How do I know if my lens is to slow/fast?

[avdh20]

Ok I am a Newbie to this site, and by reading the threads everyone here seems pretty helpful. Im also new at this whole SLR thing too, considering I just purchased my 20D a month ago. Anyway I've been reading some threads and noticing that people say that their lenses are to slow or to fast. In that case they are needed to use a flash. What does that mean, when they say their lens is to slow? Dumb question, i know. But I'm just trying to learn. Thanks.

[pcasciola]

Slow lens = small maximum aperture, like f/5.6 or higher, requiring slower shutter speeds
Fast lens = larger aperture, like 1.8 or 2.8, allowing faster shutter speed

[Ogrt48]

Oh and both of those lens you have are slow. :D

[HJMinard]

Basically ... a slow lens is less useful in low light conditions without the use of a tripod.

From a performance standpoint, I don't think a lens can ever be "too fast". However, fast lenses are often quite large, heavy and expensive.

[Sydor25]

From a performance standpoint, I don't think a lens can ever be "too fast". However, fast lenses are often quite large, heavy and expensive.


Except for the 50mm f/1.8. It is worth every penny and then some. Do yourself a favor and pick one up, it will be the best $80 you've spent.

[avdh20]

Thanks for the replys-What lenses would you guys/gals suggest buying? I just ordered the 50mm 1.8 from B&H so that should be here Tuesday. I really hate my 75-300 and im looking to trade that in for the 70-200mm L lens.

[pcasciola]

It's impossible to recommend lenses without knowing what you are looking to use them for, but the 50/1.8 is always a nice-to-have, and the 70-200/4L is arguably the best bang for the buck L lens there is. For me it's a tough choice between that and the Sigma 70-200/2.8 EX HSM for a lens covering that range in the $600-700 range.

Have a look here:
http://photography-on-the.net/forum/showthread.php?t=56752

[liza]

The 100mm f/2 is a pretty decent lens, too, and isn't prohibitively expensive. The Tamron 28-75 f/2.8 isn't a bad lens either from what I've heard. I'll probably get that one next, although the 85mm f/1.8 is also tempting. Like Phil said, it's difficult to give advice if we don't know what you're planning to shoot.

[avdh20]

I guess you could say that I shoot it all. It doesnt matter what it is, I just love taking the pic. So what ever you all suggest is prob. what im gonna buy. To start, maybe a good lense for low light applications?

[liza]

The 85mm f/1.8 is a good lens for both portraits and sports (especially basketball!). The 70-200 f/4L is an awesome lens with excellent color, although it isn't considered "fast." Most people who shoot fast action or in low light conditions opt for the 70-200 f/2.8. I'll have to save for a while to get that one!