What is Smart Zoom?
Smart zoom is not widely available. At the time of writing I am only aware of it being available in Sony digital cameras. Smart zoom works in a different way to digital zoom. It is cleverer and does not degrade the quality of the photo. The downside of this type of zoom is that you cannot use the full resolution of your camera when you are using Smart Zoom. For example if you have an 8 megapixel digital camera it only becomes available at 7 megapixels and below.
Increasing Smart Zoom
It is also true that as you decrease the resolution you are shooting at more Smart Zoom becomes available. Taking an 8 megapixel camera as an example again if you reduce the resolution to five megapixels 1.8x extra zoom becomes available. If you decrease the resolution down to 1 megapixel 4.7x Smart Zoom becomes available.
How Smart Zoom Works
This type of zoom works in a similar way to a photo editing package. If you have taken a high resolution picture and you do not like something towards the edge of the photo or you would like to highlight your subject more you can crop the outside of the picture. In other words you simply cut out the centre of the shot and throw away the remainder of the picture you no longer want. Smart Zoom is able to do this within the camera itself, before you take the shot.
This is the reason why you need to take the picture at a lower resolution. It gives the camera something to work with. So when you are taking a five megapixel photo with an eight megapixel camera it knows it is able to cut out and throw way up to three megapixels around the outside of the image. If you take a one megapixel image the Smart Zoom becomes even more powerful as it can cut away seven megapixels of the image if it needs to.
If you are considering printing your final image then you need to take care. For a 4x6" print you will need to make sure you use a resolution of 3 megapixels and higher.
In the first example standard optical zoom has been used to the maximum 3x. The picture was taken at the maximum resolution of 8 megapixels.
In the second picture the resolution has been cut to 5 megapixels and Smart Zoom is now available. This means that three megapixels around the edge have been cropped out by the camera. The maximum Smart Zoom available to use was 1.8x
In the third example the resolution was dropped to 1 megapixel. This allowed me to zoom right in with an extra 4.7x Smart Zoom.
The fourth example shows the first picture cropped using a photo editing package. This is the original 8 megapixel shot and I have used the package to cut away approximately seven megapixels worth of the picture. It is difficult to see from these pictures as they have been optimised for the web, but there is very little difference in quality between this picture and the one taken using Smart Zoom.
How do this compare to Digital Zoom?
Digital zoom works in a very similar way up to a point. It happily cuts away the outer sections of the image in the same way that Smart Zoom does. What is does next is attempt to restore the image to its full resolution. If we take the example above and consider the camera has chopped away three megapixels worth of information from the outer edge of a photo it then attempts to rebuild the lost three megapixels by adding them back to the remaining portion of the picture. It does this by guesswork. The guesswork is very intelligent, but nonetheless it cannot do this perfectly and this causes a decrease in the quality of the final image.
Further information on zoom: How Much Zoom Do You Need?