Will this ef lense work on a 7d?
 

will this lense work with my 7d? will it cause vignetting?

also what would it be in equivilant on a crop 1.6 aps-c senor?

cause i found one local new for 125...

thanks

http://www.bhphotovideo.com/c/product/169267-USA/Canon_6473A003AA_75_300mm_f_4_0_5_6_III_Autofocus.html

Yes, it will work.

No, it will not cause vignetting.

What you won't be able to is zoom in or out and maintain either exposure or focus. You need a par-focal lens with a constant aperture.

As for the crop-fator, you've answered your own question; 1.6

i found this locally is this a better choice? i found this locally for 200 bucks picked up...

i was reading and it said when used on a crop 1.6x eos, its equivalent to a 43-465mm...

i was just wondering if this would keep constant or close aperature, and focus...

Tamron | Zoom Wide Angle-Telephoto AF 28-300mm | AF061C700 | B&H

all zooms with a constant aperture = par-focal lens?


Daniel

When you see two f numbers on a lens then it is not a constant aperture, so f3.5-5.6 has f3.5 at the widest angle and f5.6 when in full telephoto magnification and in the mid range of focal point, could be something in between those numbers.

The trouble when filming and zooming the video will seem to flicker as the aperture starts to change automatically as you zoom.

I'll go out on a limb and say that any zoom lens you find used for around $200 to $300 won't be a constant aperture.

No.

I have two L series f4 lenses. The 17-40mm f4L seems to hold the same focus through it's zoom range while the 70-200 f4L does not.

No. A parfocal lens is a lens that holds its focus even as you zoom it.

Parfocal lens - Wikipedia, the free encyclopedia

Corey,

Look like you're pretty new to this whole DSLR business, like many of us here on DVinfo.

Here ar two short articles that I think are a good read for people new to SLR's and lenses:

Looking for Canon SLR lenses?

Best Canon lenses to buy on any budget

And here a very long read for people that want to know more:

Canon EOS Beginners' FAQ III - Lenses

i was looking on a tamron 185d but i think its old....

what about this?

AF016C Tamron SP AF 17-50mm f/2.8 XR DI-II LD Aspherical (IF) Standard Zoom Lens for Canon EOS, 6 Year USA Warranty

Heard some pretty good things about that one, although if you plan on shooting a lot of video with your 7D you might want to consider a lens with image stabilization (VC for Tamron, IS for Canon and OS for Sigma). Without (image) stabilization it is very hard to produce any watchable material shooting handheld.

There is a VC version of this Tamron lens you mentioned, the downside is that the non-VC version outperforms the VC version on pretty much every aspect. For a more detailed comparison see Canon Digital SLR Camera & Lens Reviews

Bill,
Are the 15-55 2.8 and the 70-200 2.8 considered parfocal? I have both. but assumed that focus drifts as you zoom. I'll try focusing at full tele and then see if they mainytain at wide and vice versa.
Bruce Yarock

2044B009AA Canon EF-S 55-250mm f/4-5.6 IS Image Stabilizer - Refurbished


is this a good choice?

Corey I would advise you to read the 3 articles I posted earlier and besides that read a lot of reviews on Canon Digital SLR Camera and Lens Reviews at The-Digital-Picture.com

The Canon EF-S 55-250 is a low end consumer lens and will be more than good enough for some, but frowned upon by others. Im my opinion there a 3 true statements when it comes to lenses:

1. You generally get what you pay for
2. It is worth saving up and investing since a good lens can stay with you for life
3. The faster (the lower the number behind the f/) the lens the better

If any I would much prefer the Tamron above the low end Canon you just posted, but they are two totally different lenses with their own uses.

alot of people say the tamron 17-50mm f/2.8 xri, is this sharp?

edit:will follow focus make the video smoother with the tamron 185d lense that doesnt have image stabilization?