Scanning Resolution Question

[mjs1973]

I have contacted a couple local photo shops about scanning some slides for me. They both said they can scan them at a resolution of 2000x3000. My question is, how large of a print will that resolution make before the image starts to loose quality? One guy said he would feel comfortable making a 12x18" print from this size scan. Is that about what I should expect?

Thanks in advance for any info you can provide.

[another view]

The "standard" rule has always been 300dpi - in this case, that would work out to 6-2/3" x 10". But 300dpi is pretty conservative. Experiment a little and you'll see that prints tend to smooth out some of the problems. It's hard to explain but easy to see. It may be hard to see a difference at 240dpi (which would work out to 8x12. You can probably even go down to 200dpi and be OK (this is 10x15).

Short answer - 12x18 would be a "maybe", 8x12 no problem. It can depend a lot on the shot too - as far as subject matter, amount of detail in the shot, and especially your own assessment of what's good and what isn't.

Recently I emailed a quick shot to a friend. He liked it enough to print it just as the file was set up. I didn't really pay attention to how I sized it, just making sure it was 800 pixels on the long side so it wouldn't be a huge file going thru email. I figured out later I left the default 72dpi on the file in Photoshop, so when they hit "print" they got a shot that almost filled the 8.5 x 11 piece of paper at 72dpi. It really didn't look bad at all until you got really close and in good light - then you could see it falling apart a little. But I was surprised how good it did look.

[Outdoorsman]

The longer answer:

I think the answer here depends on your desired output size. How large do you want the image to be? And how large is feasible with your chosen film? I would be comfortable enlarging Velvia 50 and Provia 100F to 20x30, and I also had a slide of Provia 400F enlarged to 20x30, with acceptable results. And how large a file are you willing to play with on the 'puter? You can scan any slide at any resolution (equipment willing) but if you won't need something to make a poster out of, then a lower file size might be better.

Have them give you a test of a few different resolutions, 150, 300, 600, maybe even 1200 or something, to see what works best with your film and their equipment. I had a local guy tell me he didn't need to scan a slide at my desired 2000 dpi resolution; saying 300 would be enough. I didn't quite get it, but I guessed he meant the output size would be a xx" by xx" at 300 dpi-- he was not considering the file size, rather, the printed result.
I would say to give them your preferred output size at desired print resolution, and leave the rest to them. That's what I do, anyway... I say, "Make this slide an 11"x14" at 600 dpi" and that's what I get on the disc.

I also agree with AV; you can print at surprisingly low resolutions and still get an acceptable print. The same thing happened to me where I had promised to make a one-month calendar with an image of mine for my boss, but I picked a web-sized version of the file in haste. It printed just fine, though sized to 5"x7" at 72 dpi... as long as the customer's happy, eh?

At the shop I worked at we had an Epson 9600, which could print at very high resolution, yet we rarely did anything over 300 or 600. And no one ever knew the difference, sometimes even us...