Optical Zoom Digital Camera

Optical vs. Digital Zoom

More and more camera manufacturers are choosing to label their digital cameras with the total (optical x digital) zoom. This is an unfortunate development and only serves to confuse consumers.

Most people who have used a 35mm camera or an APS camera are aware of only optical zoom. Optical zoom uses the optics (lens) of the camera to bring the subject closer. Digital zoom is an invention of digital video cameras. It is not uncommon to see digital videocams with 300x digital zoom.

For our purpose, digital zoom is not really zoom, in the strictest definition of the term. What digital zoom does is enlarge a portion of the image, thus 'simulating' optical zoom. In other words, the camera crops a portion of the image and then enlarges it back to size. In so doing, you lose image quality. If you've been regularly using digital zoom and wondered why your pictures did not look that great, now you know.

Is digital zoom therefore all bad? No, not at all. It's a feature that you might want in your digital camera (in fact, all digital cameras include some digital zoom, so you can't really avoid it), especially if you don't care about using (or don't know how to use) an image editing software. So, as far as digital zoom is concerned, you can do it in camera or you can do it afterwards in an image editing software. Any cropping and enlarging can be done in an image editing software, such as Photoshop.

So, when a digital camera is advertised with 3x digital zoom, no big deal. You can achieve the same 3x (and in fact as much as you want) digital zoom effect in an image editing software. The advantage of doing it later is that you can then decide exactly which portion to crop and how much to enlarge (3x, 4x, ...). If you do it in camera, image quality is irreversibly lost.

Someone in a digital camera forum once mentioned that he uses digital zoom because it might mean the difference between capturing a great shot or not at all. Umm, let's think about this a bit. True, if by zooming digitally in camera you get to see what your subject is doing and thus can capture the shot at the right moment. Not quite true, if it's something like a landscape shot, and the mountains ain't going nowhere fast, because you can achieve the same cropping and enlarging effect after the fact in your image editing software. So, it's really up to you, if you know what you're doing.

What, therefore is the rule of thumb, when it comes to using zoom? Here it is: Always use optical zoom. When buying a camera, choose one that warns you that you are about to use digital zoom or that allows you to disable digital zoom (most do). If you do use digital zoom, use it only if it does not appreciably impact your image quality. If you rarely print past 4x6 in. photos, digital zoom may not adversely affect you.

When comparing cameras, you should always use optical zoom. There is no point in comparing digital zoom with digital zoom or optical zoom with total zoom. Always compare optical zoom with optical zoom.

Optical Zoom vs. Resolution

What about optical zoom vs. resolution? Sigh! Now y'all know that we cannot and should not be comparing apples 'n oranges, but we still try. The question I often read about goes something like this: "Which is better: 2 megapixels resolution with 3x optical zoom or 3 megapixels resolution with 2x optical zoom?"

The megapixels resolution of a digital camera can be thought of as the number of pixels available to capture an image. With a 2 megapixels camera, you have 2 million pixels to record an image. With a 3 megapixels camera, you have 1 million extra pixels to record the same image -- in other words, you are able to capture the image in more detail.

Whether you zoom or not does not affect how many pixels are used to capture the image. So, zoomed at its maximum, a 2 megapixels 3x optical zoom digital camera will still have captured a 2 million pixels image. Likewise, a 3 megapixels 2x optical zoom digital camera will always capture a 3 million pixels image.

The real question behind the question is, "So now if I use digital zoom to zoom in with the 3 megapixels camera and simulate a total zoom of 3x, will the resultant image quality be less, the same, or still better than the one I captured with the 2 megapixels 3x optical zoom camera?" You follow so far?

With a 2 megapixels digital camera, you can make good 4x6 in. prints, and maybe even 5x7 in. prints. With a 3 megapixels digital camera, you can make good 8x10 in. prints. So, as far as image quality is concerned, the 3 megapixels camera is better. Unless you are always going to take pictures at max. zoom, the 3MP camera is better because at 2x optical zoom and less, it is always capturing images with more detail than the 2MP camera.

What we are really trying to say is this: do not compare. You've got to decide what is more important to you: resolution or optical zoom? If the answer is both, then find a digital camera that has both. It's that simple. If it's outside your pocketbook range, then choose a digital camera for what is more important to you.

To repeat, we do not compare optical zoom with megapixel resolution because optical zoom is not megapixel resolution-dependent. That is, the resolution of your final image does not change no matter how much you zoom in. If your digital camera is 5MP and has a 12x optical zoom lens with focal length of, say, 30-360mm, then at 30mm, your image is 5MP and at 360mm, it is still 5MP. With digital zoom/enlargement, the megapixel resolution decreases as you "zoom" in digitally (the premise behind Smart Zoom from Sony and Safe Zoom from Canon, see below); if you try to bring the cropped image back to the same 5MP size, then there is pixels interpolation and the resulting image suffers in quality.

We always disable digital zoom in camera, choosing to do our own cropping and enlarging in an image editing software.

Optical vs. digital zoom? There is no contest. Only optical zoom matters when selecting a digital camera.

Smart Zoom

Recently, a new type of digital zoom has appeared on the market, pioneered by Sony, called "Smart Zoom." Smart Zoom can be viewed as an "ethical" digital zoom which avoids interpolating the image and so avoid degrading image quality. Smart Zoom works only if you select an image size smaller than the full available image size. So, for example, if your digital camera is capable of producing a 5MP image, Smart Zoom is available only if you select to save your images as 4MP or less. In other words, with this particular type of digital zoom, the MP resolution decreases as you 'zoom' -- in other words you are just cropping the center of the image (without interpolating back to the original resolution).

Say, your digital camera is 5MP and you select to save your images as 3MP. So, in effect, you are forfeiting 2MP of image data (extracted from all over the image area) that the digital camera's sensor has captured and now has to throw away [you hope the camera makes the right decision and does not throw away important image data]. Enter Smart Zoom that says, "Hey, instead of throwing away 2MP of good data from all over the image area, why don't I crop out all the pixels starting from the outside perimeter? When I've cropped out 2MP of image data all around, I have 3MP left over and that's what you want, right?" Notice, the 3MP image does not have to be interpolated and enlarged back to 5MP as traditional digital zoom does (because you elected to save it as 3MP, remember?). So, in effect, you've basically more or less retained the same image quality but you have to save your resulting simulated zoomed image in a smaller image size. Of course, if now you turn around and enlarge it in post-processing, you will be limited to what a 3MP image can be enlarged up to without image degradation.

I call Smart Zoom "ethical digital zoom" because it is not made available at full image size -- this would cause image degradation. The smaller you elect to save your image, the more smart zoom power you have available (folks, you're basically just cropping the image without re-enlarging, which you can also do at any time in post-processing). I would personally not recommend cropping down below 3MP, which means that Smart Zoom is useful only in digital cameras with 4MP and above.

So, our recommendation still holds. If you want zoom power, only optical zoom matters! Smart Zoom is the better form of digital zoom, but what you gain in simulated zoom power (again, you're just cropping), you lose in image size. There's no free lunch.

Again, don't buy a digital camera based on digital (traditional or smart) zoom. Always compare optical zoom with optical zoom. If you are comparing 2 digital cameras with the same optical zoom, but one has smart digital zoom and the other has traditional digital zoom, then the smart zoom has a slight advantage. But personally, I wouldn't even look at that because there are a lot more important features to differentiate the cameras.

source: photoxels.com

Digital Camera Zoom

Digital Camera Lenses

Point-and-shoot zoom lenses
Most point-and-shoots today have zoom lenses, which are labeled in a couple of different ways. Sometimes you’ll see them both: For example, “3x optical” and “28mm-84mm film equivalent.” Both mean essentially the same thing, except that the latter figure is telling you what the zoom range would look like if you were looking through a film SLR camera. The technical reason is that the numbers on the zoom lens might actually be something like 8mm-27mm. But most people are more accustomed to understanding how lenses look on an old film SLR camera. So, we know that a 50mm lens on a film camera is more or less our normal field of vision. Anything higher, such as a 200mm lens, is considered a telephoto lens. And anything lower, such as a 24mm lens, is considered a wide-angle lens. So most manufacturers will include the terms “film SLR equivalent zoom” or “35mm equivalent.”

You might also sometimes see the term “digital zoom” in a point-and-shoot camera. Digital zoom works by cropping in on a portion of the image from the camera’s image sensor and magnifying it, or sometimes, interpolating it. When you use digital zoom, it always degrades the quality of the image. CR’s Take: Whenever you buy a digital camera, be sure to turn off the digital zoom in your camera’s menu.

SLR lenses
In our tests of SLR lenses, performance varied widely and bore no relation to price. Here are some considerations before you buy:

Assess your existing lens. If you already own an SLR, one of the rated zooms might be a step up from your lens. Among lower-priced zoom lenses, wide-angle models might offer better image quality than those that are more oriented toward telephoto (i.e. 200mm or 300mm).

Consider a wider zoom range. Most SLRs are bundled with a wide-angle zoom kit lens similar to those in the Ratings. But you can buy the body alone or together with a different, more versatile lens. If you think you might someday need a greater range than the standard kit lens offers, and your budget permits, buy the camera body bundled with a full-range zoom instead. You’ll dramatically expand your shooting options and what you save on the kit lens will partly offset the bigger lens’s higher cost.

Investigate camera compatibility. Different lenses mount to different brands of camera. Some utilize the four-thirds system, a universal mount used on some Olympus and Panasonic models, instead.

Look for non-zoom lenses. Those with a fixed focal length generally have higher image quality and light sensitivity than comparably priced zooms.

source: consumerreports.org

Camera Digital Zoom

Is it better to use in-camera digital zoom or crop and resample with software?
By. Sue Chastain

Question: Is it better to use in-camera digital zoom or crop and resample with software?

Answer: Do me a favor. If your digital camera offers a digital zoom option, go get your camera right now and turn this option off! Don't use it... ever!

Digital zoom does not capture any additional detail than the maximum optical zoom of your camera. Instead it uses interpolation to make a portion of the image larger by adding extra pixels. Just as your photo-editing software does when you resample, the camera has to "guess" at how the new pixels should be added to give the illusion of increased detail. But detail that was never there to begin with cannot be recreated.

Now you may be thinking, "If it's the same as using software to resample, I'll save myself the extra step and go ahead and use digital zoom."

Not so fast!

Whether you are using optical or digital zoom, the closer you zoom in on a subject, the harder it is to get correct focus and exposure. Also, problems created by camera shake are intensified. So an image that is captured with digital zoom is more likely to turn out worse than one captured at maximum optical zoom then cropped and resampled in your photo editing software. If you still don't believe me, go take some test shots and compare.

Another advantage of using photo editing software to resample is that many software programs have a variety of resampling algorithms to choose from. Some methods can give better results than others depending on the subject matter of the photo.

A higher megapixel camera will give you more freedom to crop and still get good quality prints, but if you really like to shoot close-ups, you should invest in higher optical zoom or a telephoto add-on lens.

Camera Zoom

Zoom Lenses for Digital Cameras

You should be aware though that one 3x zoom digital camera can offer a different amount of zoom to another camera that is also described as having 3x zoom.

All cameras have something called a focal length. This is true even for a camera without a zoom lens. The focal length is the distance from the optical center of the lens to the camera's focal point. For digital cameras the focal point is located on the camera's sensor. For a camera without a zoom lens the focal length is said to be fixed as the lens never changes position. When using a zoom lens the position of the lens changes as you zoom in and out. As you zoom in the focal length increases. As you zoom out the focal length decreases. Therefore the focal length of a camera with a zoom lens is given as a range of two figures. The 105mm is the focal length when the zoom is fully extended.

By dividing the longer focal length (105mm) by the shorter one (35mm) we can work out that this camera has a 3x zoom lens.

Cameras offering a wider picture angles are said to have a wide angle lens. The camera with the focal length mentioned earlier of 35 - 105mm can zoom in closer even though both cameras have a 3x zoom lens.

The Nikon Coolpix 5400 is considered a wide angle digital camera. Its focal length ranges from 28-116mm. It is normal to see two zoom ratios quoted for a camera. One is for optical zoom already discussed the second is for digital zoom. Digital zoom is completely different to optical zoom. Rather than using the lens to zoom, digital zoom is carried out by software inside the camera. For example a camera with 10x optical zoom and a 4x digital zoom can give a combined total of 40x zoom.

Check out my other guide on nikon digital camera
summarized from cameras.co.uk