Digital zoom verses Optical zoom

When looking at camera advertizements particularly point and shoot cameras. You can't help but notice how much digital zoom these cameras are capable of, and perhaps you are wondering what the difference is between digital zoom and optical zoom. In this article I will explain why optical zoom is far more valuable than digital zoom and if your camera has a digital zoom feature why you might want to turn it off.

The zoom function

Most modern cameras have a zoom function some have optical zoom and others have digital zoom and many cameras have a combination of the two. Zoom is the cameras ability to change the size at which an object appears on the viewfinder without having to get closer or further away from the object.

How digital zoom works

The process of digital zoom is best described by example. I have chosen a scene of walnuts for my demonstration. We will be zooming in on this image using only digital zoom.





The red border represents the area we will be zooming in on. In the first step of digital zooming the camera crops the image along the red border. This is the same process as if you where to crop a image in Gimp or Photoshop except that the camera does the whole process automatically on the fly Without you having to know how it works.





After the image has been cropped its surface area is about 14.5 times smaller which means it has about 14.5 times viewer pixels than the original image had before it was cropped. If you where using a 12 megapixel camera less than one megapixel would remain in the cropped image.





but as you know the camera does not give you a tiny image. It enlarges the image. If we where to enlarge the image to the same size as it was before it was cropped, all the pixels of this small area would become enlarged and easily visible to the naked eye.





The camera cant present you with a tiny image and it would look horrible if it presented you with simply a pixelated enlarged version of this tiny image as you have just seen. So here comes the final step of the digital zooming process. The cropped image has only a small amount of remaining pixels and in order to make the image larger the camera has to generate new pixels via a process called interpolation. Interpolation is an algorithm that analyzes existing pixels and then generates new pixels that get placed between existing pixels. The algorithm attempts to generate pixels that create a smooth transition between existing pixels. The resulting image looks a lot better than simply enlarging the image but it is far from perfect and lacks definition and detail.

How optical zoom works

Optica lzoom has been around a lot longer than digital zoom and does not require any digital manipulation. I will now demonstrate a optical zoom using the same walnut scene.





just like before the red border represents the area we are going to zoom in on except this time we will be using optical zoom.





Unlike digital zoom optical zoom does not require any cropping and resizing of the image in fact optical zoom does not require any digital processes of any sort. When using optical zoom the object gets enlarged optically by the lens before it gets projected on to the cameras sensor in much the same way a telescope will make a distant object like the moon larger before it gets projected on to the retina of your eye. Because the image dose not need to be cropped all of the cameras pixels are utilized in creating a much clear and sharper image.

Digital zoom vs Optical zoom side by side comparison

The image below shows a side by side comparison between digital zoom on the left side and optical zoom on the right side. When compared side by side it couldn't be any more obvious that optical zoom is far superior to digital zoom

Digital zoom	Optical zoom

The truth about digital zoom

Professional cameras do not normally have a digital zoom feature. Digital zoom is a feature found on consumer type point and shoot cameras as well as camcorders in fact everything you have learned in this article applies to camcorders in the same way it applies to still cameras. Consumer type cameras get bought by consumers who are not usually technically educated enough to understand that there is no value in a digital zoom feature. Digital zoom has bean heavily used in advertizing and cameras have bean getting increasingly large digital zoom capabilities. Think about it when was the last time you saw a consumer camera advert with big bold letters 100 x Digital zoom it has become almost like a race between camera manufacturers to build cameras with increasingly large digital zoom capabilities which then get used in advertizing in order to make their camera appear superior over their competitors in the eyes of the uneducated consumer. All these cameras are doing is cropping a increasingly larger portion of the image and then interpolating it in order to generate non existing pixels to make the image larger

What to look for if you need a Camera with lots of zoom

When buying a consumer camera and you need a camera with lots of zoom here is what you should do. There are of course many things that you should look for when choosing a camera, but everything else being equal choose the camera with the best optical zoom and completely disregard any digital zoom feature that cameras might have. Some lenses will have better quality optical zoom than others but but all of them will be superior to digital zoom on any day of the week. If your camera does have a digital zoom feature you might want to consider disabling this feature. Refer to your cameras manual to find out how. This way you will not accidentally degrade your image by zooming in beyond the cameras optical capability. If further zooming is required you can crop the image later using your favorite image editing software.

When and why use digital zoom

Now that you fully understand all about digital zoom you can make a educated decision as to wedder you want to use your digital zoom feature or not. One reason some people might decide to use their cameras digital zoom feature is if they don't really know how to use image editing programs on their computer or simply cant be bothered with them. In this case the digital zoom feature will do all the work for them. But do remember to get a better image you are better of getting closer to your subject as opposed to zooming in on it using digital zoom