I've always wondered what is the use of digital zoom, apart from viewing the subject clearly on the LCD display.
We can take a photo with the optical zoom and crop the photo to the desired region of interest.
How does a photo taken with digital zoom compare with the cropped one? What are the advantages of having a high digital zoom?
No, it does not have much use.
Digital zoom is a restricted form of cropping:
On the other hand, cropping can:
I think an important advantage is saving time. When you happen to shoot hundreds of photos in a row stuck with a lens wider than would be optimal, cropping each one of the images into a smaller size in post processing would be quite tedious - usually you can't do that in batch unless you really don't care about resulting framing. Framing on spot, on the other hand, is something you'll have to do anyway.
When you're shooting less-than-maximum resolution JPEGs, digital zoom will retain more image information than you'd get by cropping later. E.g. when shooting 6MP images with a 16MP sensor, cropping a half-height-half-width image will result in 1.5 MP of information, whereas using digital zoom on spot would store image based on information of 4MP.
In some cameras (such as my old Panasonic DMC-FZ30) digital zoom is equal to extra optical (tele) zoom when you are shooting video or photos with less than maximum sensor resolution (e.g. for web use only). Using digital zoom, the camera would use smaller area of sensor to compose the picture, but not less pixels than in resulting file.
I mostly shot water sports for web / computer display with that camera and found the extra reach with 3MP much more useful than full 8MP resolution. With the extra zoom, the person was larger in EVF for lining up with a focusing point (quite hard with extreme zoom and subject speed), the files were smaller, and I had to spend much less time at computer. For example, this picture would've been hard to focus using full resolution:
Same photo will result from using digital zoom or cropping.
Advantage of digital zoom: you don't need a computer to crop it. You can upload straight to Facebook, print it out, etc. Cropping is a very common post-processing technique and this lets you do it easily, on the fly.
Advantages of cropping after the fact: you can take more time to compose the crop (and change your mind later).
If your camera only saves in JPEG, using digital zoom instead of cropping later avoids IQ loss from compressing twice. This is usually minor, but there it is.
jpegtran.
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Commented
Aug 24, 2012 at 2:25
Digital zoom may also help with exposure, by cropping out relatively bright or dark zones.
Yes, when saving to JPEG, the digital zoom is useful! Looking at the answers, it is surprising how many people is not aware of it!
1) you will achieve better quality. Just make a test and you will see. There is a JPEG artifact, which works at few-pixel scale, and this artifact will be enlarged as you will crop and zoom the image in post-process. It is especially strong for lower quality settings. When you digital zoom in the camera, the pixels are enlarged before they are first saved to JPEG so they are not affected by the JPEG artifact.
2) you will save space on the card. If you do digital zoom instead of keeping the full frame, then
a) you don't need the largest JPEG quality setting to obtain a good quality crop later
b) the resultant JPEG got from optical zoom will be much smaller then the full frame, even if it has equal dimensions and quality setting - because the picture is more blurred, more uniform, so it can be better compressed with JPEG.
The only advantage I can come up with is if you're planning to take the memory card out of the camera, put it into a print machine in a store somewhere, and have them print the pictures. Nice for those vacation snapshots you're getting printed onto cardstock on location to send as postcards to the family, or for people who don't want to bother with postprocessing, but no more.
If you're going to do any post processing at all, having the full image and cropping and rescaling yourself in quality software will typically yield better results as well as giving you more freedom.
Digital zoom is useful for people whose aim when taking photos is not quality, digital zoom is a way of making things easy. This is why most cameras offering digital zooms are just point and shoot, cameras intended for youtube use or similar products for people who want their content right on the web straight from the camera.
However, I have observed that cameras capable of cropping in camera can offer a little bit more quality at expense of the loss of Megapixels. By Cropping I mean "post processing done in camera". Normally this is done by using "playback" mode, zooming and panning the picture you have already taken, and hitting some option to "save what you see". The camera then saves a copy of your picture with a new file name that contains only a portion of the image. The resulting image is usually smaller in pixel count but roughly the same quality as the original. The advantage here is, you get both, the "zoomed" image and the original, right out of the camera. This method usually limits the "steps" of framing that are allowed, but then again, this functionality is aimed for people who is not primarily focused in picture quality. For everyone else, there is post production!
To add to @Imre’s answer a bit, there are situations when using the digital does seem to help the camera to identify the right area to focus on. I’ve been to a few performances (indoor, stage lighting) where my camera (Canon G9) has found it difficult to focus on the people on the stage. Sometimes it would get it right, but others it would hunt / pick the wrong focus distance. By using the digital zoom, to reduce the area that the camera cared about it seems to help the camera pick the right focus far more consistently.
The other area that the digital zoom is useful is when using the camera to shoot video. Some camera’s (including the G9) don’t let you use optical zoom whilst taking videos, however they do let you use the digital zoom. The advantages of the digital zoom in this situation are that you get to silently adjust the zoom / crop factor for the video (as video resolution is lower than the camera’s native there’s certainly scope for doing this with reasonable results) and digitally zooming in / out doesn’t impact your focus (so in difficult situations you can zoom in to help the camera achieve focus lock, then zoom back out if you want without having to refocus).
Wow - most of these answers surprise me very much! I've done a lot of research on this and have found out that good camera makers are currently able to implement very effective Image Stabilizers in digital zooms. Therefore the difference is HUGE!!! If you really need a closer shot and don't have additional optical zoom (with IS) - just use the digital zoom! The result will be much better than cropping it later with any desktop software on a personal computer.
If you don't believe me - just try it out - you will be very surprised ... provided that you're using an adequate camera ...
I have no idea why the manufacturers still offer the digital zoom.The result is mostly bad and I have no influence on the way how the photo is processed. When I do the same in GIMP, I have much more freedom to set the parameters of used method etc. I also have the source, untouched image, which i do not have when using camera built-in digital zoom.
This is a personal opinion but to me, digital zooms are abhorrent. Once you reach the limit of the optical zoom, what can the camera do to zoom any more? It basically has to pixel-double, with some special sauce thrown in, in the in-camera software, to smooth edges and allow a varying zoom range beyond the maximum of the optical.
The result is (in my experience) poor quality photos, exhibiting alaising along high-contrast edges, lack of what should be fine detail because it never had that detail in the first place, and noise is amplified.
Really, using digital zoom does not add up to a good photo.
[steps off soapbox] :)
