Digital Cameras - Setting the Image Size
By: Colin Aiken

Setting the size of an image is something specific to digital cameras, it just didn't exist on film cameras. One effect of changing the size of image your camera captures is that it also affects the size of the digital image file your camera stores on its memory card and therefore the number of pictures you can store on any given size of card.

This is size in terms of computer memory or storage and is expressed in kilobytes, megabytes and gigabytes. Digital cameras, like all other digital devices, produce digital files that need a certain amount of space to store them. The image size setting on your camera will significantly affect the size of the resultant image file.

It may be easier to think in terms of how many pictures it will take to fill up your memory card. You will get the maximum number of pictures if the image size is at it's lowest setting. By the same token, you will get the minimum number of pictures when this is at it's highest setting.

In practice, this means that if getting as many pictures as possible on your card is the most important thing to you, then you need to adjust the image size to the minimum available setting.

Image size has always been an important aspect of cameras even before they became digital. With film cameras it was controlled by the size of the film that the camera would accept. A 35 millimetre camera was called that because that was the size of film it used. If you wanted larger images, you needed a camera that would accept larger film. These were called medium or large format cameras.

When digital cameras came along the idea of being able to take different sizes of image with the same camera became possible. This is simply done by changing the image size setting in your camera. It is perfectly feasible to change the image size between shots and store different sizes of image on the same card.

One thing that hasn't changed is the effect of using a larger or smaller size of image whether it's a digital image or the size of the negative you got from a film camera. A bigger image (or negative or transparency) will produce a better image. Most adverts for cameras or other sources of information about digital photography will tell you just that, but it's not the whole story.

The first thing to consider is what exactly is meant by a "better image". Things like the accurate reproduction of colour, the image noise produced by the camera or the amount of distortion produced by the lens are entirely unaffected by image size but play a large part in deciding if one picture is technically better than another. It is certainly the case that two different cameras can produce the same size of image but with very different overall technical quality.

That is something to think about when looking to purchase a new camera but it's not under consideration here because this is just about the effect of altering the size setting on your camera. The only thing that changes when you do this is the "resolution" of the images your camera produces.

What is resolution?

The word resolution means the ability to see (or resolve) fine detail in a printed photograph. A high resolution image will have a lot more visible detail than a low resolution image. The image size setting on your camera may even be called resolution because they are so directly related. A large image means high resolution and a small image means low resolution.

Please note that this ability to resolve fine detail only applies when you print your digital photograph and not when you are viewing it on a computer monitor. Viewing a high resolution picture on screen will allow you to zoom in and look at the detail you have captured, but that's it. When you zoom out to see the whole picture then the resolution of the image you see will be that of the screen itself, it physically cannot be any higher than that.

You can prove this for yourself by simply comparing a high and low resolution image side by side on your computer. As long as they are visibly the same size on screen, they will have the same resolution. No matter how close you get to the screen, you will not see any more detail in the larger, high resolution picture.

In practice this means that if you only ever view your digital images on a computer and never print them then you can use your camera's smallest image size setting and gain the benefit of being able to store lots more pictures on your memory card.

On the other hand, if you want to make big prints from your camera's pictures, then you should set the image size to the largest you have available. Another thing you can do with a large image is to print (or view) only a small part of it. This is sometimes called "cropping". So, if you think you might want to do this at any time then you should set your image size or resolution to its maximum.

The size of a digital image is measured in megapixels, which simply means one million pixels. A pixel is the smallest part of a digital image and is a single colour. If you zoom in close enough to any digital image, you can see the individual pixels that it is made of, all neatly lined up in rows and columns.

You might have noticed that, so far, I have not made any mention of the actual numbers involved. Whereas, every reference to a digital camera you come across will usually include mention of the number of megapixels it has. This is an indication of the maximum size of image that the camera can produce.

The actual size of the image only matters when it comes to comparing cameras but, here is an indication of how megapixels relate to resolution and print sizes. A high resolution print at 6 x 4 inches requires just over 2 megapixels. An A4 print (roughly 8 x 11 inches) at the same resolution needs an 8 megapixel image.

The situation is complicated by the fact that it is easy to resize a digital image after it has been taken. This is called "interpolation" and some editing programs (and even some printers) can do it very well. So well in fact, that they can fool the eye into thinking that your picture has more resolution than is actually there. Added to that is the fact that the human eye has an upper limit to the detail it can resolve.

You could print an 8 megapixel image at 6 x 4 inches and although technically it would be at a much higher resolution than the 2 megapixel version, no human in the world has good enough eyesight to tell. You also have to take into account that large pictures tend to be viewed from further away than small ones, which greatly affects how much detail people can actually see. All in all, the whole issue of image size and resolution is at least partly a matter of personal taste.

When it comes to setting up your camera however, it doesn't matter what the actual largest size is, just that it's the largest available from your camera. You should use this setting if you ever want to make big prints or do further editing work like cropping and printing just a part of the picture.

If you have never checked the size setting on your camera, I definitely recommend that you do so. Most cameras will give you a choice of either small, medium or large for the size and, when they first come out the factory, they are usually set to medium. I'm sure the manufacturers' figure that this is a good compromise setting for most people but personally, I think that it's the setting that is least likely to be right for most people.

For example, if you have an 8 megapixel camera, then a medium setting is likely to be around 4 megapixels. This is too big to view on screen without shrinking it down and, if this is the only way you want to see your pictures, it is quite wasteful of space on your memory card and hard drive. In these cases you should use the minimum size unless that looks too small on screen (you may have a very big screen).

The other side of the coin is that, if you have spent your hard earned money on an 8 megapixel camera because you want to print big, high quality pictures or do some photo editing then, unless you have the image size set to maximum, you wont be taking 8 megapixel pictures. You could have saved your money and just bought a 4 megapixel camera.

So in conclusion, go and check the size setting on your digital camera, you want the minimum size for viewing and email and the largest size for big prints or editing. Medium is usually not much use to anyone. Let's not compromise!

About the Author
Colin Aiken is a professional photographer based in the United Kingdom. You can view his photographs and get more tips at: http://www.lovethepictures.co.uk.