Knowing what Lens to use.

[digmo]

Hi all,

I have two questions I am trying to clear up.

1. I own a Sigma 24-70 F2.8 and now a Canon 15-70 f3.5 I am wondering if I really need the sigma now I have the new Canon lens ?

2. When do you know when to use different lenses. Like in the above lens what are the different circumstances where one is better than the other.

I also own a nifty fifty and under what circumstances would I favour it ?

I am still learning very slowly.


David

[inkista]

Originally Posted by digmo

1. I own a Sigma 24-70 F2.8 and now a Canon 15-70 f3.5 I am wondering if I really need the sigma now I have the new Canon lens ?

If you're talking about the Canon EF-S 15-85 f/3.5-5.6 IS USM, definitely.

The maximum aperture on the Canon is much smaller than on the 24-70 f/2.8, especially at the telephoto end of the lens. While focal lengths determine framing, and the 15-85 covers a wider range, maximum aperture determines your shutter speed in specific lighting situations, and an f/2.8 max. aperture can shoot with higher shutter speeds in lower light. While IS can compensate to a certain degree, it can only affect camera shake blur--NOT subject motion blur.

You're likely to want the Sigma if you're shooting in lower-light situations, such as inside without a flash.

2. When do you know when to use different lenses. Like in the above lens what are the different circumstances where one is better than the other.

It basically comes down to knowing the basics of the "exposure triangle": how iso, shutter speed, and aperture interact to make an exposure, and what focal lengths are going to fit your subject matter/working distance best. For example, the 15-85 is going to be a better landscape lens, if you want to go wide angle with a large vista.

I also own a nifty fifty and under what circumstances would I favour it ?

When you have the working space/distance to "zoom with your feet", when you want to have a large amount of background blur, or in lower light situations (again, down to a larger max. aperture). It's also smaller and lighter than either of the other lenses, so if you want to travel light, it might also be a better choice.

[digmo]

Thanks

So the Sigma would be good for music / gig type photos whereas the Canon would be a good general out and about lens.

I have much to learn

David

[inkista]

Originally Posted by digmo

So the Sigma would be good for music / gig type photos whereas the Canon would be a good general out and about lens.

Yes, although the 50/1.8 might be the best for the stage shooting.

The difference between f/2.8 and f/2 is one stop, which is a doubling of the light. Exposure-wise, that's the same as going from iso 400 to iso 800, or from 1/50s to 100/s. If you have the 50 f/1.4, f/1.4 is two stops more than f/2.8. That would be like going from iso 400 to iso 1600, or 1/50s to 1/200s.