How do I make sure digital prints aren't blurry?

July 14, 2007 9:15 PM

How can I be sure that my digital photos are not blurry before printing them at 8x10?

I've decided to enter some photos in my county fair. Prints entered have to be 8x10 and are "not to be altered by computer." I take that to mean that I cannot use a sharpening filter on them. They also must be printed from a lab -- no home printing.

My photos are taken with a 5mp camera at 2560x1920.

I've had pictures from this camera printed before, and while some turned out quite lovely, others are blurry when they're actually in my hands. I need to know what I can use to be sure that a picture is clear enough to be printed at a photolab, as I am not interested in having a ton of prints I can't use around. I do not have a color printer to test a picture and I'm not sure that would be helpful, anyway.

I am using Mac OSX on a Macbook and I downloaded the Aperture trial today. The loupe tool is way cool but I'm not sure what I'm seeing with it. If something is blurry in the magnification does that mean it will print badly? Is there something else I can use to make sure before I get a given photo printed?

Thanks in advance. If I win a ribbon it will be all thanks to you.

posted by sugarfish to media & arts (15 comments total)

The easiest thing to do is simply view the image at full size (ie, not zoomed in at all - the image will be twice the width and more than twice the height of your Macbook's screen) and look at edges; if they're blurry, your print will be. 8x10 is about the limit of what you can print off of a 5-megapixel shot, but the results should be fine if the shot itself is sharp enough.
posted by Tomorrowful at 9:27 PM on July 14, 2007

In Aperture, if you press the 'z' button, that zooms in the whole screen to view the picture at the pixel level. Press 'z' again to go back to the regular view. I often use this more than the loupe.
posted by alidarbac at 9:32 PM on July 14, 2007

I don't know anything about Aperture, but I know a thing or two about photoshop and outputting files. You'll want the original image to be 8X10 ( 2400 x 3000 pixels ) at around 300 dpi. Once you start dipping below around 250 dpi is when things start getting blurry.
posted by quadog at 9:41 PM on July 14, 2007

"Not to be altered by computer" is a really strange stipulation because most RAW files look very flat before processing since they're capturing a very wide dynamic range. Similarly, sharpening almost always needs to be done so that the picture looks sharp in it's final form. This means that pictures intended for the web need more sharpening than pictures intended for printing.
posted by bshort at 9:44 PM on July 14, 2007

Zooming in to full size is good, but sometimes that's too close. Just be sure you are viewing at 25%, 50% or 100%. Other scales can look really pixely and blurry on screen, even though the image is sharp.
posted by The Deej at 10:02 PM on July 14, 2007

"Not to be altered by computer" says "film" to me. Before you go to any effort, I'd check with the organizing body to make sure digital prints are acceptable at all, and if they are, exactly what "altered by computer" means. (It could mean that you have to use the image straight off the camera; it could also mean you're not allowed to drastically alter the composition in Photoshop.)
posted by mendel at 10:14 PM on July 14, 2007

Seconding mendel. Find out what the exact rules are.

Sharpening with Photoshop is exactly the same as the sharpening algorithm on your camera, so it would be nonsensical to disallow the Photoshop version but allow you to turn your camera's setting to "sharper".

Also, pros that shoot in RAW routinely (must) adjust colors and sharpening before printing. Again, this is the same process that could have been done in the camera.

Many organizations that do accept digital photos will allow basic level adjustment, color tweaking, and sharpening, but draw the line at pixel editing or anything that makes an unrealistic picture.
posted by mmoncur at 10:48 PM on July 14, 2007

This is a county fair. There's a very good chance they don't have a whole ton of technical expertise and actually do mean "Don't do anything in photoshop", because they may not really be aware of RAW images at all. But the only way to find out for sure is to find out the exact rules.

Zoom in all the way as describe earlier. Be warned that stuff will not look absolutely as crisp as possible; digital camera technology makes things a little blurry when the camera or your computer demosaics the raw data into something that can be displayed or printed.

The only real thing you can do is try a bunch of them at varying degrees of fuzziness and see for yourself what results meet your criteria for sharpness.
posted by aubilenon at 1:07 AM on July 15, 2007

Yeah, use your digital camera, just don't do any alterations in photoshop/picasa/etc. Try using a tripod for blurriness. It helps not only with camera shake, but also seemed to help my older cameras get a better auto-focus on the subject. Take your photos in the highest resolution and highest JPEG quality possible. If you shoot RAW, processing it to an equivalent JPEG isn't going to violate anybody's rules, and no one will know anyway.
posted by DarkForest at 3:27 AM on July 15, 2007

"Photoshopping" to me means altering the meaning of a picture - putting a piece of cheese on a picture of the moon, or superimposing Bush's face on a chimpanzee.

I expect that any of the standard post-processing (levels, contrast, saturation, sharpness) will be perfectly fine. These are already done in the photolab, the camera, and the printer, so it would be arbitrary and uninformed to say they cannot be done on the computer.
posted by SNACKeR at 6:06 AM on July 15, 2007

Many organizations that do accept digital photos will allow basic level adjustment, color tweaking, and sharpening, but draw the line at pixel editing or anything that makes an unrealistic picture.

Right. If the contest committee doesn't understand the difference between toning and optomizing color and contrast in photoshop, and changing the editorial content of the image, then they have no business making rules like that. Toning (and even burning and dodging) are routine parts of producing a professional print from a negative. It would be unfair to prevent the same techniques from being used by a digital photographer.
posted by cowbellemoo at 8:24 AM on July 15, 2007

Thanks, all. I'll mark some best answers after I get some prints. I agree that the rules might be weird -- digital cameras are specifically allowed, btw -- but I also think if I start calling and trying to see how much computer altering is allowed then I'll look suspicious.
posted by sugarfish at 6:40 AM on July 16, 2007

One of the best ways to make a photo "crisp" without unshark mask or high pass filter techniques is to correct color fringing or chromatic aberration. I would not count this as computer alteration, but I'm curious what some other photogs who may have entered competitions might think.
posted by Pastabagel at 7:42 AM on July 16, 2007

You say you're using a 5 MP camera, so even if the photos aren't blurry, you might get pixelation trying to print at 8"x10". Here's a chart that gives pixels vs. print size necessary to get photo quality printing.

I've printed 8"x10" photos off a 7.2 MP camera, and they looked just fine. 5 MP might be pushing it. Just something to be aware of beforehand.
posted by Gamblor at 9:09 AM on July 16, 2007

So I ended up using the Z tool in Aperture to decide which pictures were clear enough to enter, which worked fabulously. I got prints from Adorama and found out last night that I'd won a blue and a pink ribbon. Thanks again, everyone.
posted by sugarfish at 9:08 AM on August 5, 2007