Go Back   Steve's Digicams Forums > Digicam Help > General Discussion

Reply
 
Thread Tools Search this Thread
Old Jul 6, 2004, 1:32 PM   #1
Junior Member
 
Join Date: Jul 2004
Posts: 5
Default

I am about to buy my first advanced digicam after struggling with a lowly no-zoom digital HP for few years. I do need a zoom longer than the regular 3x optical zoom and I expect that I will rarely, if ever, need a resolution higher than 3 Mpixels.

I have narrowed my choices down to two very different cameras at this point. Olympus C-765 with 4 Mpix and 10x zoom would certainly be a perfect choice. The only inconvenience of this camera is that it is a bit bulky; I'd rather have something that fits in my pocket.

The other camera that I am interested in would easily fit any pocket. It's Olympus C-60 (or even C-50) but it has only a 3x zoom. However, the resolution is 6 Mpix and it has a 4x digital zoom.

I would be interested in any opinions about usefullness of the digital zoom in this scenario.Is a 6Mpix camera used for 3Mpix pictures with a digital zoom plusan optical 3x zoom really comparable to a camera that has a 10x optical zoom from the beginningwhen it comes to the quality of pictures?
z220 is offline   Reply With Quote
Sponsored Links
Old Jul 6, 2004, 2:17 PM   #2
Administrator
 
Join Date: Jun 2003
Location: Savannah, GA (USA)
Posts: 22,378
Default

Ignore Digital Zoom in a camera. All this is doing is cropping the center of the image (removing the center portion, and discarding the surrounding area).

So, you end up with a very low resolution image to start with (since you are throwing part of the image away. Then, the low resolution image is enlarged (causing it to degrade severely).

You can accomplish the same thing using software later, cropping the image as desired. Also, you'll most likely be able to do a better job enlarging any cropped area with software, too.
JimC is offline   Reply With Quote
Old Jul 6, 2004, 2:31 PM   #3
Senior Member
 
Join Date: May 2003
Posts: 180
Default

Jim C is right of course, just get a 5-6MP camera and crop afterwards. I do this with my 5MP 3x zoom Sony. In fact it is one of the greatest assets for me of moving up from 3MP to 5MP.

However it is worth noting the Sony digital zoom called Smartzoomoperates in a way that doesn't lose quality. It works by using the extra "headroom" when the camera is set to a resolution lower than the maximum.

On a 5MP camera this gives a total zoom of 3.8x at 3MP and 6.1x at 1.2MP.

I would still tend to crop on the PC afterwards though rather than using it.

Never forget the digital cameras are good but not magic. Unless you are in brilliant light a long zoom at maximum may well have problems gathering enough light to keep a shake-free shutter speed.

David
Cybershot455 is offline   Reply With Quote
Old Jul 6, 2004, 3:24 PM   #4
Senior Member
 
Join Date: Jun 2002
Posts: 394
Default

My opinion is that a crop is a crop in or out of the camera. The only risk is with the digital zoom on you could end up using it when you really did not want to. Myself I like to use a digital zoom in combination with spot focus for some small birds and the like. I would be the first to agree that cropping in an editor could be superior with some shots as you can compose and/or frame the shot better thanin camera.
normc is offline   Reply With Quote
Old Jul 6, 2004, 3:26 PM   #5
Senior Member
 
Join Date: Jan 2004
Posts: 397
Default

I'm not sure just what digital zoom does. Let me state my understanding and someone correct me if I'm wrong.

I have a 3 MP (2048 x 1536 = 3,145,728 pixels) camera.

It has a 4x digital zoom (in addition to its 10x optical)

If I use the 4x digital zoom the camera will take 1/4 of the height and 1/4 of the width yielding an image with a resolutionof 2048/4 x 1536/4 = 512 x 384 =196,608 pixels.

The camera will then take that low resolution image and interpolate it back up to 2048 x 1536 for a 3 MP image. It that's right, then the camera is doing a lot of guessing on the 2,949,120 pixels of info it does not have.

IS THIS RIGHT?
Puck M is offline   Reply With Quote
Old Jul 6, 2004, 4:01 PM   #6
Senior Member
 
TheGhost's Avatar
 
Join Date: Nov 2003
Posts: 103
Default

Digital zoom is not actually a zoom, but rather its software in the camera that enlarges the current image it sees. When you play with the optical zoom, you'll feel rotary action in the camera because the lens is being adjusted. With digital zoom, it's quiet and motionless because the camera is working internally to enlarge the picture. So downsizing a 6MP camera to 3MP and using digital zoom won't gain you extra quality (it's actually the exact same!). Typically if you want to use digital zoom, you should downsample your image by 1/X, where X = digital zoom strength. This way the zoom doesn't stretch the image, but then why make life so difficult? You'd get the exact same quality by just using optical zoom and cropping out the image later. Digital zoom works best for spotting and focusing.

I would personally go for the 10x optical. 10x is very strong, coupled with 3MP you would get excellent images. If you buy a 2.4x teleconverter for it, you would get an insane 24x optical zoom. If portability in the pocket is that big of a deal, then I suppose you could just buy an expensive teleconverter that can give you up to 10x worth of optical zoom and go with the other model. However lugging one of those buggers around would be more burdensome than the camera that had it built in.
TheGhost is offline   Reply With Quote
Old Jul 6, 2004, 5:14 PM   #7
Junior Member
 
Join Date: Jul 2004
Posts: 5
Default

Thanks for all the good opinions! Obviously cropping afterwards is an option, but then, if I really want 3Mpix photos but take them in 6Mpix and crop only afterwards, it also eats twice as much memory in the camera. If we thinkdigital zoom strictly as a built-in tool for cropping,does it make any differencequalitywise in the finalphoto, whether it was cropped in the camera using digital zoom or by software later?
z220 is offline   Reply With Quote
Old Jul 6, 2004, 5:48 PM   #8
Administrator
 
Join Date: Jun 2003
Location: Savannah, GA (USA)
Posts: 22,378
Default

z220 wrote:
Quote:
Thanks for all the good opinions! Obviously cropping afterwards is an option, but then, if I really want 3Mpix photos but take them in 6Mpix and crop only afterwards, it also eats twice as much memory in the camera. If we thinkdigital zoom strictly as a built-in tool for cropping,does it make any differencequalitywise in the finalphoto, whether it was cropped in the camera using digital zoom or by software later?
Yes.. It can make a big difference.

There are many algorithms for interpolating an image. Some are much better than others. You can't expect a Digital Camera to perform as good a job in a split second, as you can do on your much more powerful PC later, taking a little longer, and using more sophisticated interpolation algorithms for resizing.

Also, because resolution is composed of width x height,it take 4 times the resolution, to double the image size. Likewise, if you use digital zoom (or crop a photo) to look like you used twice as much optical zoom, you end up with a photo that is only 1/4 the resolution before interpolation. So, significant degradation occurs when interpolating the image back up to a larger size for printing.

There is no substitute for optical zoom, if you have a genuine need to bring your subject in closer.

See this table, baseda formula described by Rodger Carter and Rick Matthews, known as Telephoto Figure of Merit:

http://www.geocities.com/digital_ray...oomzoomv5.html


JimC is offline   Reply With Quote
Old Jul 6, 2004, 6:49 PM   #9
Senior Member
 
Join Date: Oct 2003
Location: Indian Rocks Beach, FL
Posts: 4,036
Default


The C60 is about the fastest consumer camera currently on the marked according to Dave's table:
http://www.imaging-resource.com/PRODS/C60/C60A7.HTM And it is impressive that it buffers TIFF files – not many cameras can do that. I'm disappointed they didn't add long shutter noise reduction and better movies. It also doesn't have manual focus although it has all the manual exposure modes.

I've had a C50 for a couple of years now and it has served me well. But it is a little bulky for your pocket. Konica Minolta didn't seem to improve the electronics on the G600, so it is slow compared to the C60. But it fits in your pocket better and is reasonably priced. You also don't have to buy a dead-end and overpriced xD card for it. The G500/600 uses the mainstream SD memory.

The Pentax 555 is the same size as the C60 and has a 5X optical zoom. Nice camera except the shutter lag is awful. You would have to learn to pre-focus for most of your shots. The Pentax S4/4i is a nice little pocket camera if you can live with 4Mp.

I ran some C50 comparisons for you in the fading light. First shot is 3X zoom. Second is full digital zoom and the third is a crop to the same size from the first shot. I don't see a lot to choose between the digital zoom and cropping, and any difference is probably because I was shooting about 450mm equivalent focal length at 1/200 second without stabilization. The 12X shot comes to about 300k pixels.

3X optical zoom



4X digital zoom:



3X optical shot cropped:


slipe is offline   Reply With Quote
Old Jul 6, 2004, 7:13 PM   #10
Senior Member
 
Join Date: Oct 2003
Location: Indian Rocks Beach, FL
Posts: 4,036
Default


For comparison with a real 12X optical zoom I just retook the picture with 12X optical zoom on my FZ10. I blew up the engine on the back of the boat from the FZ10 shot, the original Olympus and digital zoom Olympus shots. You can see that neither digital zoom nor cropping compares to having a real optical zoom:

FZ10:



Full C50 shot:



C50 digital zoom:


slipe is offline   Reply With Quote
 
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off



All times are GMT -5. The time now is 10:12 PM.