Minimum dpi for good prints?

[burtharrris]

Hi everybody, I'm going to start scanning some of my film, and I was wondering what the minimum dpi would be to have quality prints. I plan on doing 8x10s from my Velvia and E100G slides, and T-Max and Tri-X negatives. I'm not printing fine-art quality, but I believe I have a somewhat discerning eye. I understand I'm limited by my printer resolution, but if you had to pick a number (e.g., 300 dpi, 600 dpi), what would you recommend?

 

[Hair Bear]

What are you scanning on? and is that 300 or 600 at 1:1 with the slide or with the enlargement?

Some scanner have better or true resolution than others. Not all scanners at 600dpi are the same. Some are making up the information (interpolation), some are better than others at doing this. I have had pro scans done at a hi res and not so hi res and the later was the better image.

best rule of thumb would be scan at the max res your system can handle and your printer can show.

Do a couple of test scans at say 300 and 600 of the same slide and print them and compare. If your eye tells you the 300 is OK then there is your answer.

 

[Don Simon]

I would have thought a 300 dpi scan of a 35mm slide would produce a fairly small image. For 35mm slides and negatives which I scan and print at up to 8x10, I scan at 3200dpi (or 2400 with medium format film).

 

[burtharrris]

Hair Bear, I never actually think to just try a few different things and figure it out myself, haha. I always come on here and try to find a real answer first .

I apologize, I should have been more specific. I used a Nikon Coolscan at the art labs at school (penn state), and they scanned my slides in at 4000dpi (1" x 1.5" X 4000 dpi = 4000x6000 pixels).

My real question was, assuming I had an image file that was 8x10 inches, what kind of resolution do you think I'd need.

 

[Hair Bear]

Hair Bear, I never actually think to just try a few different things and figure it out myself, haha. I always come on here and try to find a real answer first .

I think thats what forums are for, but it can be hard sometimes to give an answer with out asking a load more questions. Ultimately only you can decide what res will match both your eye and printer quality and hence why I suggested what i did

Also you asked about 300 or 600dpi and not 4000dpi! ZaphodB is spot on, enlarging a 300dpi slide scan to A4 just isn't going to work.

4000dpi should be Ok for that sort of enlargement. In general I find 300 dpi at 1:1 size is about right for most things uncluding commercial 4 colour printing, thats where I start.

 

[Don Simon]

I'm now very confused indeed. You say "assuming I had an image file that was 8x10 inches", and that you used a scanner, so are you saying that you have already scanned the slides, and now want to print them?

If you're asking at what resolution to scan the slides, I would still say around 3200dpi. If you already have the slides scanned and now want to print the images, I would say 300dpi is fine. Of course you will have to resize the images to 8x10" if you have not done so already.

 

[burtharrris]

Alright alright. All my questions were answered, thank you both. Just for clarification:

1) I scan slides at 4000dpi, that was a bit of a useless statement, not related to my questions.

2) True, 300 dpi slide scan would only be 300x450 pixels.

3) I was asking about a print image that was 8"x10" (1:1 print ratio) what dpi should be used, which was 300dpi.

Thank you guys.