HP-5370C vs. PhotoCD

By Ian Gorman

I have done some more tests and found a way to get a fairly good idea of how well the HP-5370C scanner does.

For scanning right on the glass, resolution is 1200 DPI. If I happen to get a gray/black edge between two pixels, I get almost the full brightness change from one pixel to the other. Otherwise, the change occurs over three pixels, with the middle pixel having an intermediate value. I scan prints and sheet negatives right on the glass, and get the maximum resolution. I get almost the same detail as a Photo CD scan at 1536 x 1024. I think the difference is mostly due to Kodak using more powerful software. Red, green and blue images are not completely in register, the edges differ by one pixel in some places.

If I put 35 mm slides and negatives in the holders suppplied by HP, the film is (in both cases) 1.5 mm above the glass. Resolution seems to drop off to 600 DPI or less, and I cannot get a sharp edge to split between two pixels.

This is an HP-5370C scan from the scale of a vernier caliper. The lines next to the large "7" are approximately 0.3 mm above the glass, and the lines next to the large "6" are about 0.5 mm above the glass. The lines are about 4 pixels wide.

I think we can safely say that a scan of a 4 x 5 negative or slide at 1200 DPI will be at least as good (for detail, not for colour) as a 3072 x 2048 Kodak scan of a 35 mm negative or slide, and might get close to the next higher resolution in 35 mm. A scan of 35 mm on the glass will get close to a 1536 x 1024 Kodak scan, but scans using the HP holders will not even be as good as the 768 x 512 Kodak scans. The HP-5370 is a pretty good scanner for 4 x 5 when you are on a budget, but you have to be on a very tight budget to use it for 35 mm. For me, the 35 mm performance is a bonus, because I did not expect even the results I can get.

One more sample -- my Dad photographed a lot of papers after the war (no xerox in 1946!). I think the typewriter was 6 LPI, 10 CPI. An 8.5 x 11 page fills the 35 mm frame at this magnification.

The attachment was on 35 mm negative, scanned close to the glass. Scanning in the slide holder provided by HP gives a less sharp result.

The negative is noticeably sharper than the scan, so a film scanner would give better results because of the higher resolution.