Film Scanners: Bogus dpi specs?

[Fernando2]

Heres a review of the Epson V700 that i wanted to get (skip to the image quality paragraph). It states that the actual dpi the scanner was able to reach was 2300dpi, compared to the 6400 dpi that is indicated by the manufacturer.

Whats your take on this? And while we at it, i do need a affordable scanner 😀

Hello papo,

the question of claimed vs. actual resolution is really complicated, unfortunately.

I've written a review of the V700/750 some time ago (in italian, but I hope illustrations and measurements may be of help) http://www.effeunoequattro.net/htdocs/freecontent/FC_ProvaV700/index.php

To summarize: yes, expecially for consumer flatbed scanners, manifacturers like to publish "theoretical maximum sampling frequency", not resolving power.
And while it's generally good to have some headroom for sampling frequency (sensor resolution) vs. scanner lens resolving power, in most cases the difference is enormous. 🙁

As others said, the weak link is the scanner lens (and anyway, those flatbeds use staggered sensor arrays instead of true 6400ppi-capable linear sensors).

The V700/750/800/850, with very careful technique and 3rd-party holders (which grant much finer focus adjustment) are able to (barely) resolve about 40-45 x 60 line pairs/mm, when scanning at 6400ppi. That may translate to 2100x3000 "real" ppi.

If you shoot 120 film, that may be enough for quite large prints, with proper sharpening.
For 35mm, well, a dedicated filmscanner (Reflecta, Pacific Image etc. if buying new) would do quite better.

Fernando

 

[Steve M.]

If the scanner manufacturer is interpolating the specs then they most certainly are bogus. You cannot create pixels out of nothing, and that is what interpolated pixels are....nothing.

Digital camera makers do exactly the same thing when they give the dynamic and tonal range specs on their sensors. Yes, many are better in that regard than film if you just look at the numbers, but the specs are an illusion because what the specs won't tell you is that at the high end the photos will be blown out, and the low range will be muddy in the shadows.

Dynamic range usually relates to RAW files, but you cannot get the same tonal range as RAW once you save to a TIFF or jpeg file. No digital camera that I know of can come close to the tonal range of film (assuming we are talking about a slow film and it's correctly exposed). W/ film, what you see on the neg is what you get. It's a useable tonal range and it correlates very well w/ what we see because it IS what we see. It's light on film. Digital data is just that, data composed of ones and zeros, not optical, and has a pie in the sky tonal range. A digital sensor is not a negative, and does not record light the same way. All of which is why no matter how good the scanner is, a properly made darkroom print is the better way to go. But if someone is digitizing a neg which will simply be viewed on a computer monitor composed of pixels, it's all moot at that point. I have some photos made from scanned negs, and w/ a lot of time in the editing process they look great. But they don't have the detail, tonal range and "look" of my darkroom prints on fiber paper. Apples and oranges.