Saving DPI ??

[Inspired]

Sorry this may be a dumb question, but i was wondering what DPI actually means, (i'm assuming its something pixels per inch?) and how you know what DPI something is when you save it?
I have seen written allot about sending things for print and saving at say 300dpi and then if its just for interenet use saving it at 72 dpi...how do i save something to 72dpi? And how do i check what DPI something already is?
TIA
Nicole

[Inspired]

Sorry this probably should have gone in technical?? Hope no one minds

[jev]

Dots per inch. And it's completely useless in most cases. Really, a 300 DPI 3000x2000 pixels will look exactly the same when shown on your screen as a 3000x2000 pixels image at 72 DPI. Things may be different if you print yourself or if you're gonna use the output in DTP software.

[Kym]

DPI is meaningless unless you know the monitor or printer resolution.

Pixels are the most important measure, and the DPI then expresses how big it will display...

3000 pixels will need 10" to display at 300 DPI
3000 pixels will need 41.67" to display at 72 DPI
3000 pixels will need 1.25" to display at 2400 DPI
etc

Thus to print an image at a given DPI on A4 size printer you know how many pixels you need (or can easily calculate that)

[ricktas]

Most monitors can display up to about 100ppi, so anything above that is not usually going to make your photo look any better on most monitors. In the past 72ppi was considered a 'standard' for web viewing as most monitors hovered around that resolution, but technology has gone past that now.

Printing on the other hand is different. If you save the same photo at 72ppi, and 300ppi and print it at say A3 size, you will see the difference, and the bigger the print, the more noticeable the difference. High quality printing should be from a 240ppi and above file. I save my print versions at 300ppi.

[wideangle]

Just make sure for printing that your images are generally above 200ppi, check with the lab your printing at as they do differ, the "Standard" is 300ppi, but there are professional labs that want prints sent at 200ppi, and to be honest I cannot tell the difference between 200 and 300 ppi on a large print.

[Inspired]

Most monitors can display up to about 100ppi, so anything above that is not usually going to make your photo look any better on most monitors. In the past 72ppi was considered a 'standard' for web viewing as most monitors hovered around that resolution, but technology has gone past that now.

Printing on the other hand is different. If you save the same photo at 72ppi, and 300ppi and print it at say A3 size, you will see the difference, and the bigger the print, the more noticeable the difference. High quality printing should be from a 240ppi and above file. I save my print versions at 300ppi.

Thanks everyone...I was just wondering as i was thinking if i just save my internet pics at 72ppi i would use less memory? or is that not right?

Rick and wideangle, when you say about saving at 200-300ppi for large prints is that just saving as "maximum 12' in CS4 or is there more to it than that? I would like to send a photo off to get printed off 20x30 and want to make sure its saved correctly so it doesn't print out all grainy etc. (I was thinking that was where the DPI thing came into it)...I think i'm making it harder then it is! lol

[ricktas]

Thanks everyone...I was just wondering as i was thinking if i just save my internet pics at 72ppi i would use less memory? or is that not right?

Rick and wideangle, when you say about saving at 200-300ppi for large prints is that just saving as "maximum 12' in CS4 or is there more to it than that? I would like to send a photo off to get printed off 20x30 and want to make sure its saved correctly so it doesn't print out all grainy etc. (I was thinking that was where the DPI thing came into it)...I think i'm making it harder then it is! lol

When you go - Image - Image Size - check the resolution in there. I don't use the slider in File Save, I use File Save for web, as it gives you more accurate control. PPI is pixels per inch. DPI is dots per inch and refers to how many droplets of ink a printer can lay down, so DPI is only really relative at printing.

[Inspired]

Sorry i must sound really dumb asking all these questions, but i'm looking in there now
and it says the following

Pixel dimensions 43.1
width 3168
height 4752

document size
width 13.2 (inches)
height 19.8 (inches

resolution 240 pixels/inch

So its the 240 i'm looking at?
If thats what it is when you open it straight from the camera, that is the largest it can go? but you can make it anything smaller than that?

[ricktas]

Yep, thats the one. At present your photo is set to 240 and yes you can change it. I am at work and don't have photoshop available to me to check, but from memory there is somewhere you can set the default. Mine is set to 300.

[Inspired]

Thanks Rick...i changed the pic itself to 300 but my default is still 240...If you get a chance, if you could tell me how to change the default to 300 it would be much appreciated.
Thanks again for your help
Nicole