Do I need to change 72dpi for printing enlargements?
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Suvv
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- Kev
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First off your camera does not produce images at 72dpi or any other dpi it just produces pixels. 72 is a figure that is put into a "box" as something has to go in there 
DPI is only of interest when printing and nowadays we should really be saying PPI as it stands for Pixels Per Inch. It is easy to work out the PPI of an image by simply dividing the number of pixels in, for example, the width of a picture by the printed width of the picture. So if you had a 3000 * 2000 pixel file and printed it at 10" wide it would have a PPI of 3000 pixels divided by 10" or 300 Pixels Per Inch (300PPI)
So you do not have to batch change your photos but when printing them you know what the pixel dimensions are and you know what size you want printed so can work out the PPI - the software normally does that for you and displays it
You can then decide if you need to resample the pixels, that is create new ones to get a high enough PPI. Most people quote 300PPI for printing but I have good results at much lower PPIs although below 200PPI even I can notice the difference
DPI is only of interest when printing and nowadays we should really be saying PPI as it stands for Pixels Per Inch. It is easy to work out the PPI of an image by simply dividing the number of pixels in, for example, the width of a picture by the printed width of the picture. So if you had a 3000 * 2000 pixel file and printed it at 10" wide it would have a PPI of 3000 pixels divided by 10" or 300 Pixels Per Inch (300PPI)
So you do not have to batch change your photos but when printing them you know what the pixel dimensions are and you know what size you want printed so can work out the PPI - the software normally does that for you and displays it
You can then decide if you need to resample the pixels, that is create new ones to get a high enough PPI. Most people quote 300PPI for printing but I have good results at much lower PPIs although below 200PPI even I can notice the difference
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But the end-result print contains dots, not pixels so dpi is still valid
snappingsam
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depends on your lab - many will ask for the file to be sized to final size at 300 dpi....
MattHall
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I've known Labs wanting 300dpi, 350dpi and one in Bradford needs them to be a strange 402dpi!