How does digital zoom differ from optical zoom?

Answer 1

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.

Answer 2

There are two types of zoom on a video camera — digital zoom and optical zoom. A camera can have either or both types. The two different types are very different and the unwary buyer can get caught out badly by not understanding how they work.

Optical zoom
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This is the zoom spec which matters. Optical zoom is provided by the lens (i.e. the optics) and does not lose image quality. The zoom is provided by a telephoto lens.

Optical zoom lenses actually “move” you closer to the subject of the photograph without sacrificing quality. The higher the optical zoom rating on a camera, the farther away you can be to take a photograph and still get a clear, close-up image. The concept of optical zoom essentially the same as the zoom on a film (non-digital) camera. Optical zoom is the number you want to pay close attention to--it’s the zoom that will give you the quality results you want.

Digital zoom
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Digital zoom on the other hand is not bringing you closer to the item. Rather, the camera crops the entire image, and then digitally enlarges to the size of the viewfinder the portion you want to zoom in on. This results in a loss of quality, and is no different than cropping and enlarging an image with editing software. The benefit of using image-editing software instead of the digital zoom on a camera is that you can decide how much to crop, and how much to enlarge the image to where the quality is acceptable to you. When you use digital zoom on the camera, the image quality is irreversibly lost.

Digital zoom works by magnifying a part of the captured image using digital manipulation. This is the same as how a graphics program resizes an image to a larger size. The process involves taking a certain number of pixels and creating a larger image, but because the new image is based on the same number of pixels, the image loses quality. At small zooms (up to 20x) the loss may not be too noticeable. At large zooms (up to 100x or more) the quality becomes absolutely terrible.

Some digital zooms use interpolation, which is a way of estimating the value of the new pixels rather than simply duplicating existing pixels. In theory this should reduce the loss of quality, but no amount of interpolation will prevent loss altogether.

Remember that digital zoom can be done in post-production with any half-decent editing software, so you really gain nothing by having the camera do it.

The bottom line
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The camera’s zoom capabilities can make a difference as to how much cropping you will need to do in the editing stage. You may be happy with a lower megapixel rating but higher optical zoom if you compose your photos with the zoom lens first, then print the photos as-is. On the other hand, if you like to crop and edit your photos after the fact, a higher megapixel rating and lower optical zoom capability will still allow you to “zoom” with your editing program and compose a photo that can be printed at the size you desire (keeping in mind the minimum pixel sizes for various sized prints). Your style and comfort level of photography and photo editing will help decide which is more important to you.

Compare optical zoom and ignore digital zoom. Optical zoom capabilities make all the difference in the final product. The higher the optical zoom, the farther away from the subject you can be and still get a great, clear, crisp quality shot.

Answer 3

Both optical zoom and digital zoom are means to magnify an image, but they work in different ways. Optical zoom will always yield a far superior image than digital zoom.

How does optical zoom work?
A digital camera that offers optical zoom works the same way as a zoom lens on a traditional camera. A traditional lens works by collecting light rays and projecting them onto a piece of film, or in the case of a digital camera, onto the sensor.

Unlike a fixed lens, a zoom lens has several moveable glass elements inside. By adjusting these elements, the focal length of the lens can be changed. Adjusting the focal length both changes the view distance and reduces the field of view, causing the projected image to appear larger.

In a digital camera with optical zoom, the same number of pixels are captured when the image is magnified. The only thing that changes is which rays of light are projected onto the sensor to form those pixels.

How does digital zoom work?
Unlike optical zoom, digital zoom works by scaling up the pixels in the final image after it is captured. This is very similar to cropping and resizing your picture in PhotoShop.

Answer 4

I am sure you will receive many answers to your question but all the same, I still will try to shed some light. Simply stated:

Most digital cameras comes with optical and digital zooms. Optical zoom is the only feature that you should consider if you are in for a well focussed image. Optical zoom is done by the camera's lens whereas digital zoom is done by the camera's electronics. Go for optical zoom!

Answer 5

Optical Zoom means by changing the focus length and the focus point of the lense (Which is really an optical thing) we zoom in and zoom out of the actual object and we take the picture. The pixel information stored for every pixel is based on the zooming level. But in Digital zoom we just copy the pixel information of a pixel with it's neighbourhood pixel.(Pixel is the basic fundamental thing of an image what we take.). In the digital zoom only the pixel information is changed not the actual object's dimentions.

Answer 6

Another way to look at it is that the digital zoom is zooming in on the highest optical zoom image and then cropping away part of the image. You could get basically the same result by zooming into a picture with Windows or Photoshop and then cropping away what you don't want.

Answer 7

optical zoom is done by the lenses it self, much like a magnifiying glass...when you are optical zoom the picture will still look good. With digital zoom it is the camera actually doing the calculations, much like zooming into a picture using an image viewer on the computer, so the more you zoom the more pixels or blocks you see.

Answer 8

first of all, optical zoom is better than digital zoom.

Digital zoom is a method of decreasing (narrowing) the apparent angle of view of a digital photographic or video image. Digital zoom is accomplished by cropping an image down to a centered area with the same aspect ratio as the original, and usually also interpolating the result back up to the pixel dimensions of the original. It is accomplished electronically, without any adjustment of the camera's optics, and no optical resolution is gained in the process.Because interpolation disturbs the original pixel layout of the image, as captured by the camera's image sensor, it is usually considered DETRIMENTAL to image QUALITY.

inversely optical zoom is done by the camera's optics, so the quality of the image is maintained.

Answer 9

Why is Kodak asking this question? Are you looking for something to use in your marketting? Anyhow, here's my standard answer to this question.

Optical zoom is good and digital zoom sucks. Optical zoom is "real" zoom done with the camera lens. Digital zoom is really just a way to enlarge pixels and degrade the image. Ignore it completely when you are comparing cameras.

Here are three sample pictures taken with my Canon Powershot SD900, which is a 10.0 megapixel camera. All three pictures are taken with the optical zoom maxed out at 3X or 23.1 mm, which is the equivalent of 111.6 mm after calculating for the lens crop factor. There is no image processing at all done with any of these pictures. All were taken using the self-timer to (hopefully) eliminate camera shake as the camera sat on the top of my car. (Okay, I'll use a tripod next time, but I think they are pretty sharp images.) Please click on "View All Sizes" and then view each image at the largest size available, which should be 3648 x 2736 pixels. The first picture (3xOpticalFull) is the full frame image at 3x optical zoom, or 111 mm. The second picture (4xDigitalFull) is the result of zooming out the additional 4x in digital zoom, for an equivalent of 444 mm. The third picture (3xOpticalCrop) is actually a cropped version of the original image, maintaining the full pixel dimension. In other words, I accomplished the "digital zoom" entirely in the computer and not in the camera. If you compare the full-sized images, I think it is immediately obvious that the third picture is far superior in any aspect that you care to examine. I think it is much sharper (Check the tower and the antenna up near the top of the frame.), has better color, and less digital noise and artifact (Check the plain sky and the shadows on the building.). These images are all tagged "digital zoom."

3xOpticalFull: http://www.flickr.com/photos/7189769@N04/459603923/
4xDigitalFull: http://www.flickr.com/photos/7189769@N04/459603931/
3xOpticalCrop: http://www.flickr.com/photos/7189769@N04/459603939/

In other words, please ignore any claims of superiority based on "digital zoom" when you choose your camera. It is only "in camera cropping" and it is not anywhere near as good as "in computer cropping." Any attempts at cropping a digitally-zoomed picture will be a waste of time.

Answer 10

The above answer is perfect. I would go with optical zoom. In fact on my point and shoot camera, I have disabled the digital zoom feature. You end up with pixel soup!!! Good luck

Answer 11

We can remember Old camera And Now new camera called
Digital pixel camera.
Zooming object with lens power called optical zoom.
and with pixel sceen mgnifying the object called Digital.
Hope this is crude answer. !!.