Print size vs screen magnification

divamum

If I'm preparing a print for 8x10, approximately what magnification should I be looking at it onscreen to get an impression of the final image (file=50d raw file, thus 15mp) I realise cropping etc will impact this, but is there a rule of thumb?

Also, can the average picture accept more sharpening for print (vs screen) or the other way around? (I remember reading somewhere that you can/should use a heavier hand with one vs the other and now can't remember which it was....)

Thanks!!!

pathfinder

divamum -

I think you will want about 3000 pixels along the large length of your image - 10 inches x 300 pixels/inch. Some folks might suggest 3600 pixels, for 360 ppi, and I would not argue with them very much.

A standard 50D file is 4752 x 3168 so your basic RAW image should have pixels to spare without uprezzing any. I have made 13x19 in tack sharp images from 1/3 of a frame from a 50D..

Prints require more sharpening than images intended for the web. I use the sharpening for output in Lightroom when I print, and it seems to do a fine job.

High frequency images ( pictures of trees with leaves for example ) require a lighter touch than simpler geometric images.

divamum

Thanks Jim!

My reason for needing to know is because I have some files that have needed significant processing; I'm trying to figure out how "big" to look at them onscreen to get an impression of what it will look like in print, and how far I can push it before artefacting or other degradation becomes obvious...

Thanks!

colourbox

divamum wrote:

Also, can the average picture accept more sharpening for print (vs screen) or the other way around? (I remember reading somewhere that you can/should use a heavier hand with one vs the other and now can't remember which it was....)

Resolution is the key to your "how heavy a hand" question. Print has far higher resolution. On screen, one inch might only contain 80-100 pixels, while in print the same inch might contain 200 dots and up. If you applied the same sharpening settings to screen and to print, the sharpening will be less apparent at print res because the higher density would shrink the effect since the dots are smaller. So, for print, you definitely need to crank up the Radius and Amount roughly proportionally to the difference in resolution.

What size to look at on screen is not cut and dried. At 1:1 view, you are seeing every pixel, but a size you'd never see in print. At print size, you are seeing the right size, but each screen pixel has to represent many print pixels mashed together, and this unavoidably distorts the accuracy of evaluating the sharpening. Someone might have a better technique, but the best I can think of is to run some test output and get a feel for what certain sharpening settings/resolution combinations will produce on the specific type of printing you are after. The reason it is phrased that way is that even at the exact same sharpening and resolution, the same sharpening settings on inkjet will look different from halftone and dye-sub and chemical, and matte will look different from glossy. Like you see in Lightroom output sharpening with its Screen and Print, Matte and Glossy options. They try to account for that.

divamum

colourbox wrote:

Resolution is the key to your "how heavy a hand" question. Print has far higher resolution. On screen, one inch might only contain 80-100 pixels, while in print the same inch might contain 200 dots and up. If you applied the same sharpening settings to screen and to print, the sharpening will be less apparent at print res because the higher density would shrink the effect since the dots are smaller. So, for print, you definitely need to crank up the Radius and Amount roughly proportionally to the difference in resolution.

What size to look at on screen is not cut and dried. At 1:1 view, you are seeing every pixel, but a size you'd never see in print. At print size, you are seeing the right size, but each screen pixel has to represent many print pixels mashed together, and this unavoidably distorts the accuracy of evaluating the sharpening. Someone might have a better technique, but the best I can think of is to run some test output and get a feel for what certain sharpening settings/resolution combinations will produce on the specific type of printing you are after. The reason it is phrased that way is that even at the exact same sharpening and resolution, the same sharpening settings on inkjet will look different from halftone and dye-sub and chemical, and matte will look different from glossy. Like you see in Lightroom output sharpening with its Screen and Print, Matte and Glossy options. They try to account for that.

Very helpful - thank you!!!