72 DPI vs 180 DPI?

Question

I Just bought the Panasonic FX07 (7.1mp) and so far I am very please with it. I just have one question... my other camera - the Canon S1 IS (3.2mp) takes pictures at 180dpi, and my new Panasonic which has 4 more megapixels takes pictures at only 72 dpi.

Is this a problem? What difference will I notice (because I’m having a hard time finding one now)

I found this out by looking at the advanced properties of the pictures from each camera.

Answer 1

Pictures that are stored digitally have dimensions that are measured in pixels, not in inches or any other physical measure.
Your 7.1 mp pictures are approximately 2175 pixels high and 3265 pixels wide. (A pixel is a "dot.")
Pictures only acquire physical size when you print them or display them on a screen. If you print them on a 4 X 6 piece of photo paper, then the picture is 4 X 6 inches. If you print them on a huge 30 inch by 45 inch poster, then the picture is 30 X 45 inches.
DPI (dots per inch) is just arithmetic: it's the pixel size divided by the print size. That little 4X6 picture is 2175/4 = 543 dpi; the big poster is 2175/30 = 72 dpi.
JPEG pictures store a bunch of information internally about the picture, and for some reason, they decided to store dpi as well as physical size of the picture, but as I said above, it doesn't mean anything. You will also probably also see that your picture dimensions are 30 inches by 45 inches. It doesn't mean you have to print tremendous posters from your camera: you can print them in any size you see fit.

Answer 2

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 3

As far as my knowlegede goes, it's simly a setting for screen viewing (pixels) and printing (dpi). Some print shops want you to tweak the dpi for their printers (like to 300dpi) bescause their printers don't autoscale. Most home printers do fine without tweakig the photo.

Here's a good discussion, better than I could do: http://www.13dots.com/forum/index.php?showtopic=15401