Quote:

Why do some Canon cameras set the resolution to 180 DPI?
For the longest time, I tried to figure out why the Canon 10d generated photos that were tagged with a resolution of 180 DPI. Why not 300? After giving it some more thought, it likely that they wanted the 6.0 megapixel camera to automatically imply a print size of 11 x 14 inches for advertising purposes (but notice that this requires a lower resolution than the 300 DPI that is standard for printing).

Quote:

There are three issues that you have brought up... it turns out that none of them are actually related! I'll try to give you an idea of each:

• DPI - The DPI setting that each camera sets for an image is essentially meaningless. They could have set it to 1000 DPI and it would not have changed the image. The DPI setting is basically a way of telling your photo software / printer what the default image size should be, but you can set it later to whatever dimensions you like (at the expense of resolution). This DPI value has confused a lot of people!
• Image Sharpness - Most digital cameras require some degree of sharpening (due to the way that the sensor is arranged/used). Point and shoot cameras tend to do this in-camera, while digital SLRs leave it up to you. If you are seeing differences in image sharpness for the same composition, etc., then it may be due to differences in quality of the lens, the use of digital zoom, and image processing in the camera itself. Canon is fairly well regarded for image quality, so it wouldn't be too surprising to see a difference.
• Image Quality setting - Unfortunately, the names and meanings of the quality setting is completely vendor-dependent. In other words, each manufacturer chooses its own names for their highest image quality setting. Some use fine while others use super fine or maximum. You cannot compare quality settings between different manufacturers for many reasons (if you are interested in the details, read about quantization tables). But, in general, one should always use the highest quality setting, and simply reduce the image size if you are tight on space. Lower image quality settings (while they reduce file size) introduce some pretty unpleasant compression artifacts that may be much more frustrating than a smaller image!

Quote:

You don't need to, and in fact cannot, change the DPI resolution as recorded by your camera. To be completely honest, it's a meaningless number. Your camera records a fixed number of pixels (3.2 million) in large mode. It is your choice (in the photo editing software) what physical dimensions you want for the final print. Obviously, the larger the print, the lower the DPI that you are effectively using.

When enlarging, it is best to choose a minimum DPI that is acceptable for your final output (most people aim for 300 DPI, but 240 or even 200 may be acceptable). Since your camera records 2048 x 1536 pixels, this means ~ 5" x 7" @ 300DPI, 6.5" x 8.5" @ 240DPI or 8" x 10" @ 200DPI. You can define this resolution (or conversely, output dimensions) in Photoshop (via the Image Size dialog using the Resample option). This will override any DPI setting that your camera may have written into the original file. The whole concept of DPI settings from the camera has certainly confused a lot of people!

Just as an aside, the superfine mode simply describes the level of compression that you are using (not resolution), which is another contributor to overall image quality.