What image size do I need to print a 4'x4' photograph?
April 30, 2012 9:14 PM   Subscribe

DIY Photo Art Question: I would like to have a photograph or image professionally printed onto canvas or good print-quality paper, about 4' x 4'. What do I need to know?

The image will be framed and hung in a stairwell. I'd like to one of my own photos (maybe tweak it with photoshop first), or else find one for free or for cheap online.

(1) What is the minimum resolution that I am looking at here (again, the image will likely be 4-5 feet wide and 4 foot tall)? Is there any other quality issues that I should be aware of (I am a newbie with image files)?

(2) Does anyone know of any websites that sells these kinds of photographs or images? Or offers them for free?

posted by ageispolis to Media & Arts (8 answers total) 7 users marked this as a favorite
To print on canvas, you probably want at least 150 dpi (dots per inch). That's what Canvas On Demand, the canvas printing service I use, requests. That means that for a 4' by 4' print, you want the image to be about 7200 x 7200. That's really really REALLY big.

It basically means "upsampling" the image in photoshop unless you have access to some truly enormous files. This works best with pictures that are soft and blurry anyway, where it doesn't matter if they get a little blurrier in the upsizing (partially out of focus flowers, clouds, abstracts of water, that sort of thing).

It's easy enough to upsample an image in photoshop, but you have to start with a pretty big image. I'm not sure exactly where you might get them -- I always just use my own (which start out about a third of the required size from a digital SLR). I don't think it's that expensive to buy them at istockphoto and places like that, for one-time private use.

Another quality issue is you want to make sure to "soft proof" your image. Canvas on Demand allows you do download their icc profile so that you can see how your photo will look printed. (Their printer/ink/canvas combo tends to print a bit bright and blow out the whites a tad, even after you soft proof). To soft proof, however, you need to have a profiled monitor. If this paragraph makes no sense at all to you, I'd find a friend who does understand it, or call the company up and ask them to "eyeball" the image for you and adjust accordingly. Again, since Canvas on Demand (I swear I don't work there, I'm just their best customer by now) is perfect, they will do this for you; they offer cheap editing of your photo, as well as upsizing. I'm not sure if other canvas printing services will do this; probably they will though if you call.

Good luck, feel free to PM me with more questions. I just printed a 4' x 5' image for above my bed -- best $$$ I ever spent!
posted by bluesky78987 at 9:47 PM on April 30, 2012 [1 favorite]

There isn't really a minimum resolution, it's more a case of keeping the pixels small enough that at your expected viewing distance they're not individually visible.
If by "hung in a stairwell" you mean on the wall at eye height that people will pass within a foot of, then that's pretty much worst case scenario - extreme close range viewing distance of a large print - and you'll want either a high res image, or to make a decent interpolation. At that (closely examined) distance, thanks to the canvas texture, I'd think you could get away with 50 pixels per inch (ie an image about 2500x2500) if it's high quality (ie not riddled with jpeg artefacts, which will show up pretty nastily at that kind of resolution. Not a lot of pixel noise or hard transitions). If you don't know a lot about your camera settings, chances are that your images will have a bit too much noise and artefacts at this kind of res.
A safer option would be for an image of 3000x3000 or higher, and interpolate it up to 5000x5000 (which smears the pixels out a bit, making them slightly less intrusive) or if you can get at non-interpolated image at that resolution, go for it! (but it's actually pretty unlikely to be uninterpreted)

Basically, take a look at some of your photos zoomed right in, so you can see the pixels. If you can now see all sorts of artefacts and noise, you'll want to clean it in photoshop before printing (hell, do that regardless). If there is a lot, it might not be easy to get nice results.

Also remember, you could cut one sixteenth of your photo out, and print it on canvas at 1x1 foot as a cheap test-print, and see how it comes out. That will be very informative, and that knowledge will make you feel much more secure about ordering the 4x4!
posted by -harlequin- at 9:49 PM on April 30, 2012 [1 favorite]

Since the technical questions are answered...

Try Costco.com or go to the store. You don't have to be a member to get your pictures printed. Just go to the customer service desk or some Costco stores have a photo section right next to the customer service desk.

Also check out Groupon. I get e-mail notifications regularly for canvas prints that are very affordable.
posted by Yellow at 4:55 AM on May 1, 2012

as far as finding images, check out sxc.hu for free stock art
posted by pyro979 at 6:19 AM on May 1, 2012

If you can plan the photo and shoot something specifically for this rather than using something you already have, you could do a composite photo and stitch it together using tools in Photoshop or little open source utilities. (Not really an option for stuff that moves of course, but I've seen amazing results for landscape type stuff.)

It takes a little practice but it's not that tough if you have a tripod and any kind of software to help, and even with an 8mp camera, a composite image made of 2x2 or 3x3 images would give you a lot of resolution to work with compared to almost any single shot. A grid of 4 shots by 4 shots stitched into a 4' x 4' picture could have stunning detail even at that output size.
posted by mullicious at 7:25 AM on May 1, 2012

Contrary to what Yellow said above, you DO need to have a Costco membership for photo work. (Exceptions are food court and pharmacy.)
posted by turbogeezer at 7:39 AM on May 1, 2012

This article discusses what really happens at different DPI.

I like perfectposters.com. Even if you don't use them, they have a great series of articles on image size, paper type, etc.
posted by Mr.Know-it-some at 8:24 AM on May 1, 2012

W/r/t resolution, I would really, really get the recommendation of the vendor you choose.

Why? Well, many dpi calculations are based on half-tone screening; that is, breaking the different lightness and darkness values (of each ink, cmyk, for color) into a little dot that occupies a percentage of a cell in a matrix that makes up your picture. So when you start to have fewer pixels in than you have cells going out, you start to see square edges.

However, what with all the newfangled digital doodley-dads, images can be more easily screened stochastically; instead of a grid matrix, the values are "pseudo-randomized"! And "frequency modulated"! I have seen it work wonders for images whose input size were severely inadequate by halftone standards.

So the vendor themselves should have the best way for you to balance resolution vs. file size based on their postscript methods.
posted by Rube R. Nekker at 12:56 PM on May 1, 2012

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