Need a quick primer regarding DPI

[Iron Flatline]

Hi all.

A friend of mine needs a camera that can produce a 300 dpi file. I told him if he shoots RAW he can then set a dpi in the editing software - a camera has no native dpi per se as it has a simple sensor array - there's width x height, but that has no effect on the actual dpi on the final file.

Am I right? Or am I not getting this.

I told him if he shoots JPGs there may in fact be a dpi factor applied to the file by the camera.

Please remind me how this works. Thanks.

 

[JamesD]

A pixel is a pixel is a pixel. Determine the dimension, in inches, you need, then multiply by 300. That's how many pixels wide/long your file needs to be.

Save the original for future editing.

 

[Digital Matt]

Jpg, raw, tiff, doesn't matter. You can change the resolution independent of the pixel dimensions. DPI is a setting interpreted and set by the printer.

 

[Big Mike]

DPI is a printer setting (how many dots of ink get laid down per inch).

PPI is pixels per inch...is used to determine how big the image will appear on a monitor screen. You can change the PPI setting to 72, 300, 3000 or 12...it won't necessarily change the image at all (providing that you don't re-sample and keep the same number of pixels).

What it comes down to...is the number of pixels in the resulting image file. The rule of thumb is that you want 300 pixels per inch of print size. So if you want an 8x10 print, you will want a file that is 2400x3000 pixels. You can print with less than 300 pixels per inch of print or you can re-sample the image to add pixels, within reason, to get bigger prints.