View Full Version : Two (possibly stupid) questions about digital cameras...

14th July 2004, 20:10
Question number one, I've had several people ask me this, and I'm not 100% sure of it.... so what is the difference between Optical Zoom and Digital Zoom on a camera (advantages/disadvantages of each...)

Second question... does the speed rating of a flash card REALLY matter? Especially on lower MegaPixel cameras?


14th July 2004, 20:15
moved to the right place ;)

Optical is done with the lens, and is much higher quality. digital zoom is done on the ccd element. effectivly digital zoom is a smoke and mirrors zoom.

on the memory, i'm sure some purists will shoot me, but it's really only an issue if your taking lots of pics at once.

in mine I have some medium speed flash memory, I don't have an issue, and if all your doing is family shots, scenery - no problem.

If your off the the Grand Prix and want lots of action shots, get the faster.

14th July 2004, 23:32
Sasq got it right.

Digital zoom basically takes a part of the image, and uses filtering algorithms to upsample. If you're going to do that, use a real program for it (GIMP may work, but I have no idea about its upsampling quality).

As for memory speed, the super-fast memory is likely faster than many low end cameras (ie, the camera can't write as fast as the card can be written). For some odd reason, everything is rated in "x" (such as 12x), where 1x is CD read speed - 150kB/second.

As a speed data point, the 4G Hitachi microdrive does about 7M/sec (or roughly 47x), while the fastest Lexar media is 40x or so.

Either way, if you shoot low res, and do JPEG compression, you'll only be saving ~100-200k/image, so even a "slow" 12x card can save about 8 frames/sec.

- Steve

(edit: clarity)

15th July 2004, 00:55
Originally posted by Sasq

Optical is done with the lens, and is much higher quality. digital zoom is done on the ccd element. effectivly digital zoom is a smoke and mirrors zoom. Cant agree there Dan - optical is a function of the lens sure, but digital (on most if not all digital cams) refers to the practice where part of the image seen by the CCD is cropped out of the picture, and is then presented on either the preview screen or is stored as such on the memorycard. Cropping implies loss of quality and is absolutely useless in my opinion as a "feature" on any cam - you can do exactly the same with postprocessing software (Steve) and achieve much better/flexible results there anyway.

There is no obvious advantage to having digital zoom on any camera in my opinion (not in the current simple cropping mode and fixed ratio implimentation startegies the manufacturers adopted anyway)

15th July 2004, 01:09
Yeah, speed won't matter much for lower res cams (because they don't have huge files) and cheaper or older cams (because they have slow memory interfaces anyway and couldn't make use of the extra speed). If you're shooting continuous, TIFF or RAW, a faster card may help. Just don't get one of the old Sandisks, they're terribly slow. The Ultra II are blazingly fast, but you don't need that :)

Optical zoom: The lens moves. "real" zoom, high quality.

Digital zoom: Just like what you can do in any image editing software on the PC. Takes a part of the image (say the middle 640x480) and blows it up to full image size (say 1280x960) - as you can see, you now have a larger file, and you may even think you can see some more detail, but you can't. Because only 640x480 sensor pixels were used in taking the image. That's not to say digital zoom doesn't have any right to exist, I just think it shouldn't be integrated in cameras and shouldn't be called zoom, because it isn't. It should be called magnify or resample or something like that.


15th July 2004, 01:16
but 'zoom' sells better.

LvR, last I checked the CCD itself usually has the feature built in. It has been a while since I looked at the interface for a CCD chip though.

On my camera I have it turned off from memory. It is useful for takeing a peak at something that will be in the shot, but yes, better to post process.

Hence my comment about it being a smoke and mirrors 'zoom' - its not real.

15th July 2004, 01:29
On an electronic level you are correct Dan - the CCD drivers may have that ability, but its not used that way on most if not all digital cams on the market currently - you can see the optical zoom being used to its max at which point if digital zoom is switched on and you "zoom" further, you will immediately start seeing blocky artifacts appearing allover the picture because of cropping.

15th July 2004, 02:36
Yeah, all digital "zoom" gives you is fewer and bigger pixels (of course some manipulation is applied to hide block structures etc, but in essence it's just that, and you can do it in an image editing program).

OK, I think we've repeated ourselves enough here, we should give leech a chance to respond ;)


15th July 2004, 04:15
Wow... thought I'd get one or two responses... First I want to apologize for not getting it in the right forum.. In fact, I swear when I looked, I saw Desktop Video, then General Hardware/Software... so I put it there... I had thought previously that there was a digital imaging forum, but didn't see it when I looked.. but it's here, obviously... I'll blame it on the chemicals I work with...

At least I know the explanation I was giving to people is right. On both accounts. I just wanted verification :D

As I had explained it to people who asked me, the faster flash memory was for consecutive picture taking, for instance, the Sony Cybershot cameras have a setting that will take rapid pictures, for kind of a stop frame animation or something. And I usually explained the zoom as the optical being with actual lenses, like an old fashioned zoom, and the digital is more like what you'd do with Photoshop, Gimp, Painthop, etc.


15th July 2004, 04:30
Completely right, though I want to add that almost all but the most basic digicams (and even many of them) from all manufacturers have continous shooting modes. My camera, for instance, takes up to four (I think) pics at 3 fps, or up to 40 or so at 7 (!) fps at a reduced resolution.

There are true things that are truly unique to sony cams: Nightshot/Nightframing (though you can do infrared photography, which nightshot is a fancy name for, with other cams, they just don't have built-in IR LEDs to light up the scene), and that laser focusing system (which works well, but some other AFs work equally well and fast or faster).


15th July 2004, 16:27
I don't think my camera has the quick shot feature, but then again, it's pretty old. But it does have the optical zoom and digital zoom.

IR would be pretty sweeet. How much does one of those run?


16th July 2004, 00:47
Depends - as I said, there are numerous cameras with which you can shoot IR, not just the sony ones. The only difference is that the sony ones have an IR filter (that lets IR pass and blocks out the visible spectrum) built in that is automatically activated in the lens when you switch to nightshot, for other cams you have to buy such a filter and screw it onto the filter thread (if you have one). As a cheap solution, you could just hold it in front of the lens. The only thing you have to be carefulk about is if the cam has a built in circular IR filter, like the Dimage 7i and later (the Dimage 7 doesn't) - you'll get a bright spot in the middle then. Unfortunately, you won't find stuff like that in the specs, you'll have to search through forums yourself. I don't know any cams off-hand, sorry.

some examples (http://www.pbase.com/equinoccio/ir) (Shot with a Dimage 7 + Hoya R72 filter).


17th July 2004, 04:58
Well, I looked again, and discovered why I posted in the wrong forum... there isn't a link on the main page for the Digital Imaging forum.... not my fault after all...