Measured scanner resolutions

Started Jan 16, 2021 | Discussions thread
Sasquatchian Regular Member • Posts: 175
Re: interesting comparison !

Overrank wrote:

Sasquatchian wrote:

This entire thread seems to echo what we all discovered 25 years ago when comparing scanners toward the end of the 90's.

That was basically that all of the CCD type scanners, no matter what their claims were, produced somewhere in the range of 2700-3200 real world dpi, no matter how many pixels they were asked to produce. That included the original Imacon CCD scanners as well.

I don't know how you measured the resolution but (and some personal work) rate a reasonable number of consumer scanners at around 4,000 ppi in real world tests (USAF 1951 targets) - Coolscans, Reflecta/Primefilm, Minolta.

I'm no longer convinced that MTF charts tell you anything useful for real world scanner resolution. Instead they appear to be a function of the the underlying lens response (which is often higher).

Let me be clear. I did not measure but was seeing the results of the tests that Aztek was running back around the turn of the century. That's also how I discovered the whole software bug in Trident regarding the auto aperture setting - y'know  - when two identical scanners, one an Aztek 8000 and one a Howtek 8000 produced hugely different results at 8000 dpi. The only difference was the software. The Aztek was hitting, like I said, around 7200-7400 dpi while the Howtek was maybe a bit over 5000. When I finally understood what was going, I realized that whoever did the Howtek scans did not know the software well enough to use it correctly for that test.

In the interim, I've been hired many many times to rescan film that had been previously scanned on scanners ranging from Nikon, Imacon, Hell and, notably, Crossfield, with a piece of film for the L.A. Natural History Museum, scanned at 8000 on that British behemoth.

I re-scanned some film for now deceased fine art photographer Tom Millea before he died. He had scanned it at 4000 on a Coolscan. Sent me the film and his scan. I scanned on the Howtek at 4000. Same number of pixels but the same amount of information. You'd have thought it was a different piece of film. The drum was that much better. That Crossfield scan I re-did for the museum was just crap. It wasn't sharp. The detail seemed to be missing. The grain was mush, and you could see where the whole thing jumped, putting part of the scan a few pixels offset from the rest. Ugh. The museum was ecstatic. Me, I was just surprised that the  $120K scanner was so bad. Was it the hardware,  the operator, or both. Who knows. I've also re-scanned  quite a number of images that  were originally scanned on a Hell 3300, which claims 11,000  dpi or something crazy like that, but it turns out that that only has a 10 micron aperture so it's physically limited to 2540, but in reality gets more like 5000 in one direction and 2500 in the other.

The  bottom line is that I don't really need to know eactly what my scanner does. I only need to know that it does the job.

I did go to the website you mentioned and didn't  find it very helpful, but it did seem to use the manufacturers claims for density capabilities rather than measure their own. Those numbers are notoriously inflated or have so much noise at the claimed spec that they're unusable. There are a lot of things to consider when thinking about getting good scans and  sheer resolution is only only one of many factors. Remember all those advertising claims from Imacon - "virtual" drum scanner. 4 point whatever density range. They never told you that the images weren't as sharp or as dynamic as claimed, but more importantly they never told you about the flare that their internal lens produced in high contrast areas of your film. Another ugh, as in ugly.

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