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Relationship of scan size (MB) vs print size

Ted Adamczyk , Jan 30, 2007; 05:47 p.m.

What is the basic relationship between scan size and print size? For example, 100 MB generally produces a good 16" x 20" print. Will going to 200 MB be worth the additional effort/cost? How about prints sized greater than this, e.g., 18" x 24", 20" x 24", 30" x 40"? Appreciate knowing what you have found from experience?

Responses

George Otigbah , Jan 30, 2007; 05:51 p.m.

Ted Adamczyk , Jan 30, 2007; 06:08 p.m.

Thanks George. This is what I was searching for.

Marshall Goff , Jan 30, 2007; 07:14 p.m.

That assumes 8-bit scans. Double it if you scan to 16-bit files.

John Kelly , Jan 30, 2007; 07:28 p.m.

1) 4000ppi produces about 125MB files from 35mm (Nikon and Minolta scanners)..over twice what Alpenglow asserts. Both Nikon and Minolta seem credible standards, and in my experience they produce identical detail resolution at 4000ppi. I've not printed above 12X18, but 4000ppi scans from 35 can be exquisite at that size.

2) Epsons default to 720dpi and look significantly better at 1440dpi in my experience, at least on letter size and above. 300dpi is noticably inferior, even at 5X7. Epsons are presumably standards for printer quality, since they're used by so many serious photographers.

Sounds like Alpenglow is using a minilab system of some sort, like Costco or Walmart.

Marshall Goff , Jan 30, 2007; 09:38 p.m.

John, I think there may be some confusion there. The dpi number in Epson's print driver isn't necessarily related to the dpi number in the file (more correctly called "ppi"). The 300ppi number on alpenglow's page is fine, even if the printer is set to 1440dpi or even 2880dpi. Essentially, the 1440dpi is counting the number of dots laid down in a dither pattern to create the equivalent of each pixel of actual color in the image file itself.

John Kelly , Jan 30, 2007; 11:47 p.m.

Aspenglow wants us to believe that there are print size "limits" to 4000ppi scans of 35mm: There are no such limits unless one is hostile to 35mm film in the first place, can't stand grain, or may be hostile to interpolation (which can be beautiful in itself, like Arabic mosaics).

I've seen gorgeous billboard-sized images scanned from 35mm, but I've never seen equivalently beautiful mural sized optical enlargements from 35mm. I think Aspenglow's mumbo-jumbo boils down to urban legend about size potentials.

Matt Neighbour - York, U.K. , Jan 31, 2007; 07:17 a.m.

Marshall - actually, for Epson inkjet printers, the print driver interpolates the file up to 720ppi. A quality improvement can be had if the file is interpolated to 720ppi before printing using a superior algorithm. QImage is superb for this.

I get great results using a Nikon Coolscan V scanning with Nikon Scan at 4000ppi and printing 13"x19" with an Epson 1290 at 1440dpi using QImage. The 8-bit file size is around 70MB for that, before QImage decides what interpolation is needed. Printing 12"x12" from Imacon scans of 6x6 film gives even better results.

It's nice to notice more and more detail the closer you get to a print.

Marshall Goff , Jan 31, 2007; 01:20 p.m.

John, I just took the Alpenglow chart as a starting point, or guideline, but I do think it could easily be read as stating limits, which is too bad. Personally, I think it's more misleading automatically to equate megapixels to scanned-image resolution - it may be mathematically correct, but there are some differences in the way the files behave.

Matt, I've seen some evidence (can't find the source) that the 1280/1290 actually interpolated to 360, but all the subsequent ones do seem to use 720. I'm impressed if you can really see a meaningful difference beyond 360 or so; I haven't been able to, either when dealing with scanned film (Nikon scanner, as well) or with digital capture (though there the file is sometimes being interpolated up already). [To be fair, it's been a while since I compared to the QImage interpolation, but the last time I did it didn't seem to offer a meaningful benefit over CS2 to me. Then again, I generally don't interpolate up all that much.] At any rate, I also print scanned film or digital captures at 1440 (now on a 2400, formerly on a 1280); I just don't interpolate them up beyond 300ppi for larger prints.

Robert Goldstein , Jan 31, 2007; 04:49 p.m.

How large can you go? It depends not only upon the resolution of the scan, but also upon the resolving power of lens, the ability of the film to capture detail, the graininess of the film, the subject matter, the shooting technique and the viewing distance. Thus, there can be no hard and fast rule.

With all of the above factors optimized, I have been able to make excellent prints at 14x21 inches from 5400ppi, 16bit scans of 35mm Astia.

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