dpi output of dslr's

[woodyew]

Hi everyone, I have a question regarding dpi output of dslrs. Why would I consider dpi output when purchasing a new camera. I am looking at the Canon 7d (72 dpi) and note that some nikons have a dpi output of 200. As far as I understand it the output will not make any difference to how a photograph is seen and anyway the dpi can be altered in PS. It has been suggested to me that there will be more information in a higher dpi output camera.
Suggestions please.
Thanks in advance,
Paul.

[Glenn NK]

I'm not aware that the term "dpi" applies to camera sensors. This is a printing related term.

Sensors may be rated in MP per mm2 (megapixels per square mm or cm if you wish).

The pixel density cannot be altered in the processing of an image.

There will be more information in a camera with a higher pixel density. The 7D has a relative high pixel density.

Perhaps the term you are thinking of is PPI:

http://en.wikipedia.org/wiki/Pixel_density

Glenn

[Manfred M]

You are a bit confused; cameras do not have dpi, they have sensors and their output is whatever the manufacturer has chosen as a sensor design. In my camera, I get 7983 × 4394 usable pixels on a sensor that is 24mm high and 35.9mm wide; no more, no less, so camera sensors are looked at based on their pixel pitch and total pixel count (MP).

Screens are usually looked at in PPI (pixels per inch) and printers generally have a native resolution that is discussed in terms of DPI (dots per inch). All that the PPI or DPI give you is how large the image will scaled on your output device, whether it is a screen or print.

[pnodrog]

The PPI and or DPI (different usage similar result) at 72 will relate to the information set at the start of the JPEG file. It can be easily changed and apart from outputting to a printer has little practical affect unless you are trying to view the image at a specific scaled size. It certainly has nothing to do with camera performance.

[Jestertheclown]

All is revealed!

[Geoff F]

Just be careful when it comes to printing etc, Paul.

As previously mentioned, it is the total number of pixels which matters not the ppi resolution. If your software gives the resolution as 72 ppi (or 96 ppi with European monitors) you will see an apparently extremely large image size.

But if you tried to print at that setting you would get a large poor quality blocky looking print. However, most printers automatically resize the resolution to suit the print dimensions.

But if cropping/resizing check that you are changing the number of pixels and the resolution remains suitable. Most software will do this automatically but I have made mistakes when working to a fixed dimension, in inches/mm or pixels, and I have changed the wrong box!

With some software, it is necessary to set the correct ppi resolution to achieve the required image size and doing it in the wrong order won't deliver what was intended.

And some photo printing companies want your files at a specified resolution (usually 300 ppi) although it doesn't really matter providing you have sufficient pixels. In fact 'printing' at a specified resolution of 200 ppi usually gives just as good a print as 300 ppi.

Printers don't actually print at these settings, it is just a format which is supplied to the printer. But it does give you a chance to check that you will have sufficient information supplied to the printing equipment.

As previously mentioned, printers work in dots per inch which is something totally different.

ps. I find my 7D produces images which are often much bigger than I would ever require, and consequently take up a lot of storage space. So I sometimes resize them downwards as part of the editing process. Then still end up with excess pixels.

But I always retain the original Raw image so I have an opportunity to return to that and do another edit if I ever required an extra large image size.

[jcuknz]

I have three cameras .... a Canon with 72 dpi, a Panasonic with 180 dpi and a Nikon with 300 dpi
Obviously the Nikon is the best camera