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Old Mar 23, 2005, 5:28 PM   #1
Join Date: Feb 2003
Posts: 70

Ok, I know, one is 4MP and one is 5MP.

My question really boils down to the numbers on the lens.

The S90 has 2,8-5,2/6-18 and a 1/2.7" CCD.

The W5 has 2,8-5,2/7,9-23,7 and a 1/1.8" CCD.

Could somebody explain these numbers to me individually as to what they mean and why one is better than another?

I"m looking for a new camera that will do well in lowe light conditions (inside, night) and I'm guessing that the W5 will be the ticket but I'm not sure why.

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Old Mar 26, 2005, 3:33 PM   #2
Join Date: Jun 2003
Location: Savannah, GA (USA)
Posts: 22,370

The f/2.8 is the largest available aperture (represented by the smallest f/stop number) at the lens' wide angle position. The f/5.2 is the largest available aperture at the lens' full zoom position.

A larger aperture (smaller f/stop number) is desirable for lower light conditions (since this allows faster shutter speeds).

A lens rated at f/2.8-5.2 is typical for a compact model.

In the case of these two models, their light gathering ability is identical.

The next set of numbers you're looking at represents the focal range of the lens (actual focal lengths, versus 35mm equivalent focal lengths).

Since these cameras use very small sensors (compared to the size of 35mm film), the focal lengths of the lenses can be much shorter for any given 35mm equivalent focal length.

So, in the case of the S90, you have a focal range of 6-18mm that gives you the same angle of view as a 39-117mm lenswould on a 35mm camera. In the case of the W5, you have a focal range of 7.9-23.7mm that gives you the same angle of a view as a 38-114mm lens would on a 35mm camera.

The last numbers you're looking at represent the size of the CCD sensor. The sensor in the S90 is smaller (1/2.7"), compared to the sensor in the W5 (1/1.8" ). That's why it can use a shorter focal length lens for about the same 35mm equivalent focal length.

As far as which one is better would depend on the conditions you're using it in (and from a light gathering perspective, they are identical). From a sensor noise perspective, I suspect that the 5MP model with the 1/1.8" CCD is a little better (but neither one of these sensors is really ideal for lower light conditions, as are any other sensors in non-DSLR models).

What kind of night photos are you planning to take?

Unless you're taking photos with a flash (and your subjects are within the flash range), you'll need to use a tripod (otherwise, shutter speeds at night will be too slow to prevent motion blur from camera shake). Your subjects will also need to be stationary if you're not using flash at night.

Keeping ISO speeds set low will reduce any noise in the image (but will require longer shutter speeds for proper exposure).

If you're going to use a flash, then shutter speeds are not as critical (because the flash burst is so short that it has the effect of freezing the action in low light, since the subjects are not properly exposed except for the short flash duration).

Again, you'll need to make sure you are within the rated flash range if using a flash in low light. With the smaller Sony models, this is usually around 12-13 feet at the wide angle end of the lens, droppng off to around 8 feet or so at the telephoto end of the lens.

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