Downsizing/downsampling for prints?

lenshood · Jan 1, 2022

Happy New Year, all.

I scan 6x6 negatives on an Epson flatbed, at 2400ppi. So this gives me a file that's roughly 5400 pixels on each side. Printing at 300dpi, I figure that is sufficient image resolution for an 18 inch square print. (If I've messed up that thinking, let me know! I'm pretty new to printing.)

My question is: is there any practical necessity for / advantage to downsampling that large image file if I want to print at a smaller size (say, 8x8)?

Many thanks-

wiltw · Jan 1, 2022

No reason to take the pains to downsize for smaller print dimension...

MattKing · Jan 1, 2022

Some labs won't accept a file that is more than 300 ppi.

lenshood · Jan 1, 2022

MattKing said:
Some labs won't accept a file that is more than 300 ppi.

Good callout, thanks - I neglected to mention I'm printing at home.

Alan9940 · Jan 1, 2022

I always scan at the maximum best resolution of my scanner, post-process to create a master file, then generate subsequent output from this master. The master never changes. Therefore, I will downsize, if needed.

grat · Jan 1, 2022

lenshood said:
Happy New Year, all.

I scan 6x6 negatives on an Epson flatbed, at 2400ppi. So this gives me a file that's roughly 5400 pixels on each side. Printing at 300dpi, I figure that is sufficient image resolution for an 18 inch square print. (If I've messed up that thinking, let me know! I'm pretty new to printing.)

Correct.

My question is: is there any practical necessity for / advantage to downsampling that large image file if I want to print at a smaller size (say, 8x8)?

Yes, and no. Since in this case, you're printing on a digital printer (to distinguish from printing on an enlarger in a darkroom), your printer has a maximum DPI for output. That might be 300 DPI for an older printer, or 1200 DPI (or more) for a newer one. The print engine on your software will handle the resampling necessary to print your image at 8x8, for example, with your guidance.

So resampling may happen, but you don't need to do it manually.

jgboothe · Jan 8, 2022

lenshood said:
Happy New Year, all.

I scan 6x6 negatives on an Epson flatbed, at 2400ppi. So this gives me a file that's roughly 5400 pixels on each side. Printing at 300dpi, I figure that is sufficient image resolution for an 18 inch square print. (If I've messed up that thinking, let me know! I'm pretty new to printing.)

My question is: is there any practical necessity for / advantage to downsampling that large image file if I want to print at a smaller size (say, 8x8)?

Many thanks-

The images will probably look ok printed at 18 inch, but with the Epson scanners the true optical capture resolution is always somewhat below the scanning resolution, so if it's a V700/800 series scanner, you will get a bit more detail by scanning at a higher resolution (up to 6400). You should see a difference in an 18 inch print. These can be downsized to 3200 with virtually no quality loss for more efficient storage. If you're using a V600 then 2400ppi may be giving you your maximum optical resolution already - I'm not sure as I haven't used that scanner.

As others have said, there's no real need to downsample for printing smaller, except that final sharpening is easier to judge with a file which has been resampled to the printing resolution.

Adrian Bacon · Jan 8, 2022

grat said:
Correct.

Yes, and no. Since in this case, you're printing on a digital printer (to distinguish from printing on an enlarger in a darkroom), your printer has a maximum DPI for output. That might be 300 DPI for an older printer, or 1200 DPI (or more) for a newer one. The print engine on your software will handle the resampling necessary to print your image at 8x8, for example, with your guidance.

So resampling may happen, but you don't need to do it manually.

+1

The only thing I'd add is that regardless of what the internet says, scanning at the native resolution of the scanner sensor is generally better, even if that means downscaling your master file down to the actual optical resolution of said scanner. Everybody is free to do what they feel is best, but I personally prefer to capture at the native sensor resolution, then scale down to the optical resolution simply because I prefer to have that control of that particular downscale and not leave it to whatever the scanner or scanner driver, or scanning software does. I have a V850 Pro that I use for digitizing reflective material and large negatives and that has been my workflow for a while. The v850 Pro tends to perform a bit better than what the internet gives it credit for.

lenshood · Jan 9, 2022

jgboothe said:
As others have said, there's no real need to downsample for printing smaller, except that final sharpening is easier to judge with a file which has been resampled to the printing resolution.

Ah, that is something I had not thought of, but it makes all the sense in the world. Thanks.

lenshood · Jan 9, 2022

Adrian Bacon said:
The v850 Pro tends to perform a bit better than what the internet gives it credit for.

That's interesting. I'm using a V850; I had been scanning at 3600, but didn't notice substantial reduction in quality when I went down to 2400 (which I did primarily just to reduce file sizes). Where are you seeing diminishing returns from increased scan resolution (if at all)?

Adrian Bacon · Jan 29, 2022

lenshood said:
That's interesting. I'm using a V850; I had been scanning at 3600, but didn't notice substantial reduction in quality when I went down to 2400 (which I did primarily just to reduce file sizes). Where are you seeing diminishing returns from increased scan resolution (if at all)?

It depends on what you’re scanning and which lens assembly you’re scanning with. You also need to keep in mind that if you’re going to evaluate the resolution performance, you should use material designed for that, as photos you’ve taken are going to be limited by your technic and picture taking equipment and will influence how much resolution you’ll perceive you’re getting.

all that said, scanner focus on the materials is critical. After that, each color channel actually captures a different amount of resolution, with red capturing the least, and blue capturing the most. If digitizing full color material, can’t do anything about that except capture at the max native resolution and scale down. When digitizing bw, it’s best to capture monochrome using the blue channel.

Downsizing/downsampling for prints?

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