Lieutenant Junior Grade
hi, i just got a scanner and i'm a little confused by the relationship between dpi and picture size. it seems that when i increase the dpi, i get a bigger picture (even if i preset the size i want). i thought dpi was purely for quality, so if i scanned at 75 versus 300, it just means the 300 is better quality. can someone clarify? at what dpi should i scan to get the same exact size as what i scanned (ie. scan a 4X6 picture and be able to print that same 4X6 picture)? thanks!
Don't think of the size of your scans in terms of inches, but think of them in terms of dots.
Your monitor can probably display images somewhere around 100 dpi (dots per inch), depending on how you set your resultion. So, if you scan an image at 100 dpi, it will appear to be the same size on your screen.
If you scan the same image at 300 dpi, it will take three times the amount of dots on each edge to display the same image- and you may have to scale it to fit it on your screen.
Now, to answer the question as to what resolution you should scan at, you have to know what the resolution of your printer is. If your printer can print 300 dpi, then scanning at 300 dpi will give you the same size when you print.
So, higher dpi does mean higher quality, but only if you can USE it. If you are doing any editing of the photos, higher dpi is a must, so that you can zoom in close to an area and still see everything clearly. Even then, though, I don't think I will ever scan anything at 1200 dpi! (But that's just me...)