Resolution, 72ppi??

[Steve U]

Would someone please explain to me the difference in quality and the science behind the numbers in my Canon 7D's rsolution of 72ppi and the guy beside me with his Nikon that has 300ppi resolution?


The teacher at the Photoshop class said most new cameras are 300ppi. Is it only Nikon?


I am led to believe that the resolution is a set number.


Thank you in advance,


Steve

[neuroanatomist]

Maybe because Nikon is exactly 4.167 times better than Canon? [A]


If you're talking about the numbers in EXIF data, it's pretty much arbitrary and irrelevant. You might also note that DPP defaults to an output resolution of 350 dpi, while I just noticed that DxO outputs to a default of 72 dpi. Like I said,arbitrary and irrelevant.


DPI only has meaning in the context of printing, where it is the physical density of the ink spots deposited on the print medium. It doesn't even matter what number for DPI is specified in the file information, because when you print a file the printer driver will adjust the output to match the resolution of the printer.


As far as I know, the only time the DPI setting would actually matter is when submitting the file to a publisher where their workflow involves offset printing, and they specify a size and a DPI setting for the file just to simplify their process (i.e. so they they can just insert into the layout without needing to change any values).

[tkerr]

Here is a good read


Image Resolution and Print Quality

[neuroanatomist]

Nice read!


Key point is that DPI matters only for printing. When submitting electronic artwork for print journals, for example, the usual guidance is 300 dpi for photos, 1200 dpi for line art, and 600 dpi for a combination of the two (e.g. a labeled photomicrograph). But print size also matters, obviously. So for example, if I want to submit a labeled photomicrograph as a 'two-column figure', those are printed at 7" wide, so my image would need to be 4200 pixels wide. If I don't have those 4200 pixels, I'd need to have the image printed as a single column figure (3" wide), or up-sample the image, which is a bad idea, since those pixels would be interpolated (= fabricated) by the software doing the up-sampling.


Hope that makes sense...


--John

[Steve U]

Thanks John, this Photoshop class I did was populated by a lot who know little, myself included and there was a fair bit of tsk tsk-ing and ,"only 72, heh" going on by the Nikon owners. The teacher did not have enough time to explain and reassure us Canon owners.


@ Tkerr your article explains it very well, image resolution is actually print resolution and does not effect or have any correlation to the viewable screen image.


Feel better now.


Cheers.