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View Full Version : Choosing a camera - zoom question


Debbru
09-29-2007, 12:35 PM
I am trying to choose between 2 Canons - the G9 and the S5. I love the long 12x zoom of the S5 (compared to the 6x on the G9), but the larger sensor and the 12mp on the G9 makes for some incredible photo quality.

I know that digital zoom is mostly frowned on, since it "degrades" the resolution and the same can be done later with cropping. But I was wondering -- since the G9 is a 12mp camera - what would the resolution be if you take a picture at full jpeg resolution, full 6x zoom & 2x digital zoom? Would this be a 6mp picture? or less? much less? Would the result be the equivalent of 12x zoom?

I hope this question makes sense :confused3

Debbie

MarkBarbieri
09-29-2007, 01:32 PM
I think it would be a 3mp image. If it is a 12mp camera point & shoot, it is probably 4,000 pixels across by 3,000 pixels high. If you digitally zoom in to twice the maginification, you should divide each dimension by 2. That leaves you with 2,000 by 1,500, which works out to 3mp.

Debbru
09-29-2007, 02:19 PM
Thanks! Would the 3mp picture then be the equivalent of a 12x zoom?

Debbie

MarkBarbieri
09-29-2007, 03:44 PM
The short answer is yes. I'll give a long answer to make it a little more clear (for some and more confusing for others).

Let's step back a bit. When a camera is said to have a 12x zoom, that doesn't tell you how much it will magnify things. Instead, what it is telling you is that it's most zoomed in is 12 times more zoomed in that it's most zoomed out setting. It's possible to have a 12x zoom that starts really wide and doesn't zoom in all that much. It's possible to have a 6x that doesn't get very wide, but zooms in pretty far.

What has become the standard way of comparing zoom ranges is to express them in terms of lens on 35mm film cameras. That helps photographers easily assess how wide the lens can get and how close up the lens can get. For the G9, that range is 35mm to 210mm. For the S5, that range is 36mm to 432mm. The problem with those numbers is that they are almost useless to people not used to a 35mm film camera.

Fortunately, there are calculators that will translate those numbers into something that you can understand. The one I use is at http://www.tawbaware.com/maxlyons/calc.htm.

Using that calculator, you can see that at it's widest setting (35mm), the G9 takes a picture of a subject that is about 10' 3.4" wide when that subject is 10 feet away. When you are 100 feet away from the subject and zoomed all the way in (210mm), the picture will cover an area that is 17' 1.7" wide.

For the S5, the widest setting (36mm) at 10 feet gets us a subject that is 10' wide. Taking a picture of a subject 100 feet away and zoomed in all the way (432mm) results in a picture that covers an area that is 8' 4" wide.

If you took that 17' 1.7" picture and cut out the part that is 8' 4" wide, you would have to digitally zoom 2.06x. That cuts it from 4,000 x 3,000 (12 megapixels) to 1,942 x 1,456 (2.83 megapixels). Those 2.83 megapixels you cropped from the G9 would show exactly what the S5 shows with it's 8 megapixels but would do so with fewer pixels.

In the case of these cameras, because their widest settings are about the same, the 12x zoom on the S5 gets in almost exactly twice as close as the 6x zoom on the G9. That's not always the case with other cameras.

Debbru
09-29-2007, 05:51 PM
Thanks so much for the detailed explanation (I think I understood most of it).

I checked out the photo/trip report links in your signature - absolutely amazing pics!

In your opinion, is the photo quality of the S5 close to the G9? I have the S2 now and although I really like the camera, the pics can't compare to the sample pics I've seen so far from the G9.

Thanks again,
Debbie

Caitsmama
09-29-2007, 07:18 PM
So, in basic english, ;) LOL Is it somewhat better to have a higher optical zoom number and lower mp, vs, having a higher mp with a lower optical zoom?

seashoreCM
09-29-2007, 10:02 PM
When you need to use (optical) zoom, more of it is better than more megapixels at first glance.

More specifically, having twice the megapixels is about the same as having 40% more optical zoom, all other things such as lens quality being equal. For example 8-1/2x instead of 6x or 12x instead of 8-1/2x or 14x instead of 10x.

Having 4 times the megapixels is about the same as having twice as much optical zoom.

As was mentioned above, when you compare the zoom of two different cameras, 2x on one camera can be equated with 2x on the other camera only when both have the same widest angle. Otherwise you have to do the math, again mentioned above.

Digital zoom does not necessarily degrade the picture, but it accomplishes nothing compared with blowing up the picture after downloading to your computer, and then cropping to the desired size.

Digital camera hints: http"//members.aol.com/ajaynejr/digicam.htm

MarkBarbieri
09-30-2007, 09:16 AM
I checked out the photo/trip report links in your signature - absolutely amazing pics!

Thank you. That's very nice of you to say that.

In your opinion, is the photo quality of the S5 close to the G9? I have the S2 now and although I really like the camera, the pics can't compare to the sample pics I've seen so far from the G9.
I really don't know. I don't have any experience with either camera.

It can be hard to compare via sample pics. A shot taken in perfect conditions with perfect technique with a cheap camera can look much better than a shot take with a great camera with poor technique. Reviews that show side-by-side shots are usually the best for direct comparisons, but even they can leave out shooting situations that might be important to you, like low light shooting, image stabilization capability, ability to handle contrasty scenes, or the ability to accurately capture saturated colors, just to name a few examples.

So, in basic english, LOL Is it somewhat better to have a higher optical zoom number and lower mp, vs, having a higher mp with a lower optical zoom?
Basic English isn't really my specialty. I'd just say that it depends. Longer zoom is usually better than shorter zoom (although not when the longer zoom uses a much inferior lens). More megapixels is often better than fewer megapixels, but not when it means unnacceptable increases in noise.

I wish I could give some simple rules, but there are just too many variables that aren't covered even by detailed specs. More megapixels often means smaller pixels, which is bad. But sometimes the space between pixels has been shrunk and those extra pixels might be the same size. Or maybe they shrunk the pixels and increased their number but improved the circuitry so that each pixel still performs about the same.