You might find this article helpful, particularly the part about resolution: http://www.kennethleegallery.com/htm...ning/index.php
First, let me say drum scanners are not perfect by any means. Quite exposed to the mechanics of the system.
On the other hand, they capture the info from the emulsion in a different way compared to the CCD based scanner, not relaying so heavily and widely in the lens. But optical resolution is not the only issue. Flare in the CCD based scanners also impacts the color purity.
As other members mentioned, IMHO the resulting optical resolution of the epsons is subtantially lower than 6400 dpi.
Yes, the various tests out there measure the actual resolution of the Epson lineup (4990, 700/750, 800/850) at around 2000-2400 dpi depending on the model, the test, etc.
A drum scanner (properly set up, trained operator etc.) can deliver far more realized dpi, as well as better color rendition etc.
-Adam
If we print at 300 dpi and have Epson scan with 1800 dpi minimal isn't that a possible 6x enlargement?
Which is 48x60" and bigger than most anybody prints.
Of course Drum is better, but is it worth it for amateur work, especially considering how cheap inkjet prints can be when done in quantity?
And what happened to fractal extrapolation?
If you want to print 8x10ft at 254 ppi, you are looking at about a 24380 x 30480 pixel image, or 743 megapixels. To get that kind of actual resolution you'd need to be scanning an 8x10 sheet of film at over 4000 real dpi, and under ideal conditions (both photographic and scanning). No matter how high the dpi of your scanner, or the fineness of your film grain, you are never going to get that kind of resolution out of 4x5, and it would be a challenge for 8x10 too.
Realistically the available resolution from film depends on a ton of factors - type of film, aperture used, lens type, any motion blur, film flatness etc. - not to mention the quality and type of the scan. For example, you can get significant resolution improvements with a flatbed by using a calibrated film holder, or significant resolution losses with a drum scanner if it isn't focused correctly.
With ideal conditions and a good drum scanner, you can get 320+ megapixels of real resolution out of 4x5. This would be fine-grained black and white film, like Delta 100, a larger aperture (f/11 to f/16), and a drum scanner at 4000+ dpi. The same image, scanned with an Epson flatbed, you should be able to get about 100 megapixels of real resolution out of it (320/(4000/2400*2))=96
Under less ideal resolution conditions - color film and a smaller aperture (f/32-ish) - you're looking at more like 100 megapixels with a 4000dpi drum scanner, and correspondingly less with a flatbed. Aperture and film choice have a HUGE impact on available resolution for a scan, I can't stress that enough. (f/64 is all well and good, but if you're trying to maximize resolution, the diffraction is going to kill it for you)
See the tables on this page for the details on those resolution numbers and how they were tested. (I'm not just making up numbers here. )
-Adam
Last edited by onnect17; 11-Feb-2016 at 18:30.
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