??? Sigma 50-500

I was considering this lens at 500mm it is 6.3 will my 7D AF on this it is only good to 5.6
My guess is AF would be slow.

Yes your 7D will AF with this lens. I've been using it on a 20D and 40D for years with no problems. I've been able to capture hummingbirds in flight so AF can't be too bad.

fishyone wrote in post #16090764
Yes your 7D will AF with this lens. I've been using it on a 20D and 40D for years with no problems. I've been able to capture hummingbirds in flight so AF can't be too bad.

Thanks for the reply I can pick up one of these cheap I may try one.
Reviews say it is soft at the edge but with a crop camera you won't see the edge.
Will yours get a sharp image at 500mm or do you need to shorten it some.

Mine has always been sharp from 50-500.

Here's one of my hummer shots taken with a 20D.

Yep; it'll AF just fine. The cutoff for AF on the Canon bodies is f/8, so it doesn't get cut off.

I have the older generation 50-500 without image stabilization. Good results on a 30D. I also have the 2x extender but never use it as it really requires a tripod in my experience and that just doesn't work in motorsports which is my main interest.

fishyone wrote in post #16090854
Here's one of my hummer shots taken with a 20D.

and one using the 1DIII

Looks nice I have a 1D mkIII but I usually keep it on my 600L.
I think I could hand hold the Sigma people talk about it being large you should try the canon 600F4 with a TC on it. It is about twice the weight of the siggy.
The one I was considering is a older one without the OS probably would need good light for it to work good.
I may give it a try if I don't like it I can always sell it.

Snydremark wrote in post #16090873
Yep; it'll AF just fine. The cutoff for AF on the Canon bodies is f/8, so it doesn't get cut off.

This is inaccurate, most canon Bodies will not AF past f/5.6

The reason the SIGMA works with ALL Canon bodies, including the majority that can not AF past/8, is it tells the Camera AF that it is actually f/5.6 (it lies )
This coupled with the lens specific design allows the lens to function as if it were an f/5.6 at the long end.

This has no effect on exposure, which is based on actual light the meter reads, with no bearing on what the lens aperture claims it is set to.

CyberDyneSystems wrote in post #16091103
This is inaccurate, most canon Bodies will not AF past f/5.6

The reason the SIGMA works with ALL Canon bodies, including the majority that can not AF past/8, is it tells the Camera AF that it is actually f/5.6 (it lies )
This coupled with the lens specific design allows the lens to function as if it were an f/5.6 at the long end.

This has no effect on exposure, which is based on actual light the meter reads, with no bearing on what the lens aperture claims it is set to.

Then why the hell don't canon do this.
I guess they want to sell more 1D series cameras.

"The reason the SIGMA works with ALL Canon bodies, including the majority that can not AF past/8, is it tells the Camera AF that it is actually f/5.6 (it lies )
This coupled with the lens specific design allows the lens to function as if it were an f/5.6 at the long end."

True. I sent a 150-500 to Sigma to have checked out because of inconsistant/inacurate focus. It checked out "within spec." I spoke with the tech working on it, who told me "after all it's a 6.3 lens, focus can be hit or miss."

I understand the 50-500 is a much better lens.

CyberDyneSystems wrote in post #16091103
This is inaccurate, most canon Bodies will not AF past f/5.6

The reason the SIGMA works with ALL Canon bodies, including the majority that can not AF past/8, is it tells the Camera AF that it is actually f/5.6 (it lies )
This coupled with the lens specific design allows the lens to function as if it were an f/5.6 at the long end.

This has no effect on exposure, which is based on actual light the meter reads, with no bearing on what the lens aperture claims it is set to.

Do you have a source on that? I've always, actually, been curious to know whether the logic is "above f/5.6" or "f/8 and above", but I've never seen any documentation; I just figured it was "f/8 and above" in order to not mess with oddballs like the Sigma, or the Tamron 18-270, etc.

CyberDyneSystems wrote in post #16091103
The reason the SIGMA works with ALL Canon bodies, including the majority that can not AF past/8, is it tells the Camera AF that it is actually f/5.6 (it lies )
This coupled with the lens specific design allows the lens to function as if it were an f/5.6 at the long end.

I have the 150-500. When racked all the way out and aperture wide open my camera bodies (6D, 7D & T3i) indicate f/6.3. I find it hard to believe that the lens is telling the camera that it is both an f/5.6 lens and that it is stopped down to f/6.3. The more reasonable assumption in my mind is that Canon does not have a hard f/5.6 shut off but allows f/6.3 and possibly more in their bodies.

In answer to the OP, my 150-500 focuses fast and accurately with my 7D body. The 50-500 OS is very similar so I would expect the same results.

Beachcomber Joe wrote in post #16092422
I have the 150-500. When racked all the way out and aperture wide open my camera bodies (6D, 7D & T3i) indicate f/6.3. I find it hard to believe that the lens is telling the camera that it is both an f/5.6 lens and that it is stopped down to f/6.3. The more reasonable assumption in my mind is that Canon does not have a hard f/5.6 shut off but allows f/6.3 and possibly more in their bodies.

In answer to the OP, my 150-500 focuses fast and accurately with my 7D body. The 50-500 OS is very similar so I would expect the same results.

I believe you are right I tried a canon 1.4 TC on my 100-400 and my 7D tried to auto focus.
Problem was it could not lock on it would get in focus but keep hunting not locking onto the target but it sure did try.
This would indicate that it don't have a hard cut off but reliable focus is limited to 5.6 unless I use my 1D then it works at F8

Black Bart wrote in post #16091208
Then why the hell don't canon do this.
I guess they want to sell more 1D series cameras.

I don't think their motives are all that sinister. Canon wants to avoid people complaining about crappy AF performance.

The slower the lens mounted to the camera, the worse the AF will perform. Canon has designed and sells AF chips that they feel work acceptable down to about f/5.6. They feel that the performance would not meet most people's expectations at f/8, so the software diables autofocus when a lens/TC combination slower than f/5.6 is mounted.

Of course, the software only works when the lens reports the correct maximum aperture. The 50-500 reports itself f/5.6 even though it is 1/3 stop slower. And f/6.3 is so close to f/5.6 that this lens generally works OK in decent light.

Some non-reporting TC's will result in bigger errors. You can try these out (or just tape the pins) to see just how good (or bad) the AF really is with combinations slower than f/5.6. In my experience the AF does get pretty bad with f/8 combinations, especially with AF points off the lens axis. f/11 is close to useless.