how smart is my new 10D -- constant aperture lenses still wo

[gordeaux]

Is a constant aperture zooming lens worth the extra $ when used with a 10D? Or is the 10D smart enough to compensate. Or can it only compensate in some situations? (I'm pretty new to photography, as I think you can tell from this question).

The F/2.8 28mm-70mm lens costs quite a bit more than the F/2.8-5.6 28mm-80mm lens.

Will I notice the difference with a 10D?

[Cal Maier]

The difference is like night and day! The extra value of the constant aperture zoom is due to the quality of the glass used in order to accomplish the 2.8 aperture through the zoom range of the lens, and still retain an acceptable level of sharpness.

It is the lens that takes the picture, the camera just helps record that image on whatever media it is designed to use. There is no "free lunch" when it comes to lens quality, although there are some lenses that give exceptional results given the cost. ie. Canon 50mm f/1.8.

Cal

[teddynet]

gordeaux wrote:
Is a constant aperture zooming lens worth the extra $ when used with a 10D?

Depends on what you use it for and how much you can afford.

Or is the 10D smart enough to compensate.

If you shoot in Auto or Program then any camera will compensate, in Manual mode you'll have to adjust the shutter speed whenever you change focal length, but only if you set an aperture less than the f/5.6 when at the wide angle end. If you set f/8 for example then zooming in and out won't change the aperture that you have selected, so no compensation is required.

Or can it only compensate in some situations? (I'm pretty new to photography, as I think you can tell from this question).

Apertures are relative to focal length, f/4 literally means focal length divided by 4 and this is the physical size of the aperture: 100mm @ f/4 has an aperture of 25mm. This is why some zoom lenses have variable minimum f numbers, as you zoom out you're increasing f disproportionally to the increase in the physical size of the aperture, therefore giving you a new RELATIVE aperture.

The theory goes that a 100mm lens with a 25mm aperture is going to allow the same amount of light to reach the 'film' as a 50mm lens with a 12.5mm aperture, or a 400mm lens with a 100mm aperture. This explains why long, fast lenses have such huge front elements.

The F/2.8 28mm-70mm lens costs quite a bit more than the F/2.8-5.6 28mm-80mm lens.

Will I notice the difference with a 10D?

I can't see a f/2.8~5.6 28-80mm lens in my catalogue, most of the cheaper zooms seem to be f4~5.6 which sounds more likely. The one thing I do notice about the 28~70mm f/2.8 zoom if the filter thread of 77mm. This is going to be the thing you notice most for two reasons:

1) The cost of the filters is going to cripple you.

2) You're going to suffer from lens flare very easily.

The faster lens is almost 5 times the price as well, get the f/4-5.6 and spend the money you save on a tripod and a nice fast prime lens for low light work, the standard 50mm f/1.8 works out at 75mm with the 1.6X factor which will give you a really nice, fast portrait lens and is pretty cheap.

Rich.