Urgent! DPI question

Hi folks,

I'm preparing to hand in my photography assignment next week and I've suddenly realised I haven't a clue how to properly print my work!

I have four images: two are 6" x 11.7"; two are 11.7" x 6". I will be printing on a Canon Pixma MP150 on A4 matte photo paper.

Before I realised my problem, I was working at 72 DPI. Is this sufficient enough?

What should I do? Help!

No, 72 dpi normally is not sufficient for print. Remember, your digital images have no physical size; they can only measured in pixels. So when you mention size in inches you haven't told us anything about the size of you images. Generally you want to print at between 200 and 300 dpi (actually ppi). To determine the needed pixels to print your images at a given size, multiply the desired print dimensions by the desired dpi/ppi. So to make prints of your images at the size you mention @300 dpi, you will need at least 1800 x 3500 pixels. (6x300 X 11.7x300) Conversely, to determine the size print you can make from an image divide its' pixel dimensions by the desired dpi/ppi.

Thanks a lot, Jim! You are a star.

I'll see how I fare at 72dpi for the time being and work from there.

Cheers!

72 dpi is WAY too low for prints that are being examined closely. 250dpi or 300dpi is what you need. Also I find printing at home a pain in the butt, I use a lab.

Thanks for the input, Tim. I'll try printing at 72 tomorrow and if it's diabolical... well, I've got some work to do!

Paul, how big are your images? Most Dslrs output images that easily make 300 dpi prints at the size you want. I'm thinking you may be a little confused on this dpi thing...

tim wrote in post #3064728
72 dpi is WAY too low for prints that are being examined closely. 250dpi or 300dpi is what you need. Also I find printing at home a pain in the butt, I use a lab.

Actually it all depends. The "ppi" of your image depends on the final output size to your Ink Jet and you WILL need Photoshop to resize this most accurately.

Here's an example:

With the RebelXt you capture a file that is 48" x 32" at a RESOLUTION of 72ppi (this is the full size from an 8MP camera).

If you have a device that will out put an image at 48" x 32"(100%) you can print it as is at 72ppi since you output at 100% of the ORIGINAL file as shot.
Now on the Ink Jet you can set the DPI to 720 and that would be enough for good output.

Now in Photoshop in the image size box, UNCHECK the "resample Image" box
and then in the width field type in the size you want so 11.7" and Photoshop will show you what the Height will be (7.8") and notice the image RESOLUTION "ppi"
is now 295.385 (that's ppi Pixels per inch NOT DPI).

Photoshop has just told you that if you want to print this file at 11.7" x 7.8" the optimal resolution is the 295.385.

With this you can now make the out put setting on your Ink Jet for 720 dpi (dots per inch) and you will get a good sharp output (assuming your file is sharp or what ever style you shot)

so an image out put at 100% of it's original size at it's original resolution (if 72ppi) will print fine.
As you reduce the physical dimension of the image the reolution will increase accordingly in Photoshop if check or uncheck the correct boxes.

Sorry, when I said dpi I meant ppi. Really the ppi is irrelevant, so long as for a 12" wide image you have 3600 or so pixels the image will be fine.