Lens with variable aperture

jennievii

Do you find it's worth it to spend the extra money on a lens that doesn't have a variable aperture? I'm interested in getting one that is f/2.8. I'm trying to use manual settings more than I used to, so I'd imagine it can get very frustrating to have to keep changing the aperture just because you zoomed in a little. I'm most likely going to be purchasing the Canon 50D and am trying to decide what lens to get for it.

divamum

I suspect it depends on the kind of shooting you intend to do, but speaking for myself I'd say a fixed - and ideally FAST - max aperture is DEFINITELY worth the extra, especially since it's often not that much extra (I'm another fan of the Tamron 17-50. Don't know if I have an excpetional copy or what, but it is beyond sharp - rivals the 50mm 1.8 from about f4, and isn't much different wide open - mine is a reliable focuser even in the dark, it's light and I picked up all that qualitylike-new for an absurdly low price via Craigslist).

I have to say that when I can finally upgrade the long end of my zoom lineup, I will FOR SURE be looking for a fixed, fast maximum aperture. Suits my shooting style, my subjects and makes life easier all round. In the meantime, I find myself drawn to tele primes instead....

amg2833

I'm right there with ya'. I love my Tamron 17-50 2.8. I think fixed aperture is completely worth it, especially if you're often in manual. Even aside from that, you'll at least a stop (or more depending on what lens you own) more light. Wahoo!

ziggy53

Modern cameras will adjust the exposure to compensate for a variable aperture lens in most of their modes of operation. The bigger problem is that most variable aperture lenses, at least compared to "constant" aperture lenses, are generally of less optical quality.

Please do some comparison reviews at the following sites:

http://www.slrgear.com/
http://www.ephotozine.com/
http://www.photozone.de/
http://www.eospix.com/
http://www.photodo.com/products.html
http://wlcastleman.com/
http://www.zen20934.zen.co.uk/photography/LensTests/index.htm
http://www.lensplay.com/

Compare lenses of similar focal length and range in both constant aperture and variable aperture design. The constant aperture lenses, by design, are consistantly better in almost every case.

ziggy53

I should also add that "larger" aperture lenses, forgetting the constant vs variable arguments for the moment, are almost always a benefit in other ways too.

The AF is almost always faster and more accurate with a large aperture lens vs a smaller aperture lens with otherwise similar AF motor design, etc. This is partly because the larger aperture allows more light to hit the AF sensor, but it is also because the larger aperture yields a larger difference in reference signal for the phase detect component of the AF sensor to work against. This is partly because of the reduced DOF which provides a greater sensitivity to differences in the subject features.

Read more here:

http://en.wikipedia.org/wiki/Autofocus

jennievii

ziggy53 wrote:

Modern cameras will adjust the exposure to compensate for a variable aperture lens in most of their modes of operation. The bigger problem is that most variable aperture lenses, at least compared to "constant" aperture lenses, are generally of less optical quality.

Please do some comparison reviews at the following sites:

http://www.slrgear.com/
http://www.ephotozine.com/
http://www.photozone.de/
http://www.eospix.com/
http://www.photodo.com/products.html
http://wlcastleman.com/
http://www.zen20934.zen.co.uk/photography/LensTests/index.htm
http://www.lensplay.com/

Compare lenses of similar focal length and range in both constant aperture and variable aperture design. The constant aperture lenses, by design, are consistantly better in almost every case.

Wow, thanks! I definitely have some reading to do now!