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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?

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No.⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀ –  enthdegree Jun 11 '11 at 23:22
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Surprisingly, there are actually answers here that point out some advantages I wasn't aware of. –  Octopus Apr 25 '13 at 21:13
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12 Answers

up vote 42 down vote accepted

No, it does not have much use.

Digital zoom is a restricted form of cropping:

  • It is always done around the center.
  • It is constrained to certain fixed increments.
  • It is limited in quality by the firmware of the camera.

On the other hand, cropping can:

  • Be of arbitrary size.
  • Be taken from any part of the image.
  • Be processed using a variety of state-of-the-art algorithms designed to produce higher-quality results than your camera can.
  • Is reversible if you use a non-destructive editing software such as Lightroom or Bibble.
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apparently from the other answers, there are a couple of advantages for digital zoom. I give +1 for the thoroughness of the facts list, though. –  ysap May 29 '11 at 1:34
    
OK, I had not thought about the re-compression, quite minor since after cropping you can save as PNG/TIFF or other lossless format. Luckily I used the words much use ;) –  Itai May 29 '11 at 2:09
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I think that the real advantage is actually not requiring PP at all, as per Henry Jackson's answer. –  ysap May 29 '11 at 3:18
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It's sort of misleading to say that digital zoom only crops "around the center," since you can recompose as you're shooting and frame it however you want. It's true that you can't change the composition later, though. –  Henry Jackson May 29 '11 at 21:39
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All cameras that I know zoom digitally around the center. Can point your camera any way you like but you are still going to give you a central perspective. If it gave you the same thing, people wouldn't pay so much for a shift-lens. –  Itai May 29 '11 at 23:15
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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).

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I've always wondered, but never took the time to actually check: what about metering? When you use digital zoom to zoom into an area with different lighting, can you give the camera a better idea of how to expose the part of the photo you are interested in? –  rm999 May 28 '11 at 22:18
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@rm999 - great question, and IMHO, deserves a full question by itself, as a followup to this one. –  ysap May 28 '11 at 22:40
    
Note that some DSLRs will let you actually crop in-camera too. –  Craig Walker May 30 '11 at 14:37
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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.

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Since this sort of question is bound to attract folks who don't know all of our insider jargony photography TLAs yet let me just add... "just so that someone doesn't make the mistake of thinking that not using digital zoom causes intelligence loss, in the context of @mattdm's answer, IQ = Image Quality." –  Jay Lance Photography May 29 '11 at 16:08
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Since this sort of question is bound to attract folks who don't know all of our insider jargony geek TLAs yet let me just add... "in the context of @Jay's comments, TLA = Two Letter Acronym." :-) –  Jay Lance Photography May 29 '11 at 16:10
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not a lot of cameras that produce RAW output would have a digital zoom option, the customer base for both isn't at all the same :) –  jwenting May 30 '11 at 5:07
    
The camera might also decide to compress a digitally zoomed image less, since it would naturally be a smaller file to begin with. This could also lead to a higher quality image than if you cropped later. –  Evan Krall May 30 '11 at 5:25
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JPEG can be cropped losslessly, using e.g. jpegtran. –  Mechanical snail Aug 24 '12 at 2:25
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Digital zoom may also help with exposure, by cropping out relatively bright or dark zones.

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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:

jet-skiing

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But, more useful than cropping later? –  mattdm May 29 '11 at 12:22
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@mattdm yes, 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. E.g. this picture would've been hard to focus using full resolution - link –  Imre May 29 '11 at 15:35
    
Sounds good to me. :) –  mattdm May 29 '11 at 15:50
    
Great answer Imre, perhaps put edit that comment into your answer for clarity. –  fmark Jun 12 '11 at 6:54
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Second paragraph says it all; "when you're shooting less-than-maximum resolution JPEGs". I'd actually never considered that. –  Octopus Apr 25 '13 at 21:09
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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.

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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.

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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!

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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.

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The arguments seem valid, however, as for 2.a, you will save your digitally zoomed image at best quality and thus should get comparable file size. –  ysap Sep 8 '11 at 18:43
    
@ysap - nope, see 2.b! Moreover, what I meant with 2.a, is that you don't need best quality to save digitally zoomed image - and still you will get better result than using best quality and doing crop and resize in post-process. –  Tomas Sep 8 '11 at 19:29
    
Note I bolded the 2.a - by itself, I don't think the assertion is correct. It is implied in 2.b, though. –  ysap Sep 8 '11 at 23:24
    
@ysap, nope, 2.a says that when using digital zoom, you can safely set your camera to lower quality setting. Which by itself implies that the file size will be lower, disregarding what is said in 2.b. –  Tomas Sep 8 '11 at 23:43
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On the other hand, a person who really cares about IQ wont be using digital zoom, shooting jpeg, nor worrying about saving a few Kb per image. –  Michael Nielsen Nov 18 '12 at 19:24
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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).

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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] :)

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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 ...

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