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Old Feb 14, 2007, 2:54 PM   #1
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i was arguing this ideea with someone...

he said that it is the same digital zoom as if you crop the image and use some filters later,so you don't realy need to EVER use it..you can always do it later on the pc...

i said that if you shoot RAW that is probably the case,because you have all the information,and the white balance is not done yet, but even in raw it is a good ideea to use digital zoom,because the camera will meter only the zoomed image,and you could get the corect exposure for that small portion of the picture...
if you don't use RAW(whitch some cameras don't even have, i am talking about P&S) you would gat a much better picture if you use digital zoom because there is more information available (it doesn't get lost in the compresion) and the camera maks the corect exposure for that portion of the image...

whitch is right??


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Old Feb 14, 2007, 5:04 PM   #2
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I would say your logic is *probably* right, but it isn't inherently right.

Something I'm unclear on. Since I've only ever had DSLRs I don't know this. When you use "digital zoom" does it actually crop the middle and enlarge it to match the sensor's resolution? If so, then the algorithms used to do the enlargement/interpolation will certianly be better on a computer. The camera is limited by battery power and CPU power and I'm sure that PS and other editors use better methods do interpolate the image.

Your logic about metering only the "zoomed" region is probably the best one I've ever heard for using digital zoom. In fact, its the only one that I've ever considered agreeing with. Personally, for the reason listed in the previous paragraph, I don't think I'd do it because I can correct for exposure errors - I already have to do that any ways - but I can't correct for bad interpolation.

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Old Feb 14, 2007, 6:54 PM   #3
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If you think you might want to crop the middle you can use spot or center weighted metering. I wouldn't use digital zoom just to get center metering unless the camera didn't have it.

I have read comments to the effect that digital zoom interpolates an uncompressed image and therefore gives a little better upsampled shot. I ran some comparative tests a year or so ago and put the results up on the site. I couldn't tell the difference between a crop and digital zoom.

Most cameras resample the digitally zoomed image back to the set image size. That eliminates about the only good reason I could see for using it. There are a few cameras that don't resample the image back to full size, but I think they are in the minority.

Digital zoom can be a trap if you forget to set it back or unless you are constantly aware of when it moves into the digital range. I prefer never turning it on and depending on cropping if I need it.

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Old Feb 14, 2007, 9:02 PM   #4
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csl1131 wrote:
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... it is a good ideea to use digital zoom,because the camera will meter only the zoomed image,and you could get the corect exposure for that small portion of the picture ...
If it were that easy to meter for the proper exposure, every image taken without digital zoom would be correct so long as it wasn't cropped. In extreme situations (a lump of coal on a snow bank), the metering might be better with digital zoom, but it just as likely could be worse. Do you want the image exposed for the coal or for the snow?

Automagical metering works more often than not. If you are going to get into arguing the fine points based on digital zoom, you really should be spending your time figuring out when/why the automagical metering doesn't work and figuring out what to do about it.

It is just plain silly to use digital zoom, and as Slipe points out, it can be dangerous as well.
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Old Feb 16, 2007, 5:59 PM   #5
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My Panasonic FZ30 has an "Extended Zoom" function which crops the image in the camera to achieve a higher zoom level (up to 19x, probably around 675mm equivalent). I kind of like it because it's a lot easier to compose, correctly expose and quickly preview the sharpness of the image than it is to shoot at full resolution and crop later. The files are also smaller, which is just fine if you plan on resizing your images down later anyway.

The downside is when you forgot that you have it set to 3mp instead of 8mp and you take some photos that you really wish were at the higher resolution. Also, the photos taken at the far end of that zoom range have a higher tendency for noise since you are seeing the pixels more up close.
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Old Feb 16, 2007, 7:30 PM   #6
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I'll just though my 2 cents worth in. I should mostly with a dslr, but I also have a Canon SD400 that I carry with me all the time and an Olympus C2020-Z that I use for infrared. The very first thing I did when I got these cameras is turn off the digital zoom. I can't speak for some of the newer digacams, but for what I've seen the image quality really suffers when you use digital zoom.
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Old Feb 16, 2007, 8:18 PM   #7
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Whatever you can do in both the camera and in post-processing (digital zoom vs. cropping, etc.,) it will always be done better and with greater precision and flexibility in post-processing. And post-processing provides a significant capability that no camera has. That capability is ...
UNDO!!!
Use your camera to record a color image, move it to your computer, open it in Photoshop, and convert it to B&W. If you don't like it, you can undo.

Use your camera to record a B&W image, move it to your computer, open it in Photoshop. If you don't like it, how do you tell Photoshop to restore the color? How do you tell the camera?

You will always be better off when taking advantage of the best of each of the parts of digital photography: the camera, and the computer. Use the the camera for its lens and its image sensor (and its portability), and use the computer for everything else. Including, btw, exposure. RAW, JPEGor whatever.

My $1/50.
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Old Feb 17, 2007, 10:17 AM   #8
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Whatever you can do in both the camera and in post-processing (digital zoom vs. cropping, etc.,) it will always be done better and with greater flexibility in post-processing than in the camera.
"Always" and "never" are dangerous words to use in a discussion between reasonable people with varying opinions. But since you seem to like absolutes, Corpsy has provided a couple.

If you have a camera with a digital zoom that doesn't resample the picture back to full size, you are just using space on the card for the actual pixels recorded by the sensor at the set quality. If that allows you to fit more photos on your card, the photos you take after the card would otherwise have been filled are "always' better than the photos you weren't able to take.

If you are able to visualize through the viewfinder better with the subject zoomed to the final frame, then any photo improved by changing perspective will "always" be better than anything you can do in an image editor after cropping a poorly composed photo.

I don't use digital zoom, but can see reasons for using it. I might find I compose some long zoom shots better if I digitally zoomed, but digging in the menu is just too much hassle and I would eventually forget to turn it off and grab a fast shot with it.

I did have a camera that didn't resample a digitally zoomed image and didn't use digital zoom with that camera either. But that might be a factor as well for someone with limited camera memory.

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Old Feb 17, 2007, 11:19 AM   #9
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slipe wrote:
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If you have a camera with a digital zoom that doesn't resample the picture back to full size, you are just using space on the card for the actual pixels recorded by the sensor at the set quality. If that allows you to fit more photos on your card, the photos you take after the card would otherwise have been filled are "always' better than the photos you weren't able to take.
That's not a limitation of the camera; it's a limitation of the card the user chose to put in it. If someone wants to conserve space on their memory card, there are lots of ways to do it. If, from among the multiple options available,the user chooses to engage the digital zoom to conserve space (and the camera they are using actually does use less spacefor images that are digitally zoomed), that's their choice, not a limitation of the camera.

slipe wrote:
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If you are able to visualize through the viewfinder better with the subject zoomed to the final frame, then any photo improved by changing perspective will "always" be better than anything you can do in an image editor after cropping a poorly composed photo.
Ok, this is a stretch, but I'll give it a go.

If what the user sees through the viewfinder after engaging the digital zoom makes them take a shot that they would not have taken had they not engaged the digital zoom, then you are correct. If we were talking about the cost of purchasing and developing film, if we were talking about taking the time to unload one roll of 24 exposure film and load another, if we were talking about having to wait for the drug store to develop the film, then I would say that your's is a valid argument for the use of digital zoom. But since film cameras don't have digital zoom, then I can't. If someone is interested enough to engage the digital zoom, then I suggest that they are probably also interested enough to take the shot, digital zoom or not.

But I may be wrong.

And cropping a poorly composed photograph in an image editor is the reasonbudding photographers want image editors. Would you not agree that composing an image in the camera is a more tedious and less precise process than composing an image in an image editor?
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Old Feb 17, 2007, 12:07 PM   #10
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And cropping a poorly composed photograph in an image editor is the reason budding photographers want image editors. Would you not agree that composing an image in the camera is a more tedious and less precise process than composing an image in an image editor?
I would agree only if you consider cropping the limit of composition. The shot might look a lot better taken from a different place, or higher or lower if you have an articulated LCD. One might be able to make those judgments better with a full view of the final image.

All that might not be true for a DSLR with a good viewfinder in the hands of someone with a good eye for composition and what the final crop will include. But everyone doesn't have the ability to project that well or have that good a viewfinder. For those framing with a LCD or low quality EVF they might take a completely different picture if they can digitally zoom to the target framing.

As far as memory space is concerned, people are sometimes on budgets when they buy cameras. And people sometimes find themselves on vacation with no place to store their photos and want to use their camera memory judiciously. The discussion doesn't apply to most cameras that resample the digitally zoomed photo back to full size. But for people with an intelligently designed camera it can be a consideration.

I never use digital zoom. I might do better with my little pocket camera in some situations if I did. I often end up with crops that don't look as good as I had anticipated that might well have been better had I seen the actual shot in the LCD. It isn't worth digging into the menu to both set and deactivate digital zoom. And it isn't worth taking the chance of not setting it back in a dynamic situation and not noticing I'm in a digital range. But I can see points in favor of it.

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