Scanning Resolution

[robertrose]

There are several threads related to specific scanners; here I just wanted to suggest that worry about super-high resolutions such as 6400 dpi for 4x5 film is overkill, and will result in many unhappy hours at the computer.

For example, suppose that you are going to print a 16x20 print on the popular Epson 3800 or 3880. You want at the most 360 dpi for the output file. This means a 5760x7200 image for a 360 dpi print. To get that from a 4x5 negative you only need 1440 dpi. Even at that lower resolution you will downsample for web size images, or if the subject matter requires (see http://robertrose.photos/galleries/l...iver-2008.html).

There are many other issues if you are printing, such as whether to use 8-bit or 16-bit files, etc., and I refer you to Eric Chan's excellent website http://people.csail.mit.edu/ericchan/

There is an excellent set of articles about scanners at the LF home page, but in all honesty I have yet to see a single person examine my prints with a magnifying glass. It is subject matter and composition that makes the photo.

[Peter De Smidt]

<snip>
For example, suppose that you are going to print a 16x20 print on the popular Epson 3800 or 3880. You want at the most 360 dpi for the output file. <snip>

What is your evidence for this?

[Jim Jones]

Scanning at exactly the right dpi to print the largest print I expect to make seems logical, but scanning at higher resolution and carefully editing that file allows for perhaps future printing at even larger sizes. I agree with Robert that any downsizing and final editing should be done in the computer at the printer's native resolution. It works for me.

[Preston]

Scanning at exactly the right dpi to print the largest print I expect to make seems logical, but scanning at higher resolution and carefully editing that file allows for perhaps future printing at even larger sizes.

Indeed, it does seem logical, and would certainly work well for a person who does not have a computer with the horsepower and/or storage for huge files. Personally, I scan at 1800 ppi (the max for my Microtek 1800f and Vuescan) to produce a 16 bit TIF file. This file is then saved as a PSD 'master file'. All my editing is done on this file. Output files are for printing or the Web.

I agree with Robert that any downsizing and final editing should be done in the computer at the printer's native resolution.

Same here. If I need to make small adjustments to a print file or Web file, I do exactly as Robert and Jim suggest. Works for me, too.

--P

[vinny]

So..........if i want to make a 16x20 I should scan my film at 1440dpi, open the file in photoshop, spend a considerable amount of time removing dust, make any adjustments, then finally print it.
Then when I get an order for a 32x40, I should fire up the drum scanner, remount the film, and do it all over again?
Thanks for the suggestion but, NO THANKS.

[Bill Burk]

Don't you work on a managable proxy file, save the actions and original hi-res, then anytime you get an order... downscale copy of original to optimum for target output print and then apply the saved actions to it?

[Peter De Smidt]

I was under the impression that the native resolution of some Epson printers, with "finest detail" checked, is 720 dpi.

See Eric Chan's comments on print quality at: http://people.csail.mit.edu/ericchan...tml#native_res

[paulr]

"Finest detail" is a raster setting optimized for line art; it's not ideal for images with photographic gradients.

There are other setting that give 720ppi that are appropriate for photographs. They're only available with gloss paper presets.

I'd recommend doing a blind test (blind as in, you don't know which is which), preferably with three prints of an identical image. In my experience it's usually impossible for anyone to tell the difference between 360 and 720ppi. The only exceptions I've encountered have been with crisp diagonal lines that are just a bit off from vertical or horizontal. Sometimes at 360ppi you'll see some slight aliasing (jaggedness of the line).

I don't believe with a photographic image, anyone will see more detail or subjective sharpness at 720ppi, all else being equal. When I was printing a body of black and white work from 4x5 scans using piezography, I did it at 720, because it felt badass. But I didn't have a rational reason to do so.

[djdister]

This is a losing argument. Been there, done that. Optimum scanning resolution should be maximized for whatever you intend to do with the final image file. Its as simple as that.

[paulr]

My approach to scanning has been to run tests to find the highest resolution that makes a visible difference. With my old 4870, with shims and a wet-mount setup, I could see the difference between 2000ppi and 1800 (barely). I could not see the difference between 3600 and 2400.

I settled on scanning at 2400, because it divides evenly from the scanner's sampling frequency, and allows plenty of downsampling to help control noise.

Years ago I would immediately downsample to print resolution, since drive space was precious and the computer sluggish. I also often worked on a half-resolution proxy file. but today I'd probably work on a full-resolution master file and then make size-specific versions for printing.

Some people use a program like Vuescan and just save the raw scan file. It's big, but it grabs every bit of information the scanner produces (resolution, gradient, infra-red noise channel, etc..) so you can go back to this file and reprocess at any time you like.