Zoom lens? F 2.8 with Constant Aperture

O

Omar67

Active member
Greetings,

I hope everyone is doing well during this holiday week. I have a Canon 7D and i have noticed that the camera drops down several stops (2 stops) when i zoom in. I was told that was due to the fact that i do not have any lenses that have a Constant Aperture. One of the many reasons, i purchased the camera was to shoot in a) low lighting situations and b) shooting images with a shallow depth of field. I have many zoom lenses that go 18 to 55mm and 55 mm to 200mm. I would like to get one lens 28mm or wider that can zoom to 55mm or closer that has an fstop of 2.8 (or lower) for run and gun low light shoots. Of course here is the kicker.

I don't want to spend an arm and a leg for this zoom lens. Is there anything cheap out there (Sigma etc.) that can achieve this. Also will the Constant Aperture feature (most online lens shopping does not list if it is or not constant aperture) truly stop the issue of closing down when i zoom in?

Thanx,
:kiss:
 
It's pretty easy to tell which lenses are "constant aperture" and which are not. When you look at the specs for a lens, and it says the maximum aperture is "f3.5-5.6" that means it is not constant. If it says "f2.8" then it's constant.

If you're budget challenged, just get a faster prime lens (like something in the 28-35mm range).

In a zoom lens, you can have cheap, you can have fast, but you can't have both.
 
ahhh now i get it :) okay. I guess this is a Ebay/Garage sale search. :) If anyone knows of a website that sells used lenses, please link away.

Thanx again.
 
david335 said:
The only inexpensive option is the tamaron 17-55 2.8. I think it is around $500.
Click to expand...

I personally have the Tamron and it is an excellent lens for a very good price. (around $400 street) The auto-focus if you use it is pretty loud, though. If you're shooting videos using manual focus, it really won't be a problem since manual makes no noise to begin with.

Make no mistake, though, as a stills lens, you're giving up some of the conveniences of full-time-manual (the ability to adjust focus manually without flipping the auto/manual switch) and the build quality is not all that great. There's also no image stabilization, but in terms of value-for-dollar, I don't think there's anything out there that can beat it. If you do need image stabilization, Tamron has a stabilized version (they call it VC) for about $200 more.
 
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