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I am new to digital photography, but I've been shooting with a Fujifilm x100s camera that saves to .raf format. When I use Fujifilm's .raf to .tiff converter, it asks me what dpi I want the image in. I think I'm a bit confused. If .raf and .tiff are supposed to be lossless, then when the .raf gets converted to .tiff, the dpi will be whatever is required by the original file? No? Maybe I'm missing something. Thanks all for your responses.

  • I pretty sure setting the DPI only changes the metadata of the file -- the DPI value usually relates to printing, which specifies the density of the dots laid down on the paper, and some layout software may use the value to determine how large the image should be scaled -- but regardless of what you put (72, 150, 300 are common), digitally the converted tiff files should be identical. – WClarke Dec 9 '18 at 7:58
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RAW files are not images and do not have attributes as DPI. Moreover DPI is interesting when you print the image. So when you convert RAW to TIFF this attribute is added from the software just in case (w/o specific reason)

For the test you can convert to TIFF with the same setting but different DPI and then compare those images and you will see they are the same (pixel by pixel)

  • You were right. Both tiff files were the same. So why the option? – sliderule3_14 Dec 10 '18 at 7:02
  • @sliderule3_14, this attribute (usually) is added by software for no reason. Maybe vendors think about moment in future when owner will want to print the photo. The only moment you will see it in use when software display the size of your imago in mm/inches – Romeo Ninov Dec 10 '18 at 7:06
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There is no real "DPI" in a photo. Inches of what? If it's a macro photography you can have tens of thousands of pixels for one inch of real life object, while pixels in Hubble images can be megaparsecs apart. Which is why cameras don't set the print definition in their JPEGs (when you see 72DPI it is just a default value, that corresponds to the definition of CRT displays of yore).

The TIFF file, being a format used for print, can have a print definition (which is merely "metatada", in other words, indications that can be changed), which in turns sets the intended print size (print size= size in pixels / print definition), so your software lets you set one if needed, but this is just for completeness and not terribly useful.

  • lol. dots-per-megaparsec. I love it! =) – scottbb Dec 9 '18 at 20:37
  • Actually, my cameras do include DPI in the metadata, and even have a menu item for setting it to whatever arbitrary four digits you want... I sometimes use this to store primitive information about old manual lenses in use. :) – junkyardsparkle Dec 9 '18 at 21:37

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