Question Megapixel And DPI?

Is there any difference between megapixel and dpi? Or are they the same? I know dpi is dots per inch.

When I take my photos into photoshop and check the image before I mess with it it says 72 dpi.

So if were to scan in a 3 x 5 film photo would I be able to make a nice 8 x 10 with that like I could if I took it with the photos I took with my xti at 10.1 megapixel?

Also, maybe not the place to ask this but I want to scan in some old photos and they are a photo print and I think they are a 3 x 5 maybe. I want to be able to take them on a flash drive to make a nice 8 x 10 so should I scan them in at as high as dpi as I can? or is 100 dpi good enough or more?

sorry staying up late and playing around.

Thank You

There is a very big difference. A digital image is measured in pixels wide and pixels high. Width times height gives resolution in megapixels.
When Photoshop says dpi it really means ppi, pixels per inch. That is the number of pixels that will go in to making one inch along the edge of a print. Usually, 300 dpi is considered best for optimum quality. That means that for an 8x10 print you need [8x300=2400 pixels]x[10x300=3000 pixels]. If you are scanning a 3x5 photo, in order to get the needed 2400 pixels along the short side you divide 2400 by 3 inches which gives you 800. If you set the scanner to 800 dpi you will get a 2400x4000 pixels image which can then be cropped to 2400x3000.

.. but even then, you won't get any detail in the 8x10 print that wasn't in the 3x5 to begin with. (And the ratio is different by the way, so a 3x5 would give a 6x10)

If you can find the negative somewhere, and scan that in a film scanner, all problems will be solved.

Or a 8x13.3

Yeah, but my math had just run out...

JC, if it is showing 72 dpi, that's the way you have it set up in your preferences menu or maybe somewhere else.
I have mine dialed in for 300 dpi.

Someone will chime in to tell you where to change it.

chauncey wrote in post #6981896
JC, if it is showing 72 dpi, that's the way you have it set up in your preferences menu or maybe somewhere else.
I have mine dialed in for 300 dpi.

The "72 DPI" number is embedded into files created by most Canon EOS DSLRs. It means absolutely nothing and should be totally ignored. The only thing that matters is the pixel count in the image. Software will take care of resolution issues when you define the print size you wish to make.

When you want to make a print and you care about the minimum resolution, merely divide the dimensions of the intended print into the pixel count of the image for the related dimensions.

I absolutely NEVER down-size a print before sending to a printer (or having it printed commercially). There's no benefit whatsoever and you will definitely lose quality in your image doing so. There's absolutely nothing wrong about having an image that has twice (or more) the minimum resolution that you wish to print with.

My bad, I ass-u-med that you were in Photoshop.

Ook wrote in post #6976449
If you can find the negative somewhere, and scan that in a film scanner, all problems will be solved.

I agree that would be your best option. You can buy scanners that have attachments to put the negatives though as well... or bring the negatives to a store and have them scan them and burn to CD (I asked at our local Walmart, they said it would be 3megapixel images.. I don't really know about other places). That would be fine for 8x10 anyways.


It depends on how detailed you want your picture to be.. I've scanned 4x6 image and I think it would look "OK" printed at 8x10 (perhaps a little sharpening would help).

I have some old surfing photos of me that I want to scan in and make into a 8 x 10. I do not have the negatives. I lost them a long time ago. I will probably just scan in at a high dpi and crop and sharpen.

Thank You