Confused about image resolution and printing

[Jie Kageshinzo]

I understand that for web-viewing purposes, 72 DPI is enough for good resolution. However, when it comes to making prints for your artwork, you have to have it at least 300 DPI.

1. What would prevent people from changing the DPI to 300 using Photoshop, etc.?

2. This might be answered by no. 1 as well but, when do you specifically make an image high-res or lo-res, before saving your PSD to JPG/TIFF/etc? Or you can make it high-res or lo-res anytime you want?

3. Say you're being commissioned by someone for an artwork, how do you send them a high-res artwork? Do you send them the PSD file itself, or do you flatten your PSD image, save it as 300 DPI (or higher) JPG/TIFF/etc and then send that to them?

Sorry if they sound particularly noobish. I'm just concerned that I may be uploading high-res, printable images in the future and not know it. :/

Thanks for the replies!

[crossmirage]

1.Changing the DPI wouldn't make an image good for print because it's like blowing up the size; if it's low-res to begin with, you can't make it "high-res" no matter what you do.

2. That is determined when you first create your document. After that you can't go back and fix it.

3. You send the image in the resolution/DPI you worked with. I usually do what you mentioned, flatten and save because unless the client specifically requests it, they may have no use for it.

[Tmza]

[Jie Kageshinzo]

2. That is determined when you first create your document. After that you can't go back and fix it.

You mean, the first screenshot that Tmza attached above?

[crossmirage]

Yep, that.

[Elwell]

I understand that for web-viewing purposes, 72 DPI is enough for good resolution. However, when it comes to making prints for your artwork, you have to have it at least 300 DPI.

Talking about dpi (more properly, ppi) independent of image size is useless. For instance, the same 1500x2100 pixel image would be 1.25"x1.75"@1200ppi, 5"x7"@300ppi, 10"x14"@150ppi, and almost 21"x30"@72ppi. So, to address your concern about file sizes and posting, the 600x1000 images in your sketchbook would be 2"x3.33"@300ppi. They could be printed up to twice that size and maybe be acceptable, if a little soft, but any larger than that and you're going to get noticeable noise/blurriness/pixelation (depending on the up-sampling method).

[Baron Impossible]

I understand that for web-viewing purposes, 72 DPI is enough for good resolution.

This is where you're going wrong. DPI (PPI) only - ONLY! - has meaning for the printed image. You can view an image at 1 DPI or 28398342 DPI on the screen and there is no difference. 72 DPI and 96 DPI are legacy values with no meaning. Forget about them.

As Elwell says, when you print you need to know two of -
DPI
Printed size
Pixel resolution

If you know any two you'll know the third. One, however, isn't enough.

Don't feel too bad, though. Not so long ago I had an an art editor say that they would like the final preview images (of a specified pixel dimension) sent in 72 dpi rather than 300 dpi to minimise the size of the email. Unbelievable.

[Jie Kageshinzo]

This is where you're going wrong. DPI (PPI) only - ONLY! - has meaning for the printed image. You can view an image at 1 DPI or 28398342 DPI on the screen and there is no difference. 72 DPI and 96 DPI are legacy values with no meaning. Forget about them.

As Elwell says, when you print you need to know two of -
DPI
Printed size
Pixel resolution

If you know any two you'll know the third. One, however, isn't enough.

Don't feel too bad, though. Not so long ago I had an an art editor say that they would like the final preview images (of a specified pixel dimension) sent in 72 dpi rather than 300 dpi to minimise the size of the email. Unbelievable.

Yeah, I was talking about printing physical images, not the resolution it will look like on the monitor . I was able to read about DPI and PPI and their differences so I sort of already know that DPI doesn't do squat when it comes to monitor viewing. It's just that I've been readin how 72~96 DPI will not look good in prints and that 300 is recommended for good prints. Sorry, I wasn't too clear about that in my original post. >_<x

In any case, thanks everyone. I think I already know what to do now.

[Baron Impossible]

Yeah, 300 is always best if you can manage that. I've had a couple of recent jobs where I needed to print 1m+, and therefore we used 150 dpi. Before I did that I did a test print on 100 DPI and whilst it wouldn't look particularly good for text or patterened graphics, that was fine for 25"+ for painterly stuff.