Just bought....

**Rainer.** · 06-25-2008, 10:53 PM

70-300 ranges rarely come faster than f4 without getting really pricey really fast, which I find makes them quite difficult to work with indoors, so good luck with concerts.

Brent · 06-26-2008, 05:21 AM

Speed doesn't bother me as much as sharpness I guess. I can always manual focus. I need to read up on lenses somewhere with all the USM vs. DC, IS vs. non-IS etc etc etc stuff going on with lenses. I can hold my own with camera in hand and have a great eye for composition (so I've been reaffirmed), but when it comes to knowing what all the lens terminology is, it's all relatively new to me. Better to stick with Canon lenses or are the Sigma and Tamron alternatives just as good or what? Sorry to sort of change the direction of this thread some more...can take it to a new one if it bugs anybody.

**Rainer.** · 06-26-2008, 10:55 AM

Just to make sure we're on the same page, but not to insult your intelligence, when we talk "speed" in a lens, we're really talking about shutter speeds, lenses with larger apertures (smaller f values) will allow you to use faster shutter speeds (lower ISO in lower light situations), while slower lenses (most cheaper long zooms) do not have wider apertures which can make shutter speeds slower to compensate.

I know I find difficulty trying to get my shutter speeds fast enough when I use my 70-300 f4 lens.

Brent · 06-26-2008, 01:53 PM

See, that's the stuff I want to know. When you say speed I assume speed of autofocusing. I'm aware of how aperture and shutter speeds work, but I'd never heard aperture related to speed before, so I assumed it had something to do with focus. I understand the concept of larger apertures (smaller F stop values) meaning more light can get through when the shutter is open vs. at smaller apertures (larger F stops). I honestly don't know how I ever understood apertures since they seem to directly contradict logic with the larger numbers being smaller, and smaller numbers being larger.

ApparentlyNothing · 06-26-2008, 02:05 PM

Quote:

Originally Posted by Brent

See, that's the stuff I want to know. When you say speed I assume speed of autofocusing. I'm aware of how aperture and shutter speeds work, but I'd never heard aperture related to speed before, so I assumed it had something to do with focus. I understand the concept of larger apertures (smaller F stop values) meaning more light can get through when the shutter is open vs. at smaller apertures (larger F stops). I honestly don't know how I ever understood apertures since they seem to directly contradict logic with the larger numbers being smaller, and smaller numbers being larger.

Sorry about that. Sometimes I forget who I'm talking to and assume things about their knowledge. When someone just talks about the speed of a lens, they almost always are referring to what JonRainer said: larger aperture. Larger aperture means faster shutter speeds in low light. Usually when someone is talking about AF (autofocusing) speed, they specify AF or autofocus speed.

If you had a camera that had good image quality at high ISO, you could probably get away with an f4 in lower light. But the XTi is not usually considered to be that great at high ISO. Taking pictures with that 75-300 lens of mine is usually outdoors, and I get good results. If it were in a dimly lit room though, no way I'd be able to hand hold it without a flash.

Brent · 06-27-2008, 07:07 AM

So what is the significance when a lens says something like f/4.5-5.6 in its description? Why the two numbers?

tht00 · 06-27-2008, 07:37 AM

Quote:

Originally Posted by Brent

So what is the significance when a lens says something like f/4.5-5.6 in its description? Why the two numbers?

That's the maximum aperture of a zoom lens.

The first number is the maximum aperture fully zoomed out, and the second number is the maximum aperture fully zoomed in.

The f number effectively lets you know the ratio between the aperture size and the focal length. The lower the number, the larger the aperture, the more light it lets in, and the less depth of field you can get.

**Rainer.** · 06-27-2008, 08:22 AM

So when the lens is at 70mm, f4 is your widest aperture, while at 300mm, your widest aperture is f5.6, which is relatively small, compared to what you could get with, say, a 50mm prime.

ApparentlyNothing · 06-27-2008, 12:09 PM

Ditto what the rest said. They make zoom lenses that are consistent throughout the zoom so it doesn't change max aperture while zooming in or out, but they are almost always more expensive. I think there are some lenses out there that even change no matter what aperture you're at. For example, the 75-300 lens I have, if I'm at 75mm and f4, and I zoom all the way to 300mm, the aperture changes to f5.6. But if I were at 75mm and f8 and I zoomed in to 300mm, I'd still be at f8. It's only when I'm at max aperture does it change with zooming. BUT, I believe there are some lenses out there that don't do this, where zooming at f8 would change aperture the same as if you were at max aperture. It's something to look out for when buying a lens with a non-fixed aperture throughout the zoom. I think all Canon zoom lenses don't do that, but don't quote me on that.

Brent · 06-27-2008, 10:34 PM

So then...if we're not worried about starting new threads I'll keep this here...best bang for my buck lense for a Rebel XTi for around $300 or less? Keeping in mind that I'd like to have a fairly usable zoom range--think, 10th row concert tickets and I might want to get as tight as an upper half of the body shot of someone towards the back of an average size stage--balanced with the best aperture (or SPEED, I learned...haha) range. I know I can't have the best of both worlds for that price, but the best balance of the two would be nice. Doesn't have to be a Canon lens, just needs to be EF or EF-S mount.

ApparentlyNothing · 06-27-2008, 10:58 PM

Quote:

Originally Posted by Brent

So then...if we're not worried about starting new threads I'll keep this here...best bang for my buck lense for a Rebel XTi for around $300 or less? Keeping in mind that I'd like to have a fairly usable zoom range--think, 10th row concert tickets and I might want to get as tight as an upper half of the body shot of someone towards the back of an average size stage--balanced with the best aperture (or SPEED, I learned...haha) range. I know I can't have the best of both worlds for that price, but the best balance of the two would be nice. Doesn't have to be a Canon lens, just needs to be EF or EF-S mount.

Honestly, you're not going to get anything in that price range with a fixed aperture, and it will almost certainly be f5.6 at the max focal length. Here's a link for Canon zoom lenses with reviews and links to a store so you can check prices.

http://www.the-digital-picture.com/R...s-Reviews.aspx

I don't know a whole lot about any of the telephoto lenses in that range, so I can't really give you any specific advice.