Myth of Mega Pixels

The word itself simply means a million pixels and a pixel is the smallest individual part of a digital image. If you have some viewing software that allows you to zoom right in to an image then you can see them for yourself – they just look like different coloured squares. You might recognise the “pixellated” effect used on TV to obscure peoples faces.

Every digital image (including the screen you are looking at now) consists of a rectangular array of pixels, the more is has, the bigger the image. If you look at the display settings on your computer, you can find the number of pixels in the screen image you are viewing right now. This should tell you the horizontal and vertical number of pixels. Multiply these two numbers together to find the total number of pixels.

A very common screen size is 1024 (horizontal) x 768 (vertical) pixels. Multiply these numbers together and you get 786,432 pixels in total. In terms of mega pixels, that’s less than 0.8MP. So, if you are looking at an image from your 10MP camera on a screen that is only showing you 0.8MP, where have all the other pixels gone?

In truth they have just been lost. The fact is that you cannot see any more pixels than exist for the size of the screen on which you are viewing them. In order to see an entire 10MP image your viewing software has to “lose” 90% of the pixels. If it didn’t, you would only see a small part of the image at one time and you would have to scroll around to see the rest of it. This is exactly what happens when you get a large image in an email or a website.

The number of pixels or mega pixels in an image is often called the “resolution” of the image and the more you have, the higher the resolution your picture will be. Resolution means the ability to see fine detail in the image so you should expect that a 10MP image would show a lot more fine detail than, for example, a 1MP image. But does it?

Well, if you are looking at the whole of your digital image on screen, the simple answer is – no!

You don’t have to take my word for it, you can see this for yourself if you have software that allows you to resize an image as well as zoom in or out. If you take a large image, make a copy of it and then reduce it in size to something around the size of your screen, you can then compare a high and low resolution version of the picture side by side.

When you make an image smaller you are, of course, lowering the number of pixels in it and therefore, its resolution. This is also what happens when your viewing software zooms out to fit a large (high resolution) picture on your screen. The difference being that the zooming process has no effect on the digital file itself.

When you compare a high resolution image that has been zoomed out to fit the screen with a low resolution one that is the same visual size without zooming, you will find the level of detail in both to be identical. It cannot be any other way. The maximum resolution you can ever see on screen is that of the screen itself. There may be much more resolution in the original image but you cannot see it and look at the whole image at the same time.

The fact is that of the millions of digital pictures taken each day, very few are ever printed. Most are simply viewed on computer screens and stored somewhere for later viewing. Whilst there is absolutely nothing wrong with that if you are one those people who never print digital pictures, then the myth of mega pixels applies to you especially.

If you are looking for a new camera, you will probably not find anything with less than about 4MP, rising up to about 12MP. As we have seen however, both these cameras effectively have exactly the same resolution if you are just viewing the whole image on screen.

What is more, the 12MP image will take up more space on your memory card (so it will hold fewer pictures) and you will need to resize it for sending by email or posting on a web page. It will also take much longer to send by email and view on a web page.

Even if you have a high resolution, large mega pixel camera that does not mean that you are stuck only taking large pictures. Digital cameras can take pictures at different resolutions and you simply need to find your settings menu to make this happen. The setting may be called resolution or size. Depending on the camera, you may have numbers or just high/medium/low as your choices. Setting the value to the smallest number or low will give you images that are much better suited to viewing on screen.