Sign in with
Sign up | Sign in
Your question

What is digital zoom?

Last response: in Digital Camera
Share
May 22, 2005 1:34:08 AM

Archived from groups: rec.photo.digital (More info?)

I know digital zoom is not real zoom, it just cropps the image, but
why are the image files the same size as unzoomed images, because
when I crop images on an editor, the size of the file usually becomes
dramatically smaller?

More about : digital zoom

Anonymous
May 22, 2005 1:34:10 AM

Archived from groups: rec.photo.digital (More info?)

"Eric Gill" <ericvgill@yahoo.com> wrote in message
news:Xns965DA3A9B39C5ericvgillyahoocom@208.49.80.124...
> <news> wrote in news:428f9b65_2@mk-nntp-2.news.uk.tiscali.com:
>
>> I know digital zoom is not real zoom, it just cropps the image,
>
> ...and then upsamples it. A very bad idea.
>
> http://www.bobatkins.com/photography/digital/digital_im...

I have yet to see a camera where it doesn't degrade the image. Gotta read
those specs carefully when you buy a new camera, and if possible turn off
digital zoom. I've seen a few cameras that advertise 16x Zoom, where the
optical zoom is only 3x, or something like that. And the cheaper point and
shoots are all digital zoom.
Related resources
May 22, 2005 2:43:01 AM

Archived from groups: rec.photo.digital (More info?)

If you work it carefully there can be some advantages, the main one
being that you can get a very accurate exposure in camera rather than
when you post process. I would only use it if I did not have a
conversion lens and even then would not use it to its maximum. This all
said don't discount it entirely on a good camera with an optical zoom
and no add-on lenses. I would not consider it on a point and shoot that
offers it as its only zoom. All in all it is best to work with a good
imaging program.

Sheldon wrote:
> "Eric Gill" <ericvgill@yahoo.com> wrote in message
> news:Xns965DA3A9B39C5ericvgillyahoocom@208.49.80.124...
>
>><news> wrote in news:428f9b65_2@mk-nntp-2.news.uk.tiscali.com:
>>
>>
>>>I know digital zoom is not real zoom, it just cropps the image,
>>
>>...and then upsamples it. A very bad idea.
>>
>>http://www.bobatkins.com/photography/digital/digital_im...
>
>
> I have yet to see a camera where it doesn't degrade the image. Gotta read
> those specs carefully when you buy a new camera, and if possible turn off
> digital zoom. I've seen a few cameras that advertise 16x Zoom, where the
> optical zoom is only 3x, or something like that. And the cheaper point and
> shoots are all digital zoom.
>
>
Anonymous
May 22, 2005 7:33:36 AM

Archived from groups: rec.photo.digital (More info?)

news wrote:
: I know digital zoom is not real zoom, it just cropps the image, but
: why are the image files the same size as unzoomed images, because
: when I crop images on an editor, the size of the file usually becomes
: dramatically smaller?

If you crop the image and then expand the cropped image to the original
size of the uncropped image, that would be roughly equivalent to "digital
zoom" on the camera. The crop is not the problem. It's the following
expansion of the crop to the larger size that causes inconsistancys. IMHO,
a digital zoom may be useful for locating and identifying the subject
prior to actually taking the photo. But I will always go to the optical
zoom range for the actual picture and do any cropping in post production.
I have found that, most of the time, any expanding of an image in post
production will be more clear to the eye than a digital zoom image. A
digital zoom requires a small chip to do the upsample in a very short
time. But on my computer at home the computer is much more powerful and
can take longer, running a much more complicated program that should do a
more esthetically pleasing upsample of the data.

Of course this is my personal experience and others may have different
opinions (tho I rarely see different opinions expressed). :) 

Randy

==========
Randy Berbaum
Champaign, IL
Anonymous
May 22, 2005 9:09:17 AM

Archived from groups: rec.photo.digital (More info?)

<news> wrote in message news:428f9b65_2@mk-nntp-2.news.uk.tiscali.com...
> I know digital zoom is not real zoom, it just cropps the image, but
> why are the image files the same size as unzoomed images, because
> when I crop images on an editor, the size of the file usually becomes
> dramatically smaller?
>
>
I think your cam 'upsampels' your cropped image so that all
your files in your cam have the same size. Otherwise there would
be a total mess for most ppl when postprosessing shall start.

....I do understand the industri at this point.

AP
Anonymous
May 24, 2005 6:01:39 AM

Archived from groups: rec.photo.digital (More info?)

In message <428f9b65_2@mk-nntp-2.news.uk.tiscali.com>,
<news> wrote:

>I know digital zoom is not real zoom, it just cropps the image, but
>why are the image files the same size as unzoomed images, because
>when I crop images on an editor, the size of the file usually becomes
>dramatically smaller?

That's a very good question. I've always wondered why they try to
normalize the size. It doesn't help the image quality any, to do so; in
fact, it can soften the entire image, not to mention waste card space.

Ideally, a camera with digital zoom would only be zooming in the preview
or electronic viewfinder; what happens to the image itself is just
cropping, and the more you zoom in, the smaller the file is.
--

<>>< ><<> ><<> <>>< ><<> <>>< <>>< ><<>
John P Sheehy <JPS@no.komm>
><<> <>>< <>>< ><<> <>>< ><<> ><<> <>><
Anonymous
May 24, 2005 1:24:57 PM

Archived from groups: rec.photo.digital (More info?)

>>>I know digital zoom is not real zoom, it just cropps the image, but
>>>why are the image files the same size as unzoomed images, because
>>>when I crop images on an editor, the size of the file usually becomes
>>>dramatically smaller?
>>
>>That's a very good question. I've always wondered why they try to
>>normalize the size. It doesn't help the image quality any, to do so; in
>>fact, it can soften the entire image, not to mention waste card space.

I have a nasty suspicion that the reason the camera manufacturers
extrapolate is in order to meet layman users' expectations - ie. that
digital zoom will give them the same resolution image (in terms of pixel
size) but for a smaller area of the view. Most people enthusiastic enough
to frequent forums like this will have thought about the process and
realised that you cannot get something for nothing - that a 4MP camera, for
example, won't produce a true 4MP image at 2x digital zoom. I suspect that
a large proportion of the mass market digital camera users have never given
it a moment's thought and aren't even aware of any quality issues when
comparing digital to optical zoom.

Digital zoom is also useful if you are too lazy to perform the cropping on
computer - or even if you don't have a computer and/or relevant software.
There are plenty of happy snappers out there who are willing to treat their
digital images like film - ie. throw them to a high street developer without
any further processing and live with whatever comes back.

I must admit that I frequently use my digital zoom out of pure laziness. I
rarely bother with much post processing on holiday snaps, for example.

But before dismissing digital zoom out of hand as a wombat*, it occurs to
me that there is one very minor advantage to extrapolating in the camera.
If you are asking the camera to produce jpeg, as opposed to uncompressed
images, the camera's extrapolation gets to work on the picture _before_ it
is jpeg compressed. It strikes me that this may carry a small advantage.
Of course, this is nullified if you work on raw images anyway.

Keith

*Just in case it's not in common parlance in all parts of the English
speaking world, "Waste Of Money Brains And Time".
Anonymous
May 24, 2005 1:42:01 PM

Archived from groups: rec.photo.digital (More info?)

Keith Sheppard wrote:
[]
> But before dismissing digital zoom out of hand as a wombat*, it
> occurs to me that there is one very minor advantage to extrapolating
> in the camera. If you are asking the camera to produce jpeg, as
> opposed to uncompressed images, the camera's extrapolation gets to
> work on the picture _before_ it is jpeg compressed. It strikes me
> that this may carry a small advantage. Of course, this is nullified
> if you work on raw images anyway.

I have seen exactly this effect on a Nikon 990, where the digitally-zoomed
JPEG image was just superior to the unzoomed image. I was careful to test
at exactly 2:1 digital zoom so that the camera had an easy job of
interpolating the data. You may also see improved focussing and exposure
due to the camera concentrating on the wanted part of the image and not
the whole area.

Having said all that, I would not normally recommend digital zoom, and
deplore its use as a marketing ploy.

Cheers,
David
Anonymous
May 25, 2005 3:54:45 AM

Archived from groups: rec.photo.digital (More info?)

In message <JpCke.16352$hn5.9254@newsfe2-win.ntli.net>,
"Keith Sheppard" <keith.sheppard@tesco.net> wrote:

>>>>I know digital zoom is not real zoom, it just cropps the image, but
>>>>why are the image files the same size as unzoomed images, because
>>>>when I crop images on an editor, the size of the file usually becomes
>>>>dramatically smaller?
>>>
>>>That's a very good question. I've always wondered why they try to
>>>normalize the size. It doesn't help the image quality any, to do so; in
>>>fact, it can soften the entire image, not to mention waste card space.
>
>I have a nasty suspicion that the reason the camera manufacturers
>extrapolate

This is interpolation. Extrapolation would be projecting the image
outside of its original borders, I think.

>is in order to meet layman users' expectations - ie. that
>digital zoom will give them the same resolution image (in terms of pixel
>size) but for a smaller area of the view. Most people enthusiastic enough
>to frequent forums like this will have thought about the process and
>realised that you cannot get something for nothing - that a 4MP camera, for
>example, won't produce a true 4MP image at 2x digital zoom. I suspect that
>a large proportion of the mass market digital camera users have never given
>it a moment's thought and aren't even aware of any quality issues when
>comparing digital to optical zoom.

Yes, I realize this. I tend to be a bit facetious at times to highlight
a peeve.

>Digital zoom is also useful if you are too lazy to perform the cropping on
>computer - or even if you don't have a computer and/or relevant software.
>There are plenty of happy snappers out there who are willing to treat their
>digital images like film - ie. throw them to a high street developer without
>any further processing and live with whatever comes back.

>I must admit that I frequently use my digital zoom out of pure laziness. I
>rarely bother with much post processing on holiday snaps, for example.

Digital zoom is not a bad thing, either, if, for example, you have the
output file size set to a small fraction of the camera's full resolution
for some low-res need, provided no up-sizing of original pixels is
involved.
--

<>>< ><<> ><<> <>>< ><<> <>>< <>>< ><<>
John P Sheehy <JPS@no.komm>
><<> <>>< <>>< ><<> <>>< ><<> ><<> <>><
!