Scanner DPI Options

[Ken Lee]

The standard resolution for printed magazines is a 150 line screen, IE 300 dpi.

As Nathan points out, high contrast detail works better, but on average the Epson gets somewhere around 2100 to 2300 spi.

Therefore you can enlarge by a factor of around 7x or 8x at most, and still get 300 dpi.

If some of your negatives contain only 30 lp/mm, then you ought to try this before purchasing the scanner: You may not be delighted with the results, even with a perfect scanner. They may not be up to the standards of Large Format photography. Find out for yourself.

[Bart B]

Found this site:

http://www.largeformatphotography.info/scan-comparison/

Decent comparisons, I think, to compare different scanners using the same negative.

[Ivan J. Eberle]

Ken, the standard for high speed web printing screens (magazines) is 133 dpi. For better quality presses it is 150 and sometimes 200 dpi, rarely higher with the possible exception of fine art repro in books

[Bart B]

When I did some technical documents working at Hewlett-Packard, the graphics group standard for printing marketing photos in brochures and such was 300 dpi. As explained to me, that's based on the human eye being able to resolve no finer than 6 line pairs per millimeter at a viewing distance of about 12 inches. So, 12 lines/dots per mm equals about 300 dpi. A large print (4 x 5 feet) viewed at 6 feet could have 50 dpi and look very sharp to most of us.

Of course, there's contrast and other issues at hand. Checking around the web for this info showed numbers from 180 up through 360 dpi. As long as the dpi value gives a reasonably sharp image for the viewer as seen from his viewing distance, all kinds of numbers will emerge.

[Bart B]

Well, my next phase of scanning 4x5 B&W negatives is using the Epson 3200 I just bought; that is, as soon as it arrives in a box.

It doesn't have the SilverFast software CD, but I'm wondering if it's really needed for scanning B&W negatives. Some web sites say it's not needed as Epson's software does a good job for B&W negs. Yet, a few say SilverFast's needed even for grayscale negs.

I'll post process scanned files with Photoshop Elements 8.

And SilverFast's web sites list several versions available for Epson's 3200.

[Ken Lee]

Ken, the standard for high speed web printing screens (magazines) is 133 dpi. For better quality presses it is 150 and sometimes 200 dpi, rarely higher with the possible exception of fine art repro in books

From what I can tell, lpi and dpi are not interchangeable. LPI appears to be equivalent to line pairs per inch, which is double the number of dots per inch or dpi, IE double the number of pixels per inch or ppi.

According to this discussion of standard line screens on PrintPlanet which describes itself as "the world's largest e-community for print":

"For 150 lpi you need your pictures to be saved in 300 ppi."

Some of the contributors mention that on high-quality stock, they use screens of even higher resolution. On poorer stock, they user lower resolution, naturally.

According to another member (emphasis mine): "Of course, 300 dpi is what we recommend, but just saying the least dpi we can get away with without seeing the "stair-step"."

I have corrected my original post to read "150 lpi screen, IE 300 dpi".

[rdenney]

When I did some technical documents working at Hewlett-Packard, the graphics group standard for printing marketing photos in brochures and such was 300 dpi. As explained to me, that's based on the human eye being able to resolve no finer than 6 line pairs per millimeter at a viewing distance of about 12 inches.

The standard sounds right, but HP really printed brochures using a 300-line process color screen? Color me doubtful--the ink spread would turn that into a mess using web offset.

I think you mean they required photos at 300 pixels/inch for reproduction. That is not uncommon as the starting point for 133-line magazine process color.

Or maybe they were printing production marketing stuff on high-production laser printers rather than using process color lithography. HP lasers have always been based on multiples of 300 dpi.

Rick "who always provided 300 ppi files to magazines" Denney

[Ivan J. Eberle]

No, you were talking about resolution at line screen for magazines, Ken; lpi is the term in the traditional ink printing industry. Where you may be confused is that it was generally considered necessary to oversample when scanning by a factor of 2X from film, so film was scanned at 266 dpi (that is, at the final repro size in print) or greater for a 133 lpi screen. 300 dpi scan at the printed size dimensions would be specified if 150 lpi screens were used. Of course in CMYK color print processes the dots were overlaid in a rosette pattern and screened at various angles to prevent moire so looking at it under a microscope there'd be more than 133 dpi total in the final printed page-- but 133 lpi was the resolution of the half-tone screens used in the vast majority of web printer processes.

[Ken Lee]

Excellent - Thank you for the helpful explanation.

[Kirk Gittings]

I think Sandy King did some actual resolution tests posted in some thread here not too long ago where he found the 750 to deliver 1600 if I remember correctly. That agrees with my tests too. The 4990, 4870, 3200 will all incrementally go downhill from there. I've owned all of them and used them extensively wet, dry, upside down-you name it. With 4x5 i won't use one for prints over 11x14. Just my personal opinion.....