One of the most misunderstood concepts that digital photographers have to deal with is the concept of resolution. The question that I am most asked, not just by folk’s new to digital photography, but by those that have been snapping digitally for some time is “How do I understand resolution?” Although resolution is a word that is used in a number of aspects of digital photography the one that most of us are concerned with relates to the size of an image in pixels. Pixels, as we know, are the little squares that we see when we enlarge our images using our image editing software. They are the building blocks of your images in a similar way that grain makes up your images in conventional photography.
The size of the image can be stated using either a blanket term such as 6 million pixels, or you may see it as 6 mega pixels. The other way given is as the dimensions of an image e.g. 1280 pixels x 960 pixels. Still confused? The important thing to remember is that pixels and resolution determine what size and quality you can display and print your images.
When you bought your digital camera you would be told that it would capture images at a certain resolution i.e. with a certain number of pixels. The importance of how many pixels your camera needs depends upon what you are going to use it for. If the camera is to be used for taking photographs that will solely be shown on line a very low resolution can be used. If you wish to print your pictures, as most of us do, then in general the higher the pixel count the better.
The traditional display for the web is 72 ppi (pixels per inch), whilst for printed images 300 ppi is the standard used for maximum quality. What this means is that in each linear inch of your printed picture there will be 300 pixels. The size of your printed photograph will be the pixel dimensions divided by 300. So if your camera is capable of 8 million overall pixels that would give dimensions of 3264 x 2448. Divide by 300 will give a photograph of approximately 11 x 8 inches.
To help determine the size of your photographs printed at 300ppi the following should help.
OVERALL PIXELS DIMENTIONS IN PIXELS PRINT SIZE AT 300 PPI
8 million 3264 x 2448 11 x 8
5 million 2592 x 1944 8 x 6
3 million 2048 x 1536 7 x 5
1 million 1280 x 960 4 x 3