpening? It's a good thing you're not a talking head
> else I'd think you were deliberately avoiding it. :-)
LOL, ya think?
> But I agree with your assessment of 10-12 MP max resolution for a 35mm
> film scan. That's roughly equivalent to 60 lines/mm which is about as
> good as you can get from tripod based photos in the field regardless of
> film and lens resolution. Provia 100F is capable of more than that but
> the camera would probably have to be mounted on a steam engine... inside
> your studio. And we know OMs very much need that unless the mirror and
> aperture are pre-fired.
Provia's numbers are not overly even across the spectrum or contrast
level. If you look at the 70% numbers, you'll see that Provia is down
quite a bit. Velvia 100 (not F) easily trumps it and is arguably
better than Velvia 50. Still no where near Kodachrome 25 which had
that natural in-film USM going on. Where digital has a massive
advantage over film is that when comparing usable resolution, it
remains the same at any contrast level. Digital is definitely not even
when it comes to resolution across the visible light spectrum, but for
most images it does hold an advantage. Anyway, this is one reason why
I've always had kittens about comparing to Provia. It's a decent film,
but definitely not the resolution leader.
> How about illustrating exactly what you're talking about here. Can we
> see a small 1:1 pixel crop of a single scan and then the same from your
> multi-pass, multi-sharpened image. I'd like to actually see the
> difference in detail.
Sure. I'll do a workup on this. I provided Brian with a couple of 100%
crops of the image in question, but due to other circumstances, this
ended up not being the best possible image to use for the example.
Besides, I screwed up on it. :)
With this image, you can make out the branches of the trees 1500
meters away. In otherwords, you can make out approximately 0.1m
objects 1500 meters away on a 4000 dpi scan of a 35mm slide taken with
a 35mm lens. I'm no good with math, so I'll leave that to you guys.
A nifty NASA imaging trick is to take the image and superimpose it on
a grid at an angle. This grid has multiple pixels per pixel. By
spreading out the pixel data at an angle, we end up being able to
break up the pixelization. Once the pixelization is broken up, by
combining that aspect with a whole lot more pixels we can then apply
sharpening algorithms to the image to get details which are not
visible in the original image. I've experimented with this and have
found that it works, but is very processor intensive.
AG
--
Ken Norton
ken@xxxxxxxxxxx
http://www.zone-10.com
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