Steve's Digicams Forums

Steve's Digicams Forums (
-   General Discussion (
-   -   [Recovered Thread: 105907] (

anthony2816 Oct 9, 2006 6:12 PM

I currently have a Canon Powershot G2. Works well except for when I want to shoot moving things in relatively low light. A perfect example is when I go to a live play in a theatre. When I'm sitting in a darkened theatre and attempt to take a picture of the actors doing the play (and I can't use a flash, obviously), I invariably get a choice of a way-too-dark picture, or a lot of motion blurring.

I don't want to spend a fortune on an expensive dSLR rig like the Canon Rebel XTi, as I'm not really into photography as a hobby.

Would something like the Kodak Z650, Fuji S5200, or the Panasonic FZ20K (all of which are under $300) fulfill my need?

JimC Oct 9, 2006 6:25 PM

Bigger does not mean brighter.

You have to look at the largest available apertures at the focal lengths you plan on using a lens at to see how lenses compare.

Your G2 has a largest available aperture of f/2 at it's widest zoom setting, dropping off to a largest available aperture (smallest f/stop number) of f/2.5 at it's longest zoom setting (equivalent to 102mm on a 35mm camera).

It's much a much brighter lens compared to the lenses on the cameras you're considering. The f/2 you have available on the wide end of your lens is twice as bright as f/2.8 (which is the largest available aperture on most camera models), allowing shutter speeds twice as fast for the same ISO speed and lighting.

So, you'd need to shoot at ISO 800 with another camera model at f/2.8, just to match the shutter speeds you could get at ISO 400 with your Canon G2 at f/2

Now, some new camera models have higher available ISO speeds compared to your Canon G2 (which is limited to ISO 400). Each time you double the ISO speed, you can use shutter speeds twice as fast for the same lighting and aperture. But, quality varies between cameras as you set ISO speeds higher (increased noise and/or loss of detail from noise reduction).

Just keep in mind that you'd need to shoot at ISO I600 to see any significant improvement over your G2 with a model that has f/2.8 available at the focal lengths you'd use. Shooting with most cameras at ISO 800 isn't really going to give you shutter speeds faster than what you'd already have at ISO 400 (since your lens is twice as bright as the lenses on most cameras).

Are you already setting your camera to ISO 400 to get shutter speeds as fast as possible? The Auto ISO may not be going that high.

anthony2816 Oct 9, 2006 6:45 PM

Thanks for the quick and detailed reply, Jim.

I'm more of a point-and-shoot kind of person, and have never really played around with the iso setting on the G2. I just hunted around a bit and found the setting in the menu, and it was at 50, which I take it is Not Good.

I'll try cranking it up to 400 so I can learn what difference that makes.

Um, forgive is this is a question requiring too long an answer, but why not just leave the camera at the highest iso setting all the time? Does that make it too sensitive for bright daylight pictures?

JimC Oct 9, 2006 7:04 PM

ISO 50 is great if you want the most detail and least amount of noise (similar to film grain). But, that means your shutter speeds will be much slower, too.

The reason you don't want to leave it set to the highest available ISO speed is because of noise. This gives a grainy appearance to images (multicolored dots due to trying to amplify a weaker signal from the sensor).

It's a bit complex to explain. But, an image sensor is made up of millions of tiny photosites that generate a signal when light hits them. This signal accumulates while the shutter is open, then read out when the shutter closes, and if there was not enough light, it can be a weaker signal requiring more amplification.

Each time you double the ISO speed, in low light conditions where it will be selecting the largest available aperture opening for the lens (smallest f/stop number) anyway, the camera can use shutter speeds twice as fast for a properly exposed image.

That also means that there is less time for a charge to accumulate for each photosite in the sensor. So, the signal needs more amplifcation, with some photosites not registering a high enough value over dark current noise being picked up. That's what gives the grainy appearance we call noise as you increase ISO speeds.

So, it's a tradeoff. Chances are, if you set the camera to Auto ISO, it's going to vary it automatically between 50 and 200, depending on the lighting (in low light indoors, it would probably use ISO 200).

If shutter speeds are not as fast as desired using Auto ISO, you can set it to ISO 400 (at the expense of more noise in the image), for even faster shutter speeds (twice as fast as ISO 200 for the same lighting and aperture).

There are some tools you can use to reduce the appearance of noise if higher ISO speeds are needed.

One is Neat Image. They have a free demo version that doesn't expire for home use, too.

Another good one is Noiseware . They have a free "Community Edition" that doesn't expire (it's at the bottom of the list you'll see on their downloads page).

At ISO 200, you'd get shutter speeds 4 times as fast as you were getting at ISO 50 in the same lighting indoors. If you set it to ISO 400, you'd get shutter speeds 8 times as fast as you were gettting in the same lighting indoors.

Take some photos both ways and see how much noise you're willing to live with, trying the free versions of the tools I mentioned above is noise is objectionable at the viewing and print sizes you use (and it's not as obvious at smaller sizes).

It's all a tradeoff. But, your camera has one of the brightest lenses ever produced in a digital camera (you'd need to set ISO speeds twice as high with most other models to get the same shutter speeds you could get at a given ISO speed with your brighter lens).

So, I'd be inclined to see if you can get it working the way you want via camera settings before exploring other options (especially if you were using ISO 50).

If not, then explore some models with ISO 1600 or higher available ISO speeds (keeping lens brightness in mind, as some are nowhere near as bright as the lens on your G2).

anthony2816 Oct 9, 2006 7:06 PM

Okay, with the camera set on "P"rogram mode, I took a couple of pictures in low light.

With an iso of 50, the camera selected an aperture of f2.0 and a speed of 0"4.
With an iso of 400, the camera selected an aperture of f2.0 and a speed of 1/20.

The latter picture was sharper than the former, but more grainy (which I guess answers my question about always using the highest iso setting). Both settings caused the camera to give its "hold me steady for this shot" warning.

So without spending around a thousand dollars, this is about as good as it gets? The other three cameras I listed wouldn't do any better than my G2?

Sintares Oct 9, 2006 7:11 PM

Generally you want the camera to be at the lowest ISO setting unless you need a higher setting to get a faster shutter speed.

Higher ISO = more sensitive to light = faster shutter speeds = good

This comes at a draw back of more noise in the image, so image gets grainy , sharpness and detail can be obscured and colors may be faded.

Lower ISO = less sensitive to light = slower shutter speeds (may need tripod etc) but image quality is better.

JimC Oct 9, 2006 7:14 PM

Try it in the light you normally shoot in and see what you get. The human eye is not a very good judge of light levels.

Noise is worse in underexposed areas of an image (because those pixels are generating the weakest signal).

You might be able to do a bit better with some of the other models. You'd need to shoot at ISO 1600 with most other cameras to double the shutter speeds you'd get at ISO 400 with your G2 (because your lens is twice as bright as most).

Some of the newer models have relatively aggresive noise reduction systems built into them. So, visible noise may not be any worse at ISO 1600 compared to ISO 400 from your camera. But, you'd have a bit of detail smoothing from noise reduction in the cameras (they're doing it via in camera processing lately, mostly to allow higher ISO speeds).

If you use the software I mentioned in my last post, you can reduce the appearance of noise in your images, too.

If you find that shutter speeds are not acceptable in the lighting you are going to use it in, then you'd want to look at models with ISO 1600 and f/2.8 available to get faster shutter speeds than you're able to get with your G2 at ISO 400 and F/2.

But, I'd see what you get in the lighting you'd normally shoot in with your camera first.

anthony2816 Oct 9, 2006 7:22 PM

Thanks again for the replies. I'll try that noise-reduction software. Hopefully this discussion will save me some money.

At least I've learned that I'd made an incorrect assumption. I assumed that the non-SLR digital cameras with bigger lenses would collect more light than the relatively smaller-diameter lens on my Canon G2, meaning they'd automatically work better in low light situations.

JimC Oct 9, 2006 7:34 PM

Focal length is a big factor. Because those lenses are designed to go much to longer focal lengths (more optical zoom), they're not as bright as your lens. Actually, very few zoom lenses are as bright as the lens on your G2, regardless of their focal range.

Aperture (as expressed in f/stop) is a ratio between the focal length of the lens and the diameter of the aperture iris opening. So, in a longer focal length lens (more zoom), you need a larger iris diameter to let in the same amount of light.

Now, some of the Ultra Zoom lenses are pretty good with lens brightness (able to maintain f/2.8 throughout most of their zoom range). In some of the smaller models, you tend to lose a lot more brightness at the long end of their zoom range.

The lens design on your G2 is pretty good. It's got f/2 available on it's wide end (exactly twice as bright as f/2.8 ). It does drop off to f/2.5 at it's maximum focal length (zoomed in all the way for the most magnification).

But, that's still brighter than most lenses would be at an equivalent focal length + most Canon models are around 1/3 stop more sensitive than their rated ISO speed anyway, making up for some of the drop from f/2 to f/2.5. You'd be within about 1/3 stop (not much difference) in brightness shooting at ISO 400, versus a different model shooting at ISO 800 using an f/2.8 lens at the same shutter speeds.

So, unless you go with a model that has ISO 1600 and f/2.8 available (which would give you shutter speeds about twice as fast as you'd get with your G2 at ISO 400), I really don't think you'd gain anything over your existing camera.

Now, some of the newer models do have that available. But, I'd see what you get with your G2 at higher ISO speeds (up to ISO 400) in the lighting you plan on using it in before going that route, especially since you were trying to use it at ISO 50.

anthony2816 Oct 9, 2006 7:44 PM

Jim, I'm do you know that the G2 has a "brighter" lens than, say, the Kodak Z650? Is there some way to calculate this from the sales brochure specs?

All times are GMT -5. The time now is 11:52 AM.