CAN the res on 20D be changed from 72 to 300?

You can change it with the Viewer App that comes with the Canon utility's.

It's icon is a panoramic with a magnify glass, it's found in the Canon Utility's / Photostitch / Program (Mac)

Just drop your image on it it's on my Dock i use it to view at 100% (or use the open command on Windows) then go to FILE / OPTIONS then enter the new amount you like.

Or try using of the other Canon apps.

RAW files out of the camera are 240 dpi and JPG's are 72 dpi.

cdi-ink.com wrote in post #2383836
Actually when you use the smaller fine settings, it doesn't compress anymore than the large fine. It just produces a dimensionally smaller file so that the data size is inherently smaller. Same goes for large normal and small normal. Smaller dimensions, same quality. I used the small fine/normal when I was shooting for the newspaper.

Agreed. I don't think I claimed that small fine compresses more than large fine. Actually small fine seems to have a slightly lower degree of compression than large fine, on average, if the numbers in the manual are to be believed.

But on an 8mp Canon like the 20D, the average file size is 1.2mb for small fine. For 0.6 mb you need to use small normal, where the JPEG compression ratio is about 10. In my experience that's around the threshold where artefacts can occur. Small fine has a compression ratio of around 5, large fine is around 7, and these should be essentially artefact-free.

StewartR wrote in post #2383809
I don't think that's right. You're comparing apples with oranges.

Your 20D can produce 6 different types of JPEGs. You have 3 sizes (large=8.2mp, medium=4.2mp, small=2.0mp) and 2 quality levels ("fine" and "normal"). The average file size varies from about 3.3mb for large fine, down to 0.6mb for small normal.

I'm not sure which Nikon you're comparing it with, but let's take the D70 as an example since it's of similar vintage. It has 3 sizes (large=6.0mp, medium=3.3mp, small=1.5mp) and 3 quality levels ("fine", "normal" and "basic"). The average file size varies from about 2.9mb for large fine, down to 0.2mb for small basic.

So the 3.5mb files you get are the best quality JPEGs you can get from your camera. But these 500kb files that the Nikon users get are amongst the worst that their cameras can produce. You can get a 600kb JPEG from your camera, if you want to compete with them, by setting it to output "small normal" JPEGs. Of course, you're only using 2mp instead of 8mp, and that level of JPEG compression will probably show artefacting - but you can do it if you really want to.

Or you could get a cameraphone instead.

i hear what youz sayin - and although my general question was answered, ill go further here since im confused about it ... im seeing other dudes shooting with nikon d200s delivering (right off the cam, no post processing) 2544(w) x whatever @ 300 DPI/PPI (whatever) and they are avg 500kb. im shooting large fine (3504x2336) since my client wants printable (and since i dont see a 300ppi setting on the cam, and since i understand the concept that 300/72 doesnt matter anyways)

so technically, im delivering a better print quality jpg than the doodz sending 500kb pics at 300dpi

doesnt make any sense to me that an image of 2544 w dimensions @ 300ppi @ 500kb avg, is of the same or greater quality than a 3.5mb avg pic @ 3504w @ 72ppi

my math is correct though, no? divide dimensions / 300 for aprrox print size?

mky219 wrote in post #2384147
so technically, im delivering a better print quality jpg than the doodz sending 500kb pics at 300dpi

Absolutely.

To get a 3500x2500 pixel jpg image to 500KB, you must heavily compress it ... resulting in a loss of image quality.

If your boss is fine with that, then maybe his application is not very demanding (e.g. newsprint or internet images).
I'm exaggerating a bit here, but try to offer a 500 KB image to Playboy or Vogue, they'll fall out of their chairs laughing.

Best regards,
Andy

If you save 2 jpg files one with quality Maximum 10 or 12 and the other with quality lowest 0 or 1 you'll see the difference in quality even with a high number of pixels (forget that ppi figure - unless you're printing).

20D RAW image saved at max jpg = 3.49Mb
20D RAW image saved at min jpg = 174Kb

Both are 3504 x 2336 images........

It's mainly the compression that determines the file size.