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Old Nov 8, 2006, 9:35 AM   #1
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I have Photoshop Elements. Image size is shown in inches and in pixels per inch. I oftenmake printsthatshowed 240ppi as the resolution. I read that 300 dots per inch is the point at which prints look best. I know that 240 pixels require more than 240 dots to reproduce as the printermay laydown several droplets tocreateone pixel. Does the printer software convert to a fixed number of dpi? Is there a way for me to control that soI always print photos at 300dpi or higher?
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Old Nov 8, 2006, 2:52 PM   #2
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Ppi means nothing till an image is printed.

The pixels per inch depends on the number of pixels in the image and the size you print it at.

In other words, a 3000 x 3000 pixelimage printed on 10in x10in paper is a 300ppi image.

Print it at 20x20 inches and the pixels are spread out over a larger area and it becomes a 150ppi image.

In most software photoshop, psp, etc you can change the ppi (without resampling) and the "size" of the image (in inches or cms)changes or you can change the size of the image (in inches and cms) and the ppi will change but that is ignored totally when you actually come to print.

My SonyH1 for example sets the ppi at 72, so when I load it into an editor it is reported as being a 72ppi image, but only when printed at 36in x 27in !!!

If I was to print it at 9in by 6.75in then the ppi of the image would automatically (and without me having to specify or change anything) be 288ppi..
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Old Dec 24, 2006, 2:13 AM   #3
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I often make prints that showed 240ppi as the resolution.
If your prints are showing 240 PPI after you size them for printing you will get very good prints. I ran some tests on a couple of my photo printers and found that I couldn't see any improvement over about 240 PPI even with a loupe.

I would not resample them up to 300 PPI. You always lose just a little definition with a resample and I see no reason to do that.

My printers might be different from yours though. Make some smaller prints by cropping so you get 300 PPI. The easiest way to end up with exactly 300 PPI is to uncheck resample and set 300 PPI in the resolution after you crop close to what you need. It isn't important that the print be an exact size. Compare those with 240 PPI prints. My guess is that you won't see any difference. I usually put four on the same sheet of paper.

You can also resample one up to 300 PPI and compare with the native print at 240. I think the 240 PPI print will be at least as good.

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Old Dec 26, 2006, 8:32 AM   #4
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You need to do a little more reading regarding Pixels Per Inch and what's required for a "good quality" print.

Read this from Smugmug to see how they make their prints. If there's one thing I've learned in having Smugmug do prints for me up to as big as 16x20, it's better to let them do any needed interpolation..


and this related message board. Shay Stephens knows what he's talking about;


Up to around 8x10, 300PPI is at or justbelowwhat the native resolution is for 6-8 megapixel cameras. My 8 megapixel DSLR is still well over 300 PPI (I believe the exact number is 326.4 PPI)at 8.5x11, or A4 sized paper.A 4x6 print's native resolutionfrom a6-8 megapixel camerais well over 400 PPI. Until your native resolution drops below 150PPI, meaning we're talking abouta pretty good sized print (around 16x20 for an 8 MP camera), I don't know why you'd even need toup sample, and to be honest it'd be interesting to see how much difference there is, if anyat all, up to 11x14 printed at 240 PPI vs. 300 PPI. I would bet we couldn't tell a difference viewed from an appropriate distance, not 6 inches andwith a loupe....

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