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Author Topic: canon jpgs are all 72 dpi?  (Read 3275 times)


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canon jpgs are all 72 dpi?
« on: January 17, 2014, 04:03:23 PM »


did some shooting and thought I would use the highest canon t3i jpg setting instead of raw. got home and found all the images are only 72 dpi!
well not used to seeing images at 72. I suppose they will print out just as well esp when I make them into panoramas. did some 8x12 at 72 dpi and they looked ok. not a technician here as far as all that dpi stuff but just surprised they were so low for highest jpg setting.
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Re: canon jpgs are all 72 dpi?
« Reply #1 on: January 17, 2014, 04:36:19 PM »

The dpi figure is arbitrary in this case. A 4000x3000 pixel image at 72dpi contains the same amount of info as a 4000x3000 pixel image at 360dpi.   ;)  Specific dpi settings can be useful for printing, though.

You can probably change your camera's default dpi if you want. Otherwise you can change it in editing with most software.


D Fosse

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Re: canon jpgs are all 72 dpi?
« Reply #2 on: January 17, 2014, 07:12:45 PM »

Ppi is a print parameter, it's irrelevant until the image hits paper. A pixel is just a pixel, but on paper that pixel needs to have a physical size, which is what ppi defines. Ppi is metadata that can be arbitrarily changed at any time without affecting the image data.

On screen there is already a screen pixel grid, so it's just a question of mapping image pixels to screen pixels. A 1:1 mapping, aka 100%, is always the most accurate. So again, ppi is wholly irrelevant.


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Re: Canon JPEGS are all 72 ppi?
« Reply #3 on: January 21, 2014, 09:06:24 AM »

First of all—it's ppi, not dpi. Okay? Please!

And then, 72 ppi is exactly right for out-of-camera pictures. It means, 'output resolution is unknown/undefined.' After all, a digital camera is not an inkjet printer. Read the EXIF specification.


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Re: canon jpgs are all 72 dpi?
« Reply #4 on: January 21, 2014, 12:40:30 PM »

Not just Canon, nearly all the cameras generate jpeg at whatever the resolution is at 72 ppi. Part of it is a leftover from when all monitors were 72 dpi and 640x480 was a high-res camera.

Though it makes the image seem larger than life, it's nothing to worry about. Simply resize your image to 300 ppi or your favorite output res when you are in Photoshop. It's as simple as going to Image-->Image Size and then make sure the "Constrain Proportions" box is checked. You can then make your image from 1 ppi (or ppcm) to 9999 ppi, or anything in between.

For most, 300 ppi seems to be the norm for printing and most print media and 72 ppi for web.

The real issue I have is when a noob asks me for an image at 300 ppi and gives me no other info. I usually ask them back if they want an image that's one inch at 300 ppi or one that's 100 inches at 300 ppi? Then I can usually ask the right questions for me to properly prepare the image for their use.

72 ppi or 300 ppi, is simply too ambiguous, like "send me a jpeg file no larger than 2 MB". I wish people would simply spec the number length and width of pixels they need along with file type/compression, etc.
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Re: canon jpgs are all 72 dpi?
« Reply #5 on: January 21, 2014, 02:42:51 PM »

ppi is meaningless until you look at it on a screen.

A 4000x3000pixel image is a 4000x3000 pixel image irrespective of what ppi your software says. (and when you print, ppi is completely unrelated to dpi)

Or, to cut a long, convoluted and widely misunderstood story short, you have nothing to worry about.
"Reality is an illusion caused by lack of alcohol."
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