Optimal Scanning Resolution

[widevista820]

Simple and to the point. I am having my 8”x20” negatives drum scanned to fine tune for Platinum Palladium printing. The files are tweaked in Photoshop then printed on Ultra Premium OHP Transparency Film. The drum scanner operator wanted to know what resolution to scan on. After some research and a few emails I determined that the 780 dpi setting on the drum scanner was ideal. He had initially suggested 1440 yet I think that is overkill. The negatives I am printing on the Epson are 8”x20”. So I would gather that 780 would be good as I am not enlarging. I did output one 8”x20” negative from the first scan and the sharpness and detail look fine. I will not really know until my Amergraph frame arrives in a week. Any one else out there drum scanning 8”x20” negatives?

-Bruce

[Bruce Watson]

You aren't making any enlargement, yes? So the print is the same size as the film. In that case, 780 spi should be fine. You could probably easily get away with something in the range of 300-360 spi, or 450-540 spi if you want to over sample a bit. You'd have to try them out and see what the final prints look like to know for sure.

As a drum scanner owner/operator I have to ask: Why do you want drum scanning for this application? I would have thought this a perfect application for a flatbed scan. Stitched if you need it. An Epson 7xx scanner could do this in two 8x10 pieces (three if you want a fair amount of overlap for stitching) and you could stitch them back together in Photoshop or some other application. I'm asking because it's expensive and I don't imagine you'll see much if any quality improvement since we're talking about a 1x enlargement here.

[Ben Syverson]

Fascinated by this analog -> digital -> analog "round trip." Will you post some pictures of the finished product when it's done?

[Don Hutton]

You aren't making any enlargement, yes? So the print is the same size as the film. In that case, 780 spi should be fine. You could probably easily get away with something in the range of 300-360 spi, or 450-540 spi if you want to over sample a bit. You'd have to try them out and see what the final prints look like to know for sure.

As a drum scanner owner/operator I have to ask: Why do you want drum scanning for this application? I would have thought this a perfect application for a flatbed scan. Stitched if you need it. An Epson 7xx scanner could do this in two 8x10 pieces (three if you want a fair amount of overlap for stitching) and you could stitch them back together in Photoshop or some other application. I'm asking because it's expensive and I don't imagine you'll see much if any quality improvement since we're talking about a 1x enlargement here.

Microcontrast of a drum scan will reveal all the nuances contained in the original - a consumer flatbed will lose some... It's not all just about resolution.

[PenGun]

Microcontrast of a drum scan will reveal all the nuances contained in the original - a consumer flatbed will lose some... It's not all just about resolution.

PMTs are nice but "all"?

[IanMazursky]

I always tell people to scan a little bit more then the current application requires.
Ive ran into this a number of times this month with a few clients. One wants an LVT 8x10 from a 100mb scan we did a while back.
I did tell them to scan for the future! You never know when you may have to repurpose it for a larger print or for archival purposes.

I would tell the operator to scan the film at the optical resolution (in relation to the aperture) to the spi you want. Depending on how sharp you want the grain, the aperture can be adjusted accordingly.
Im not sure which scanner they are using, maybe a hell 3000 series or a howtek 7500 (my vote and my favorite scanner next to the aztek premier).
The best results are usually obtained when youre not interpolating the scan by picking an arbitrary spi. Especially on smaller scan sizes when youre not near the far end of the scanners capabilities.

[Bruce Watson]

Microcontrast of a drum scan will reveal all the nuances contained in the original - a consumer flatbed will lose some... It's not all just about resolution.

For 780 spi you're talking an aperture in the range of, say, 32 microns. Such a scan is not likely going to recover all the information contained on the negative. In particular, it's going to leave some of the fine detail out of the scan file. This includes some of the microcontrast information. That's just the laws of physics.

Such a scan file will likely make a print that's nearly indistinguishable from a contact print at normal viewing distances. But you'll get very similar results from a flatbed scan -- nearly indistinguishable from a contact print at normal viewing distances, and nearly indistinguishable from a print from a drum scan, at normal viewing distances. Much depends on the operator, techniques used, etc.

[Lenny Eiger]

I always tell people to scan a little bit more then the current application requires.
I would tell the operator to scan the film at the optical resolution (in relation to the aperture) to the spi you want. Depending on how sharp you want the grain, the aperture can be adjusted accordingly.
Im not sure which scanner they are using, maybe a hell 3000 series or a howtek 7500 (my vote and my favorite scanner next to the aztek premier).
The best results are usually obtained when youre not interpolating the scan by picking an arbitrary spi.

Ian, I agree with you - it's always better to scan for not only printing but archiving as well.

However, my results don't agree with yours on matching the ppi to the scan aperture. I don't want to hijack this read... but it is generally regarded that a scan do do better than Photoshop in moving things up to size. Scanning a med format neg, for example, at 13 microns, would convert to a ppi of only 2000. I get exceptional quality scanning that neg at 8000 ppi. There is a slight advantage to doing it at 2000, but I think it is only a percent or two. Looking at the grain interpolating in PhotoShop will degrade one's image by 30 to 40% in comparison. (These are very subjective numbers, meant to be a comparison of my impressions only) It is always worth it, in my opinion, to set the aperture to match the grain effect you want and generate the amount of pixels you want.

Lenny

[widevista820]

Thanks to all who replied. I am indeed taking an 8"x20" negative and coming back out of the Epson with another 8"x20" negative. The reason I am scanning is to gain the ability to increase contrast for producing a Platinum Palladium print. The first negative thus far has produced a negative on the same quality as the original negative. Not real sure if the resolution is doubled if the results could be seen on an 8"x20 contact print.

-Bruce

[Ed Richards]

> Microcontrast of a drum scan will reveal all the nuances contained in the original - a consumer flatbed will lose some... It's not all just about resolution.

I thought the dynamic range of PT printing was about 1:64 tops, and more like 1:32, plus he is upping the contrast. I do not think micro contrast matters for this application. If money does not matter, might as well get the drum scan. But I am with Lenny on this - might as well also get a higher rez scan and get the operator to give you a downsampled scan as well if you cannot handle the full scan on your computer. You never know when you might decide you want to do a really big negative and a huge print. If money does matter, go with Bruce.