Well, we are deep into the holiday season and we have a few customers stopping by the shop to get postcards and greeting cards printed to send to family and friends for the holiday. These are always fun jobs and a welcome break from more usual business cards, letterhead and stationery. Some of the cards we print are just graphics and text, but there are also many involving photographic images.
Although, this can raise some problems when a specific photograph is unusable due to resolution. How disappointing. But if you are preparing to print a card with a photograph, then what resolution should you use? And what does that even mean?
Today we will take a look at a few basic ideas related to resolution for printing.
1. DPI & PPI
If you are used to printing at home, then its very likely that you have encountered the term DPI, or dots per inch. This is a measure of resolution for printers, whereas PPI is a measure for your camera or other optical device (like a scanner). There is more detail to that of course, but simply put, both are a measure of the number of pixels in a given image. If an image has a DPI resolution of 72, then there are 72 pixels in each square inch of the image. Likewise an image with a 300 DPI would have 300 pixels in a square inch.
These numbers are significant because they help determine the size at which an image can be printed and look good. Most images on the web (or designed to be viewed on-screen) have a resolution of 72 dpi. This looks great on screen, and can be made into a nice small file to use on a web site. But it won’t look so well once it is printed.
2. 300 is the Standard
For most purposes in printing at home and printing commercially, 300 dpi is the standard for printing images. There are many cases in commercial printing when we need even better resolution, but as a general rule printing at 300 DPI will make an image will look great.
If you took your picture with a decent digital camera you should have no problem getting an image with a proper resolution of 300 dpi.
3. Bigger is Better
So you have an image that has a 72 dpi image resolution, and on your screen it looks big and detailed, but when you print it something is lost. Actually, a whole lot is lost, because it comes out blurry, grainy, and there is nothing about it that you like. What happened?
Well, here we have to look at the pixel size of your image. If you took a picture on the smallest setting on your camera, then you might end up with an image that is 640 Pixels by 480 pixels. If we divide those dimensions by 72 (our DPI) than we can get an idea of size. So, 640/72= 9 Inches (roughly) and 480/72= 6 and half inches. That sounds great, until you remember #2 above. These sizes are for a monitor/screen, for print we need to divide by 300 DPI to ensure quality. So, divided by 640/300= 2.125 inches and 480/300= 1.6 inches. This means that we could make a decent print of this image if we reduce the size to 2.125 by 1.6 inches, but any larger and in an inverse proportion your satisfaction with the print will diminish.
In some instances, a small picture could be just fine for your card. It depends on the size you want it to be. But, a usual greeting card might be 5 inches by 7 inches and if you want to fill the front of the card with a photograph, what pixel size will you need?
All we have to do is to reverse the math. 300(dpi) x 5 inches = 1,500 and 300×7= 2100. So we would need an image that was 1500 pixels by 2100 in order to fill the card. This is usually the fine or superfine setting on many digital cameras.
But, of course, we want our card to look the best it can, and so a general rule of thumb is the bigger the better.
So, there are a few details that should help you get your images ready to print. Of course, preparing images for print is a full-time job for some folks, so if you have any more questions, or would like to know more, just ask below. And as always feel free to stop by the store. We are in the Justa Farm Shopping Center right in Huntingdon Valley.
