How do I make an image that scales when printed on a 3x4 foot poster?

Question

I am making an image to be printed on a 3x4 foot poster.

I am worried that the image will be pixelated after being printed. Should I use svg to make this poster? Is this even a valid concern?

Answer 1

You want your image to have the correct source resolution for the print. If your print resolution is going to be 300 dpi (dots per inch), then you should have your electronic doument in the same (or higher) resolution, that is, 300 ppi (pixels per inch).

For a 36×44 inch poster at 300 ppi, you need a 10800×14400 pixel source document. Photoshop can calculate this for you:

I wouldn't print a document with a resolution of less than 300 ppi, since most printers will also print at 300 dpi or higher. It's also the typical requirement print shops will give you. So, unless your source image has 10800 by 14400 pixels, then you might be able to see pixels in the printed document, because you (or, at a later stage, the printer driver) have to upscale it.

It depends on your source though: So, let's say you have a photo from a digital camera that is 1080 by 1440 pixels, then you have to upscale it by a factor of 10 to even get to the print resolution. Most upscaling algorithms will try to "blur" the image a bit*, so you don't get pixels, but rather a smooth transition. This however will make your result look a bit unsharp.

If your source is just text or graphics created in your graphics program directly (e.g. Photoshop), then you don't need to upscale anything and can work with the huge resolution right away.

Also note that the size of such an image is huge (raw 445 MB as you can see in the screenshot), and not all computers will easily handle such a high resolution.

_{* Actually, they will interpolate pixels, not blur it. See here: Image Scaling.}

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SVG graphics on the other hand are vector graphics. You can upscale vector graphics as much as you want, and it won't be pixelated when printed, simply because there are no pixels involved.

However, your source has to be a vector graphic too. You can't turn a photo into a vector graphic — simple graphics like logos and text however work fine, but you need to have them as a vector source already. Many companies or designers will provide sources as SVG or EPS files, which are vector-based.

And, as I mentioned before: Text and graphics created in Photoshop or similar programs are handled as vectors internally. Before you finally render your image, you can always change the dimensions of lines, squares, fonts, etc. (unless you specifically choose to "raster" them, which means turning the vectors into pixels).

Answer 2

slhck's answer covers this pretty well, so I'll just add a few things to that.

• As he mentioned, you can make a vector image any size you want with no degradation. Photo's can't be stored in vector formats, but simple graphics and text can. His answer talks about starting with a vector source file, which will provide the best quality if one is available.

  If you don't have a vector source file, images that are capable of being stored in a vector format can be converted to it. There are software and web services to do that. I've never used any, so I can't recommend a specific one, but a Google search will give you many options.

• If the image is of text, another option would be to run OCR on it to convert it back to text. Text characters are defined as vectors, so you can make the paper and font sizes as big as you want.

• Poster sized images often are viewed from farther away. If that's the case, you can get away with less resolution than 300 dpi, especially for a photo. Even 150 dpi often doesn't look too bad for a photo if you are at "poster size" viewing distance. YMMV

• If your image is a photo that already exists and you need to massively upsize it, you can often do it with better quality than the bicubic resampling used by software like Photoshop. There are a number of products that use fractal enlargement, like On1 Resize (previously Perfect Resize, and Genuine Fractals prior to that) and Alien Skin Blow Up, both commercial products with free trials, and Reshade, which is free.

  The quality of the results varies with the nature of the content and the quality of the source image. The fractal enlargement software I had experience with is no longer available, and I haven't used any of these products. But they appear to be the current big players.

• If you don't yet have the image and it will be a photo, you can create a source photo of the full, massive resolution needed for a high-resolution poster size using the "gigapixel" approach. In this technique, you take a series of overlapping images, each a small piece of the total. Then you use panorama software to stitch the pieces together into the total image. There are endless software offerings to do this on every computer platform, and lots of online tutorials and product reviews.

Answer 3

well you could try some ai image software that can "look" at your image and turn it into a vector equivalent that will scale. Evidently some guys in the UK figured out how to do it for video, including preserving shading, so it is probably doable for stills.

Another method I read about says increase your pic with bicubic resampling by a bunch of 110% increments and the pic won't get grainy. here is the link

http://www.peachpit.com/articles/article.aspx?p=420909&seqNum=12