Clients frequently need to send us photos, or to pick photos as from iStockPhoto for us to use.
An issue that comes up is whether the picture is large enough for what we are going to use it for? Or how large does an image need to be for the web, print, or for a trade show display or billboard.
Here’s a short rundown. First of all, this applies mainly to photographic images. Logos and illustrations are normally in “vector” format where size doesn’t usually matter.
Photo image sizes are in terms of “pixels” which is one little dot of a particular color, that the image is built up from.
The first thing you need to know is that different resolutions – pixels (px) per inch , or dots per inch (dpi) – are required for different applications. For the web, it is 72 dpi. Of course that depends on the screen size but if you are working on a website that is 1000 pixels (px) wide, that is the largest an image file could possibly need to be.
For most print applications it is 300dpi. That includes everything from postcards to letterhead to magazine ads.
For large format printing such as trade show displays or billboards, it is usually 100 to 150dpi.
The formula then for how large an image needs to be is the required dpi times the size in inches.
Both height and width need to be considered. So the orientation (portrait versus landscape) comes into play.
So, for an image to be used on an 11 by 6 inch postcard, the maximum image size needed would be 11×300 by 6×300 or 3300 by 1800 pixels.
In choosing an image you need to consider if it will be used ONLY on the web. If it is also going to be used in print, it needs to be large enough to be used in that situation as well.
We always prefer the original, unedited image file. Any sort of editing usually reduces the amount of detail. And often, a picture needs to be cropped (a piece of it cut out for use) so that requires a larger file to start with. We do have tools that can artificially increase a picture size and sharpen it up – but there are limits.
Hope that helps clear up this subject.
Picture Sizes
