The PPI setting really has no effect on the quality of the image. Regardless of whether it is set to 72 PPI or 240 PPI, the image will still have precisely the same dimensions.
Thanks for your reply. But why can't I stipulate the dpi setting for my exported Jpeg?
I don't know why you can't change the setting on the exported image. It works for me. I'm just saying that if you think you are improving the quality of the image by doing that, you are misinformed. Could you provide a screenshot of your export settings?
Yep - working here too. I've just exported a file at 200 ppi then 2000 ppi, and the different values are in the metadata of the two exports, just as they should be,
Being only a metadata tag it makes no difference whatsoever to anything else about the file of course, but it's there.
My understanding is that a 72dpi file is OK for web work but to produce a high quality print, I would need a resolution of say, 240dpi. Or am I completely misunderstanding how L/R works?
I've just done some more testing and the problem appears to be with the software I was using to look at the Jpeg. When I looked at the metadata in P/S the resolution was as I was expecting. Obviously my trusty (and simple) Capture NX2 will have to be slung, as there is some sort of incompatibility problem - probably because it hasn't been updated for some time.
Apologies and many thanks for you help.
You are misunderstanding what DPI is.
Your image has a size in pixels, for example 4000x6000 pixels. This is the true size of the image.
When you send the image to a device that has a variable dots-per-inch (or pixels per inch) -- like a printer -- you can change the DISPLAY size of the image. This does change the quality of the displayed image. If you try to make a small image (800x600 pixels) display at 72 DPI to fill your paper in the printer, the image quality will be bad due to the pixels being too large on the paper. Small pixels print the best, say 220 DPI or higher. That means you need a goodly number of pixels in your image for a large print. For example, at 300 DPI an 8x10 inch print needs 2400x3000 pixels.
All screen display programs ignore any DPI data in your images since monitors are not variable DPI devices. Most print programs take the DPI number under advisement while asking you to override the number by having you pick the size of the print display you want and then recalculating the DPI for that size paper.