What pixel size and PPI do I need for good 10x15 cm prints, and how can I reduce JPEG upload size?
Asked 8/25/2010
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2 answers
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I’m using a Canon 400D and my JPEGs are typically 3888×2592 pixels, with file sizes around 3.5–6 MB. I want to make good-quality 10×15 cm prints (about 4×6 in) and also upload the files faster. What pixel dimensions/PPI should I aim for, and should I resize or recompress the JPEGs before printing or uploading?
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
16y ago
2 Answers
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JPEG Quality of 9 ~ 10 out of 12 (or 70 ~ 84 out of 100) is pretty indistinguishable from uncompressed. See this article for an in-depth comparison. In short, if you have less color gradients, you can get away with higher compression (lower quality values).
For PPI (what you care about), in general, 240 to 360 PPI is high quality. This depends on typical viewing distances and your audience. For example, with posters where people won't be walking up to and scrutinizing, you can get away with lower PPI because the viewing distance is further.
Ideally, you should find out what the printer's native PPI (not DPI) is and use a quality program and algorithm to resize (including upscaling) to that resolution, as opposed to letting their software or printer do the resizing.
To calculate the number of pixels, simply take your desired physical output size, convert to inches if necessary, and multiply by the PPI:
10 cm by 15 cm
x 1 inch / 2.54 cm
x 250 pixels / inch
= 985 pixels by 1477 pixels
10 in by 15 in
x 250 pixels / inch
= 2500 pixels by 3750 pixels
Originally by user389. Source · Licensed CC BY-SA 4.0
user389
16y ago
0
Generated from our catalog & community — verify before relying on it.
For a 10×15 cm (about 4×6 in) print, 300 PPI is a solid target for high quality. That works out to about 1200×1800 pixels. More generally, 240–360 PPI is considered high quality for prints viewed at normal distances.
Your original 3888×2592 files already exceed what’s needed for a 10×15 cm print, so you do not need to upscale anything. You can either leave them as-is and let the lab resize, or resize them yourself to roughly 1200×1800 using a good resampling method.
If your goal is faster uploads, lowering JPEG compression quality slightly is often enough. Saving at around JPEG quality 9–10 out of 12 (roughly 70–84/100) is usually very hard to distinguish from maximum quality, while reducing file size.
In short: for 10×15 cm prints, aim for about 1200×1800 px at 300 PPI, and if you want smaller upload files, keep the same dimensions or resize appropriately and save with slightly lower JPEG quality.
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