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dpi or ppi
- Thread starter ziggy
- Start date
Hi Ziggy,
Basically DPI (Dots Per Inch) is used in Printing. PPI (Pixels Per Inch) is used for screen resolution. They are often interchangeable if you are printing from your screen to an ink jet printer. If you do professional printing you suddenly must be more precise and consider LPI. Here's one of the best descriptions (with history) of DPI, PPI, LPI which was written by one of the old time regulars on the Adobe Photoshop for Mac who owned one of the oldest service bureaus in Florida. Long ago he gave me permission to share it with others.
Basically DPI (Dots Per Inch) is used in Printing. PPI (Pixels Per Inch) is used for screen resolution. They are often interchangeable if you are printing from your screen to an ink jet printer. If you do professional printing you suddenly must be more precise and consider LPI. Here's one of the best descriptions (with history) of DPI, PPI, LPI which was written by one of the old time regulars on the Adobe Photoshop for Mac who owned one of the oldest service bureaus in Florida. Long ago he gave me permission to share it with others.
Welles, can you tell me why when I go into a picture into photoshop and then to image size why the reading is ppi 72? I know that this just simply can not be true. I shoot with a canon 20D on the highest setting....... I do do a lot of down sizing to place photos on the web, but, does photoshop read the last adjustment setting? Or is it reading the actual picture?
Also, if it is reading the actual picture what am I doing wrong with my settings in my camera!!! I am at a complete loss! I can not believe that my photos have such a low ppi. Also, does that mean that I can not print them in large sizes???? HELLLLLPPPPP!!!
THanks!!!!
Melissa
Also, if it is reading the actual picture what am I doing wrong with my settings in my camera!!! I am at a complete loss! I can not believe that my photos have such a low ppi. Also, does that mean that I can not print them in large sizes???? HELLLLLPPPPP!!!
THanks!!!!
Melissa
Welles your link is not connecting to this question. Can you send me a new link to that discription. I really dont understand dpi vs. ppi and then printing. If you want to blow images up really large how do you do that. Shouldn't the printer figure this stuff out?? Or do I have to figure it out and then send it to them?
Melissa,
When you open a picture in Photoshop it is reading exactly what your camera has captured. I believe it may be valuable to think in terms of pixel sizes rather than dpi or ppi. If your image is 2400 x 3000 pixels you have enough data to print an 8" X 10" at 300dpi. If you wished to put that image on this forum, for example, you would have to downsize the image to 600px x 750px to meet our size limitations.
There is nothing wrong with your camera settings, I suspect, it's just that Canon seems to have chosen to have their image formats at 72dpi, which happens to be a sort of Mac standard.
The PDF on LPI, DPI explained has disappeared with the move to the new forum so I'll repost it. Perhaps it is a bit technical but will help you grasp the issue of pixels/dpi/ppi/lpi. It seems complicated but with a little experience you'll find it isn't a big mystery. You may conclude as I have just to think in pixels.
When you open a picture in Photoshop it is reading exactly what your camera has captured. I believe it may be valuable to think in terms of pixel sizes rather than dpi or ppi. If your image is 2400 x 3000 pixels you have enough data to print an 8" X 10" at 300dpi. If you wished to put that image on this forum, for example, you would have to downsize the image to 600px x 750px to meet our size limitations.
There is nothing wrong with your camera settings, I suspect, it's just that Canon seems to have chosen to have their image formats at 72dpi, which happens to be a sort of Mac standard.
The PDF on LPI, DPI explained has disappeared with the move to the new forum so I'll repost it. Perhaps it is a bit technical but will help you grasp the issue of pixels/dpi/ppi/lpi. It seems complicated but with a little experience you'll find it isn't a big mystery. You may conclude as I have just to think in pixels.
Aha. We're posting at the same time! 
About printing. I'm assuming that you are referring to printing on your own ink jet printer? If your camera is saving it's files at 72 dip when you open the file in Photoshop, if you print at that resolution you will get a crummy print. For a good quality print, I use a standard print resolution of 300 dpi. So when you open an image in Photoshop, use Image > Image Size... Note the pixel dimensions. If you wish to print, change the Resolution from 72 to 300 in Document Size. Re-enter the original Pixel Dimentsions. Now the physical size in Document Size is what you can print at a high quality. If you need a bigger size your are going to be uprezing the image and Photoshop can do a good job, choosing Bicubic Smoother perhaps.
About printing. I'm assuming that you are referring to printing on your own ink jet printer? If your camera is saving it's files at 72 dip when you open the file in Photoshop, if you print at that resolution you will get a crummy print. For a good quality print, I use a standard print resolution of 300 dpi. So when you open an image in Photoshop, use Image > Image Size... Note the pixel dimensions. If you wish to print, change the Resolution from 72 to 300 in Document Size. Re-enter the original Pixel Dimentsions. Now the physical size in Document Size is what you can print at a high quality. If you need a bigger size your are going to be uprezing the image and Photoshop can do a good job, choosing Bicubic Smoother perhaps.
Thanks so much Welles, that is so interesting about the mac and the 72ppi in the canon 20D!!! I was really worried I was ruining all my images!!! WHEWW!!!! Thanks
It still is a bit foreign to me this whole concept and I read the article but it was a little Japanese-ish.... I was wondering if you send a print out to be printed shouldn't the printer change the ppi in order for the best print?? Or do I need to do that in photoshop before sending it out?
Thanks
Melissa
It still is a bit foreign to me this whole concept and I read the article but it was a little Japanese-ish.... I was wondering if you send a print out to be printed shouldn't the printer change the ppi in order for the best print?? Or do I need to do that in photoshop before sending it out?
Thanks
Melissa
When I go into image -- image size then I type 300 in the resolution. The photo turns into this enormous file that even when I view it at only 3% It hardly fits on my screen???
Am I doing something wrong or is this the file that I should send to the printer -- for real????
Excuse my stupidness on this!!! Sorry, this all seems like a different language!
Melissa
Am I doing something wrong or is this the file that I should send to the printer -- for real????
Excuse my stupidness on this!!! Sorry, this all seems like a different language!
Melissa
Melissa,
I've pre-answered that question.
After you increase the resolution to 300dpi, you should change the pixel dimensions back to what they were originally.
When you first open the Image Size dialog, note what the pixel dimensions are. Now change the Resolution to 300dpi. See the pixel dimensions increase approximately 4 times. Change the pixel dimensions back to their original size and the resolution doesn't change. Now with the original pixel size and the 300dpi, the Document size is what will print in inches.
It seems complicated at first but with a few practice prints it becomes 'normal' and does make sense!
I've pre-answered that question.
After you increase the resolution to 300dpi, you should change the pixel dimensions back to what they were originally.
When you first open the Image Size dialog, note what the pixel dimensions are. Now change the Resolution to 300dpi. See the pixel dimensions increase approximately 4 times. Change the pixel dimensions back to their original size and the resolution doesn't change. Now with the original pixel size and the 300dpi, the Document size is what will print in inches.
It seems complicated at first but with a few practice prints it becomes 'normal' and does make sense!
OH MAN YOU ARE AWESOME!!! OK, I think I understand now!! Thanks for putting this is laymans terms!!! (I am a layman!! LOL)
The only other question that I have now is do I have to do this for each different size like lets say I need a 5X7 and then a 16X20 do I need to make two different files with two different dimensions? Or is one file with the regular dimensions ok in a 300ppi? -- to send to the printer.
I really appreciate your help!!!
Melissa
The only other question that I have now is do I have to do this for each different size like lets say I need a 5X7 and then a 16X20 do I need to make two different files with two different dimensions? Or is one file with the regular dimensions ok in a 300ppi? -- to send to the printer.
I really appreciate your help!!!
Melissa