EOS Rebel T7 How to take photos at 300 dpi

[Redsed]

I am just learning how to take photos of my artwork to post on a marketing site. I am told I have to post a min. 300 DPI photo which means I need to change my settings and photograph all my artwork...again.  Can someone give me a simplified explanation about how to do that. Sorry if this sounds a little crazy but I have put myself in a position to learn every. single. thing. about websites and social media and cameras all at once.  If I can just take the right pictures I will be miles ahead of where I am now. There are plenty of tutorials about what to put the setting on when you start out but not what any of those settings actually mean.  Thank you so much for any information. 

[Anonymous]

The DPI is only applicable when printing a photo. It is dependent on the resolution of the photo and the size of the print. To assign a minimum DPI to a photograph file that hasn't been printed yet, is meaningless. Typically, Canon cameras put a 72 DPI rating in out of camera files. It means nothing, as it is the DPI value if you printed the image at full size, which would be huge in size. In your printing software, the DPI value will increase with a smaller print size. The smaller the print, the larger the DPI value. If you have your camera set to its highest resolution, you shouldn't have to worry about the DPI value when taking the photo, it is the printing software settings that affect the DPI setting.

[Anonymous]

As an example, my camera produces a photo with a resolution of 6720 x 4480 with DPI value of 72. If I print the image at 72 DPI the image size will be 93.33 in. (6720/72 = 93.33) by 62.22 in. (4480/72 = 62.22). If I print the image at 300 DPI the print will be a 22.4 in. by 14.9 in. in size. So you can see the DPI is dependent on the image resolution and the desired size of the print.

[shadowsports]

In addition to Bob's detailed explanation 😃, ensure you are shooting in RAW format.  This allows the most creative flexibility.  You can use Canon's free Digital Photo Professional to edit, correct/enhance your images, and convert them to an easy to print, post format.  

Canon Support for EOS Rebel T7 | Canon U.S.A., Inc.

Its available for Windows or Mac OS

We'll be here to help 😃

[rs-eos]

The marketing site would need to at least provide one other value.  Just providing a 300 DPI value is not enough information.  e.g. that value implies you could submit a 300 x 300 pixel image that would print out as 1-inch square.

The site should additionally be providing either a resolution (width and height) or a physical size (width and height in inches).

Once you have the two values, you can then provide the necessary images.  e.g. if they want you to submit 8 x 10 inch photos at 300 DPI, that would mean you'd need images with a resolution of 2400 x 3000.

[Waddizzle]

I agree with Ricky.  They should also define an absolute image size, defined either in pixels or in/mm..  But an overall size specification is independent of a DPI specification.

If you are using a Windows laptop or PC, I suggest downloading Paint Dot Net to adjust the size of JPEG files.  You can upsize or downsize canvas size, image size, and DPI or PPI.  I do not know if this easy to use app has ever been ported to MacOS.

Paint Dot Net is easy to learn image editor.  It is a good introduction to how advanced imaged editors function.  It is far more advanced than MS Paint.  But nowhere near as complex as GIMP or Photoshop.  It is an image editor, not a photo processor.

[johnrmoyer]

You have received good information from others here about what DPI means. I am guessing you need to work around the ideas of the marketing site and not do not need to educate the marketing site.

I guess that a clueless marketing site might find it easy to have a computer program look at the image resolution values in the photo meta data. My Canon camera always puts a value of 72 DPI into both the RAW and JPEG files. If I edit the photo with Canon DPP free to download software, then DPP changes that value from 72 to 350. It might be that the only edits one would want to do are to crop, white balance, and digital lens optimizer, but the value would still change from 72 to 350 when a photo is saved. So, an easy way to change this value is to edit the photo, JPG or CR2, in the Canon DPP program and save it.

The free software exiftool program will display or change the value in the metadata. Changing the DPI value will not change the image, but in ancient times it would have changed how some web browsers displayed the image and how some programs printed it. https://exiftool.org/

exiftool -G0:2 -xresolution -yresolution -resolutionunit IMG_6277*
======== IMG_6277c.JPG
[EXIF:Image]    X Resolution                    : 350
[EXIF:Image]    Y Resolution                    : 350
[EXIF:Image]    Resolution Unit                 : inches
======== IMG_6277.CR3
[QuickTime:Image] X Resolution                  : 72
[QuickTime:Image] Y Resolution                  : 72
[EXIF:Image]    Resolution Unit                 : inches
======== IMG_6277cs.JPG
[EXIF:Image]    X Resolution                    : 350
[EXIF:Image]    Y Resolution                    : 350
[EXIF:Image]    Resolution Unit                 : inches
======== IMG_6277.dr4
======== IMG_6277.JPG
[EXIF:Image]    X Resolution                    : 72
[EXIF:Image]    Y Resolution                    : 72
[EXIF:Image]    Resolution Unit                 : inches

[johnrmoyer]

I re-read your question. I hope some of this might be helpful.

It is not clear to me whether you are selling the original art or are selling prints. I had previously guessed you were selling prints and the marketing site was doing the printing.

If selling the original art, then if the work is 20 inches by 30 inches, the photo would need to be 6000 pixels by 9000 pixels to have a 300 dpi digital copy of the original. Depending upon the marketing software, then one might be able to zoom in on the digital image to see brush strokes.

Since the Rebel T7i can produce an image of 6000x4000, if you had no margins this could sample an original art work at 300 dpi for a size up to 20 inches by 13.33 inches in a single image. If cropping margins from the photo or if the original is larger, then it would be necessary to stitch multiple photos together.

One could create a 6000x9000 digital image from photos made by a camera that has less resolution by stitching together multiple photos. I use the free hugin software to stitch images together.

[Waddizzle]

“ The free software exiftool program will display or change the value in the metadata. Changing the DPI value will not change the image, but in ancient times it would have changed how some web browsers displayed the image and how some programs printed it. https://exiftool.org/ “

Changing DPI should change how an image is displayed on a monitor.  Displaying an image on a monitor mean you use a different device Type.  Printers and Monitors have the same base class and share the same interfaces.

[Waddizzle]

This is what "Image Resize" dialog box looks like in Paint Dot Net.

Thre is a siimilar dialog box for "Canvas Resize".