Quick Tutorial on Pixels, Resolution & Document Size

A lot of people, whether new to ImageConverter Plus or not, are confused by the some of the terms like pixel, pixel dimensions, resolution and document size.

The term "pixel" is actually short for "Picture Element." These small little dots are what make up the images on computer displays and in printed copies of images. The screen is divided up into a matrix of thousands or even millions of pixels. Typically, you cannot see the individual pixels, because they are so small. This is a good thing, because most people prefer to look at smooth, clear images rather than blocky, "pixelated" ones. The same term pixels applies to the dots used to print an image.

While the term pixel is used to describe both screen display and printed images, the rest of these terms refer to the PRINTED version of the photograph or image. They have nothing to do with the screen display.

Pixel Dimensions
What ImageConverter Plus is telling us is the width and height of our image in pixels. In other words, how many pixels are in our image from left to right and how many pixels are in our image from top to bottom. Let’s use an example where the photo has a width of 3456 pixels and a height of 2304 pixels. So another way of saying this is that it contains 3456 pixels from left to right and 2304 pixels from top to bottom. To find out exactly how many pixels in the entire photo you can multiply the width times the height, which in this case is 3456 x 2304, which gives a grand total of 7,962,624 pixels.

Lets link this up with your Digital Camera
We can assume that our sample photo was taken by an 8MP camera. The "MP" stands for "mega pixel", and "mega" means "million", so "8MP" means 8 million pixels. This means that when we take a photo with the digital camera, the photo will be made up of 8 million pixels (approximately, anyway – you have to round up from 7,962,624 to the closest million).

Let’s assume that in the example with the photo above the resolution (or horizontal resolution) is 72. What this is telling us is that when we go to print the photo, 72 pixels out of our 3456 pixels from left to right in our photo (the width), and 72 pixels out of our 2304 pixels from top to bottom in our photo (the height), will be printed for every one inch of paper. That’s what "resolution" means – how many of your image’s pixels left to right and how many of the pixels top to bottom will print in every inch of paper. (ImageConverter Plus lets you have a different horizontal and vertical resolution – but that is for an advanced story).

Document Size
The document size it the actual size the photograph will print at. In our example with pixel dimensions of 3456 x 2304 and resolution of 72 pixels per inch you wind up with a photo that is going to be 48 inches wide by 32 inches high. That’s a huge photo – but it’s not a problem because you can print smaller copies.

In fact, if you make the document size smaller than you will have more pixels per inch. So in our example you can print this photograph at any size smaller than 48 inches by 32 inches and get a higher resolution photo. If you make the size bigger than 48 by 32 inches, then the existing number of pixels will be stretched and you will have a lower resolution or fewer pixels per inch.

If you use online photo ordering sites they will often tell you "this photo can be printed at these sizes" and they are basing these recommendations on the pixel dimensions and resolution. They just do the calculations for you since this is a bit complicated!

Did you get all that? The best way to try this out is to experiment, change one number at a time and print – you have to print, none of this will impact the screen display. Go experiment and work towards becoming a graphics file master!

Author: David Silversmith