Canon EOS Digital Rebel XT photos are stored at 72 dpi and not 180 dpi. Can I change this?

[MacKenrick]

When I download my photos taken with my Canon EOS Digital Rebel XT to my computer I notice that they are listed as 72 dpi but when I download photos from my smaller Canon pocket cameras (like my Powershot S410 or ELP 300) they are listed as 180 dpi.  Is this a function of the cameras or is there some setting I can change on the Rebel to store the photos at 180 dpi?

My second question is:  will it hurt the quality of the printed photo if I manually "resize" the dpi to 180 in a photo program before printing.   The vast majority of my photos are just snap shots that I print at 4"x6" but occasionally I get a good photo that I like to enlarge.

As you can see I know very little about digital photography.  In the past I haven't even noticed that the Rebel photos were at 72 dpi and the others were at 180.

Any information that will educate me on this subject will be greatly appreciated.  Thank you.    Mac

[eulothg]

DPI which stands for Dots Per Inch only matters when you actually print the image.  DPI for a digital image is a bit of a misnomer and it really doesn't matter what it says in the EXIF data if that's where you are seeing the DPI rating.

The Rebel XT has an image size of 3456 x 2304 on the Large setting.  If you print this image at 72dpi you will get a 48 x 32 inch print.  The quality won't be very good as there are only 72 dots for every inch of the print.  If you print the same image at 180DPI you will get a 19.2 x 12.8 inch print which will look much nicer but be considerably smaller.  Most reasonably quality laser printers will print at 300dpi which puts you in a 11.52 x 7.68 inch print range.  So the largest recommended size print for the XT would be an 8x12.  Anything larger and it will start to look blocky.  Anything smaller will be just fine.

[MacKenrick]

Thank you eulothg, for your response.  I am seeing the 72 DPI information when I right click on the image file in Windows Explorer and select the details tab.  I also see the 72 DPI information when I bring the image up in Paint Shop Pro.  But as mentioned, my other photos taken with "pocket" cameras show thier DPI at 180.  I was curious as to why the Rebel (the better camera of the bunch) shows up at 72 DPI when the cheaper pocket cameras show up at 180 DPI.  I was also curious if "resizing" the image (to say 180 DPI) in a photo program would improve the printed photo (especially if the printed image were going to be printed in a smaller physical size such at 4x6 or 5x7)?

I think I understand your explanation but am a little unsure about "printed sizes" of photos.  If a photo taken with the Rebel (that shows it is 3456 X 2304, 72 dpi which is apparently at 48 x 32 inches) and send the photo in to be printed at a physical size of 4x6 inches, does that mean that the printer automatically resizes the photo to the highest DPI the printer can print at (possibly 300 dpi).

[eulothg · Accepted solution]

If you tell the printer to print a 4x6 print it will not (generally) pay any attention to the image's indication of DPI.  All of the shots from my XSi are 72DPI as well and I've printed many images at about a dozen different locations throughout the city and the DPI setting in the image file is ignored in favour of the printer's resolution and the image size.  That is, if the printer does 300 DPI then my print comes out at 300 DPI.  I've never seen a case where the printer used the DPI setting in the file.  I cannot guarentee that won't happen on some printer, somewhere.

But most people don't print that many images in that many locations so I suspect if you simply print a single image at any "new" printing locations you can determine if it will go badly or you can take the time to set the DPI setting on the image with your image editing software.  I'm not sure what you are using to edit your images, however, the following two software packages let you adjust the DPI or print resolution:

Irfanview lets you alter that setting: http://www.irfanview.com/

GIMP also lets you alter it: http://www.gimp.org/

[MacKenrick]

Thank you eulothg,

That is exactly what I needed to know.

[eulothg]

Glad I could help.  Cheers 🙂

[Tobago13]

I have a related question. I am not interested in printing but I take photos of my artwork and need 300 dpi to send in to competitions.  My understanding is that setting the image size in photoshop  to 300 dpi from 72 dpi doesn't change the resolution. I have taken shots with a small canon point and shoot at up to 240 dpi but obviously the lens affects the outcome. Can the rebel be changed to 300 dpi? I also want to have 300 dpi images to make high quality prints for giclees.

[Mykolas]

Hi Tobago13!

There is not a setting in the camera to change the dpi of the recorded images.  However, if you use Canon's Digital Photo Professional, you can process an image by selecting it and clicking on the [Batch Process] button.  You can set the preferences of the output file including the dpi.

If this is a time sensitive-matter, additional support options are available at Contact Us.

[eulothg]

Hey, Tobago13.  If you look a little higher in the thread you'll see a more detailed explanation, however, what it boils down to is that DPI only has meaning for prints.  If you are submitting photos digitally, there's no such thing but it's a common misunderstanding.

For good quality prints, make sure you avoid cropping your images as much as possible.  Most digital cameras today will print fine on an 8x10 or 8x12 as long as you are printing the full image and it's hasn't been cropped too much.

[edfadude]

I know this is an old thread, but I have had problems with the 72dpi tag many times.  I agree that it is a meaningless number on an image file, but there are web-sites that have idiotic dpi requirements instead of an image size requirement for when you submit images.  It is annoying to have to manually edit my images every time I need to submit a check deposit to my bank (for example).  Canon really should provide a setting on the camera to store a user specified dpi number to our images.