Go Back   Steve's Digicams Forums > Digicam Help > Newbie Help

Thread Tools Search this Thread
Old Jul 29, 2003, 5:08 PM   #1
Junior Member
Join Date: Jul 2003
Posts: 3
Default Can anyone answer a (possibly) daft question?

I'm looking at buying a digital camera after seeing the images from a friends Sony 5MP camera on my computer.
The thing is, the images he downloaded were only 72 dpi even though he said the images were taken at the 5MP setting.
Is there any relation between the no. of megapixels and dpi? Or did he have it set at 5MP but low resolution?
Please help 'coz I'm confused!
pooley5 is offline   Reply With Quote
Sponsored Links
Old Jul 29, 2003, 5:24 PM   #2
Senior Member
Join Date: Dec 2002
Posts: 5,803

DPI really doesn't mean a lot on a monitor, and has even less meaning stored into a picture. I know of no good reason (except historical) for an image to have a DPI setting stored in it... especially an "out of camera" setting.

DPI stands for "dots per inch" (as you might know) but the monitor was already set at a resolution. How you display it is a function of the program, but is usually done by picking the size it is displayed at as a percentage (50%, 100%, 20%...) The DPI is ignored.

When you print, you want to specify a DPI. Then DPI makes all the difference in the world. (as you probably know.)

Most cameras can store the picture with varying levels of compression. Many can also specify storing at a lower resolution (fewer dots in the picture). But as far as I know, no matter what setting you choose (fine, very fine, low, high...) it will alway say 72DPI.

eric s is offline   Reply With Quote
Old Jul 29, 2003, 5:37 PM   #3
Senior Member
Join Date: Aug 2002
Posts: 2,162

Don't get even more confused!! The file you were given probably is a 5 Mpix image file, if using your image editor, you look at 'Image Properties' - it will tell the truth. Your Monitor can't possibly display every pixel in a 5Mpix image since it generally only displays 72 dpi or pixels per inch. If you measured it vertically and horizontally in inches, then multiplied each number by 72 and both numbers together, you'd get an equivalent size of about 790,000dots or pixels = less than 1M pixel!

Your file hasn't changed, but in order for your pc graphics card to show all the picture, it displays a sub sample (like a big thumbnail) of the real image by throwing away pixels BUT IN THE DISPLAY ONLY. This is called scaling and is done for editing. If you changed the image view option from 'fit to window' to 'show original size' your picture would look HUGE as you would be showing about 3/4 of a Mpix of your total of 5Mpixels in the file.

Now you can get the idea of how image digital zoom works - the displayed pixels are fixed, but you just throw away every other or so pixels in the much higher resolution input image to go from an apparent huge magnified image, to a shrunk one- even down to a thumbnail or little Icon! Exactly how the camera lcd or EVF display works. Check out this thread and some stuff I posted here:

voxmagna is offline   Reply With Quote
Old Aug 1, 2003, 10:21 AM   #4
Junior Member
Join Date: Jul 2003
Posts: 3

Thanks guys, that does make things clearer.
pooley5 is offline   Reply With Quote

Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off

All times are GMT -5. The time now is 5:45 AM.