changing dpi

[triplefin]

I have a picture which is currently 240dpi I want to change it to 300 how will that affect it when it is printed or wont it?

[fishwhisperer]

Hi Jane,

The way I see it is....The more Dots Per Inch the more clearly the image is displayed at a larger size. e.g. If you had an image at 240dpi it would become pixalated far sooner than one at 600dpi on enlargement.

Hope you get what I mean...(I communicate much better underwater)

Steve.

[triplefin]

What I am really puzzled about it why it would appear that all the JPEGS i have taken this year are huge (print size) and the dpi comes up at 72 while the RAW files that I changed to JPEGS are much smaller pics (roundabout 20x15) and come out at 240dpi.

[Cerianthus]

It's just a setting; the only thing really important are the number of pixels. For screen viewing: 100% means 1 pixel in the file is 1 on the screen. For screen you use the number of pixels to resize.

Maybe your camera has a 72 dpi general setting somewhere.

For printing, you will need a minimium dpi for a good print. It is only the result of dividing print size and number of pixels. I dont think it is so usefull to set before..

[David P]

I fear it's one of the joys of Photoshop that I, too, wrestle with. As others have said, the key thing is the number of pixels not the dpi.

[KenByrne]

It gets confusing because screen resolution is in pixels per inch ppi and printing is in dots per inch dpi. It's seems to be recognised that 300 dpi is about as fine as our eyes can resolve detail and photo paper was supposed to be 300 dpi. Personally I find printing at between 200 and 300 dpi works for me.

What does this mean in practice? If you look at how many pixels there are in each dimension and dived that by 200 that is the size you can print at at 200dpi. so for a 6mp image which is 2000 by 3000 the the size is 10 x 15 inches. any larger and you may want to upsize the image by selecting the resample option in PhotoShop. I find the bicubic smoother works well for this. Also if you want to print to say A3 then it'll probably be fine anyway as you tend to stand further back when looking at a larger image.