Why some Digital Cameras take photos at 72dpi while some others take photos at 96 to 300dpi?

Question

I know that Sony and Fuji Digital Cameras record the photos at 72dpi being at Hi Resolution settings, while Digital Cameras like Canon and Nikon record the photos at 96dpi to 300dpi being at Med to Hi Resolution settings. I have a Fuji Finepix S5100
4 Megapixels and I set the adjustments at the highest photo quality and the result is a photo at 72dpi. Why is that?

Answer 1

You can not control the pixels per inch in your camera, as this is a function of the sensor. I have found the following ppi for SOME cameras by the following manufacturers. I wonder if this specification is available anywhere. I have four camera manuals in front of me and I can't find it in any of them.

NIKON - 300 ppi
CANON - 180 ppi
PENTAX - 72 ppi

We "discussed" this by way of question and answers a while back and decided that the ppi file produced by the camera really did not have any effect on the capability to produce a good print. If I take a photo with my wife's 6 MP Nikon and view the image on the screen, it will start out as 300 ppi. If it's a full frame image of 3008 pixels x 2000 pixels, the SCREEN image would be pretty big if I viewed it full sized, but it would print 10.0" x 6.6". If you crop a 5x7 out of this, keeping it as full-frame as possible, it becomes 400 dpi.

With my brother's 6 MP Pentax, the image is 2816 px x 2112 px, but it's at 72 ppi. If you print this without cropping, it would be 39" x 29"!!! If you crop a 5x7 out of this, though, it becomes 402 dpi resolution, which is virtually identical for the Nikon 6 MP camera.

With my son's 6 MP Canon Powershot A620, the image is 3072 px x 2304 px, but it's at 180 ppi. If you could possibly print this without cropping, it would be 17.1" x 12.8". If you crop a 5x7 out of this, though, it becomes 439 dpi resolution, which is a bit better than either of the other 6 MP cameras.

In other words, regardless of the sensor's pixel-per-inch output, 6 MP cameras produced the same resolution when it came time to print comparable images. How about a camera with more pixels?

If I take a photo with my 10 MP Nikon D200 and view the image on the screen, it will start out as 300 ppi. If it's a full frame image of 3872 pixels x 2592 pixels, the SCREEN image would be pretty big if I viewed it full sized, but it would print 12.9" x 8.6", if I had the right paper. If you crop a 5x7 out of this, keeping it as full-frame as possible, it becomes 516 dpi, or higher resolution than the 6 MP cameras. We knew that is would work out like this, though, didn't we?

The REAL question is, what difference does this make in the real world? If we agree that 300 dpi is an excellent resolution for prints, as long as you end up with at least 300 ppi after you are done cropping on the screen, you will get an excellent print as far as resolution goes. All four cameras exceed that amount. I usually resize "down" to 300 dpi before printing, because you can't tell the difference above that resolution anyway. Most people would be quite happy with a 200 dpi print, so go ahead and crop a bit. If you get a print resolution too much below 200 dpi, you will start to see digital artifact in the print and it will be objectionable.

Answer 2

The photo quality has more to do with the total number of pixels, rather than the dpi. It's complicated.

The dpi rating affects the screen display and printing of photos.
A high-res monitor will display 1024 x 768. That's only 0.7 Megapixels. That's why a full-screen image like wallpaper looks bad when printed at 8" x 10" That 0.7 MP image has been reduced to about 100 dpi for printing.
A good quality photo at 4 MP will give more than 200 dpi, so a printout at full page size will produce a decent image.

Photo-editing software can change the relationship between dpi and physical size.
A photo printed at 72 dpi will be bigger than a photo printed at 96 dpi, although the source file will be the same size for both pictures.
Another way of saying it is: the same data spread over a larger area.

A 14" TV looks good from a distance of 12 inches. A 36" TV looks crappy from a distance of 12". The same picture data has been spread over a larger area.

Answer 3

DPI usually refers to printer quality, not camera resolution. This may help:

http://electronics.howstuffworks.com/digital-camera2.htm