How many DPI should I scan film at?

BetterSense · 08-08-2008, 01:20 PM

I recently discovered that one of the computer labs in the school library has Epson flatbed scanners with a photo scanner thing in the lid.

So this means I can get film developed to negatives only, thus saving a bunch of mone...I mean letting me shoot a lot more.

Anyway, I scanned my first batch at 1200 dpi. But I think the 600dpi scans I made of Walgreens 4x6 prints have better detail, despite the prints being much darker than how the film scans turned out.

I think the film scanner goes up to 6000dpi but 1200dpi was already slow. In the attachment, the 'base' image is the film scan, and the 'patches' at the bottom, middle-top-right and upper-left are pasted in from the print-scan. The print-scan had to be lightened substantially.

In the second, the left side is the print-scan, the right side is film-scan, with no PP.

Entropy · 08-08-2008, 01:32 PM

The higher the better until you see diminishing returns.

1200 dpi scanning 35mm film is effectively less than scanning a 4x6 at 600, if you compare the number of dots per image height (dpi * physical height)

Also, photo labs often perform some basic color/exposure correction automatically during the print process, so expect to need to do that for film. I strongly consider obtaining a color calibration target that matches your film (Google search "Wolf Faust") and profile your scanner.

Also, what model Epson flatbed is it? Some of them have a great rep, some are utter crap. For example, the marketing for the scanner included with the RX595 all-in-one printer/scanner outright lies - it claims 48 bit color but it only does 24 bit color, I've never seen an option for more than 8 bits/channel (24 bpp) in any software, Windows or Linux. For this reason I probably won't be buying any Epson products again - In addition to their Linux support being awful compared to what it used to be (drivers used to be fully open source but now have binary-only components), at least some models in their product range do not perform as specified. I realize the RX595 is low-end, but if it says it does 48 bpp, it should do 48 bpp!

BetterSense · 08-08-2008, 01:38 PM

I'm not positive on the model, except my fuzzy memory says it's a 24xx. It's a flatbed scanner with a little flip-out door in the top. You have to take out the white mat in the lid in order to use the film function. The 'Epson Scan' software on the lab computer allows options for 24 and 48 bit color, I used 24.

My scanner than I scanned the prints with is a Canon pixma mp210 that I had a great afternoon with getting to work with Xsane in Ubuntu 8.04.

Note, that I only PP'd the print scans, cause I felt they were too dark. I was saying to myself when I got them that maybe I should have been using the Exposure Compensation dial on my Program Plus.

emalvick · 08-08-2008, 01:47 PM

If you compare the resolution of the final images, you'll see that a 35 mm negative at 1200 dpi is much coarser than a 4 x 6 at 600 dpi...

e.g. Neg @ 1200 = 1700 x 1134 pixels = 2 MP (approx)
4 x 6 @ 600 = 3600 x 2400 pixels = 8.6 MP (approx)

You'd have to go to 2400 dpi to start getting close to the 4 x 6.

As for the quality of the scans, that is highly dependent on the scanner. I've done film and slide scans with various scanners and some of the cheaper ones don't back light things sufficiently to make a nice bright scan. I have found that better scanners and scanner software do allow you to adjust the brightness and result a bit better. An expensive scanner I once used did a great job (dedicated negative and slide scanner).

In terms of speed, I think what happens on some of those flatbed scanners is that they don't truly reach the resolutions they say they do but rather do multiple scans to create an apparent resolution. I'm not an expert with scanners, but my old flatbed reported that it could output 3600 dpi but in reality the optics were limited to 1200 dpi, so as soon as I went over that threshold the time to scan really went up (i.e. it made multiple scans and interpolated to get the resolution requested).

*graphicgr8s* · 08-30-2008, 10:48 PM

Set the scanner to 300DPI. Set the scaling to the size you eventually want to print at. Like 8 x 10 at 300 DPI. It'll print fine.

*gpaual* · 08-31-2008, 04:08 AM

Getting Started Scanning - Printing Digital Photos and Scans

there's a lot of info out there on this topic....good luck.

*gpaual* · 08-31-2008, 04:43 AM

i am posting an old chart from my course at nyip some years ago....hope you find it useful.....