In EXIF data I see stuff like

XResolution = 72

YResolution = 72

I'm trying to display that on a site, and I was wondering if I should display both or just a single "72dpi" ?

Are there any cases when XResolution differs from YResolution ? I suspect it's not technically possible but I have to make sure :P


Yes, it is possible but extremely uncommon. This makes images that use rectangular pixels and require processing or special displays to appear undistorted.

Videos, before HD, made this the norm with pixel aspect-ratios of around 1.1 or 0.9 depending on which side of the Atlantic your TV was intended for. Some relatively recent cameras use this to save bandwith, again for video.

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  • The Nikon D1x had non-square pixels, but that's the only DSLR I'm aware of. – Matt Grum Jan 14 '14 at 12:12
  • I know its a video thing, but is this also applicable to Anamorphic film when digitised? – Digital Lightcraft Jan 15 '14 at 13:07
  • @DarkcatStudios - Yes. With anamorphic film, the shape of the negative is the same and the scanner used is the same which usually means it scan an evenly spaced grid. You have to interpret each of these as a sample from a rectangular pixel to get something which appears to be undistorted. – Itai Jan 16 '14 at 3:10

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