 BetterPhoto Member |
Digital vs. Optical Zoom What is the difference between a digital and optical zoom? I have a Nikon 5700 Coolpix and never even thought about there being a difference (duh...). Thanks for whatever explanation you can give (in everyday speak-ease, please).
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Jon Close |
Optical zoom refers to the lens physically changing the focal length. At all zoom settings the lens projects an image on the full digital sensor. Digital zoom crops the image from the center of the sensor and enlarges it. There is less detail in the digital zoom image, since it is created using only a portion of the pixels available on the sensor.
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Miltos Vasiliadis |
Optical zoom - zoom made by the lens. This means real zoom. The same happens if you move closer to the subject. Pros: You get a very good image detail. Cons: Depending on the lens quality, you may have aberrations ("mistakes") in the image. It gets flattened, the lines become less straight, etc. Digital zoom - A re-creation of the image by multiplying PART of its pixels. It is virtual, because the human eye or brain cannot do that. Pros: You don't need super-expensive lenses to do it. Cons: Less detail, loss of reality. What do I mean? Well, I've argued many times about this; if you digitally zoom a subject, it doesn't change apart from getting enlarged. Think of it this way: Look at something - a flower, for example - and then step 1 meter closer; aren't there other things that change apart from its size? The human eye aberrates, and the lens does that too. Digitally zooming a picture is like looking at THE PRINT through a magnifying glass, while optically zooming an image is like looking at THE SUBJECT through a magnifying glass. This is my opinion, although nobody asked for it ... sorry :)
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Robert Korb |
Digital images are represented by many colored dots or pixels. The number of pixels used to represent the image depends on the resolution you set on your camera, and the capacity of the camera. For example - The highest resolution you would find on a typical 2 Megapixel camera would be something like 1600 pixels horizontally by 1200 pixels vertically (of course horizontal and vertical can be changed by rotating the camera when you take the picture). [You lower the resolution if you want to increase the number of images you can store on your memory card] So that's how the image is STORED.. But how is it DISPLAYED?? Well a typical computer monitor has a resolution of 1024 x 768 pixels it can display. Now thats less than the 1600 x 1200 your 2MP camera can take. As a result, you cannot see every pixel of your image in your computer display at one time. You can only see the 1024 x 768 portion of your larger image... unless some clever stuff is done. The clever stuff is that the computer software averages out neighboring pixels and makes a "best guess" as to the color of 1 pixel to represent more than 1. In other words, it can shrink the entire image by taking away (for example) 4 pixels and representing it as 1 pixel that is the average in color, of the 4. Since the entire image is smaller it fits on the display. Your camera does this too - especially since the displays on digital cameras are so much smaller than computer displays. But the original pixels STORED on the image don't change - They are just changed for the purpose of display. So what does this have to do with digital zoom? Let's say you have a really high power digicam - 10,000 pixels by 10,000. Then the overall dot for dot image could take up a large area of your livingroom floor. If you get up on a ladder you see the whole thing. But if you put your nose down to the floor you only see a few inches of the image. That's digital zoom. The image quality is unchanged. There is not a bit more detail in the image than when you looked from the ladder. But when you get closer to the floor you do see things you didn't notice up there...Because you're taking a closer look. Now lets say you look through a magnifying glass. You no longer can see what the image is! Rather you just see dots of different colors. Not too good is it. As I said - the resolution of the image doesn't change..it's just your VIEW of it that changes. Now optical resolution is different. It depends on the quality and capability of the lenses on your camera. An optical zoom does change the resolution of your image. It also changes how much of the image is visible. You see less of the field, but the part of the field you see is closer and truly has more detail and THAT detail will be recorded in the pixels of your digital image. That's why optical zoom is generally preferred over digital zoom. BTW - the zoom part is actually the ability to change the magnification "infinitely variable" from one extreme to another (say 1x to 10x) But the what is really meant in the preceding discussion is magnification of the image, not really the zoom part, because after all, we are taking STILL images not moving ones... RL Korb
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