Digital image -> poster size print

[Reverend]

What is the criteria for blowing up a digital photograph to a 20 x 30 poster? I searched and couldn't find a definitive answer. Maybe I didn't have the right keywords in my search.

Is it a function of:

1.) Resolution (3456 x 2304)?
2.) DPI (I assume between 240 - 300 is an acceptable range)?
3.) megapixel capability (8 mp? more?) ?
4.) all of the above?

If more than 8mp is required, how much more?

Mods: seemed like a beginner's kind of question, but go ahead and move it if its more apporpriate in another forum.

 

[Digital Matt]

It's all going to depend on who is printing it, but in general, the only thing that is required is an image that is 6000x9000 at 300dpi. How you get this file is up to you. 6mp, 8mp, scanned film etc.... The end quality will be determined by how close your resolution is to 6000x9000 to begin with. Obvioulsy the more upsampling, (enlarging) you do, the worse it will look, but the quality is subjective. What one person might find unacceptable, might be perfectly acceptable to another. I've printed 20x30s from a 6mp camera, and found them to be quite acceptable by my standards, at a comfortable viewing distance of a couple feet.

 

[Reverend]

I assume that as long as the exposure is shot at a low ISO, with very little to no noise, then it would enlarge smoothly. Or are there more factors that go into this equation that I'm not considering?

 

[Digital Matt]

Using a tripod and mirror lock will help to increase the sharpness when enlarged.

 

[Reverend]

Using a tripod and mirror lock and all 'L' glass along with a Canon 5D will help to increase the sharpness when enlarged.

Fixed that for ya. :thumbup:

 

[D-50]

I agree with Matt I have seen 6mp pics (from a DSLR nto a point and shoot) blown up to that size and they look fine. If you have photoshop the resizing feature does a decent job if you use a bicubic smoother to enlarge. I would say enlarge a picture and have it printed and judge for yourself. worst case you think the quality is poor and your out the cost of the print job. Give it a try at staples first, theyt will print you something that size for very cheap, granted their printers do not make the best quality prints but it will give you an idea if your image will enlarge to that size without loosing too much quality. If you like the staples result go to a better print shop and spend a bit more to get a nice print.

 

[LWW]

Low dispersion glass will get better results.

Using a tripod will get better results.

Using a mirror lockup will get better results.

Using a faster shutter may will get better results.

Using a maximum DOF may get better results.

Using a program like Genuine Fractals will get better results.

LWW

 

[JodieO]

I just posted a picture of some 20x28s I had done that are hanging in my house from a 6 mp camera (here's the link http://thephotoforum.com/forum/showthread.php?t=50276) You should have no trouble blowing up to poster size with 6 MP (that was before I got a 12 MP camera). As far as resizing. My lab does that for me and does a wonderful job. I just crop to what I want, not changing DPI but letting it fall where it may, and my lab does the rest. Beautiful results. I have a 20x30 fine art canvas I just had done with the 12 MP and I didn't resize that either, it's beautiful!