Printing images with noise?

I took some pics today that were at ISO of 800 and, given the lack of natural lighting, there is some with noise in them when I zoom in abit. A few of them I would like to print off at 8X10 and I am wondering how to judge which ones will be OK for that large of a print. Is there a rule of thumb, say 30% zoomed is the noise that will show on print at 8X10..... ? All the photos look great, until I zoom in a little bit, than those specks of noise show up. I am sure they are fine for smaller print (up to 5x7) with no noise showing, but am unsure how to know which ones are good for a larger print? I know that sometimes I do pixel peep, lol. I am over picky sometimes, but I see some noise specks when I zoom in and I wonder what sizes I can print them at, or if I should try at all....

What camera are you shooting with?

If it's a reasonably up-to-date DSLR then unless you have closely cropped then noise at ISO 800 shouldn't be a problem in an 8x10 print. Of course if you crop closely then it's like the zooming in that you did -- the close you get the more you see those little specs.

So look at it on your monitor at a "reasonable viewing size", other words approximating the 8x10 and I'd imagine that you'd be OK.

With old cameras as well as compact/P&S cameras, noise can begin to be a problem at say ISO 800, sometimes creep into say a blue sky or whatever, but again, an 8x10 is not much of a large print so you may find any noise just not bothersome.

A Rebel XS

Well, from what I know, I'd say you won't have "bad" images at ISO 800 unless you underexposed them and tried to boost them a lot in post processing. Not that you won't see any specs if you viewed them at 100%, but remember a 100% view is way bigger than an 8x10 print. You can use the 100% view to apply a touch of noise reduction but at ISO 800 I'd say only a small touch so you don't mess up the fine detail. Then, lower your zoom to, say, a 50% view and take another look. Or, in Photoshop, set the dimensions of your photo to the hoped-for print size and then using the Zoom tool select Print Size. It will not be accurate because of how each monitor has a different display resolution (you can "fix" that in Photoshop by getting your screen resolution an "plugging it in" to a Photoshop preference) but at least it will be more accurate than other zoom resolutions.

Oh, before setting the image dimensions to, say, 8x10, you want to have the prepared version cropped to that dimension, either in the Raw processor or in your image editor.

Finally, if you are still concerned, you can crop out a small portion of that image that would have say 4x6 dimensions or 5x7 dimensions and have it quickly run of at a one-hour-photo to check on that noise (don't expect a miraculous matching of colors and tones though).

What is your screen size and resolution and what setting do you have in

Edit/Preferences/Units and Rulers

Screen Resolution

It should be

Measure the width of your screen and divide it by your monitor's horizontal resolution.

Print Resolution

should be

the ppi you used when you resized for print... 300, maybe ?

Then select the hand tool and click on "Print Size".

This after you have done your final resize/resampling.

The image will display with the same dimensions as your print. It will give you a good idea of the noise and sharpness of your final print. You may notice that noise often is greatly diminished on a print since most people view an image on their monitors much larger than the actual print will be.

Seriously, unless it's really REALLY bad, only photographers notice noise.