05-05-2016 01:17 PM
When photographing birds with my 60D and 100 mm-400 mm zoom (orignal), AF takes several tenths of a second to complete sfter the shutter is depressed half way. I frequently wonder how much this response time depends on the camera and how much on the lens. Would just changing to the new version of the zoom speed up this response tme? I would love to hear a camera engineer to talk sbout this.
05-05-2016 01:43 PM - edited 05-05-2016 02:09 PM
Have you ever heard of "back button focus" before? You can pre-focus, and take a picture the instant you press the shutter button.
Some Canon DSLRs have different Auto Focusing systems in the cameras. The easiest difference to spot is the number and type of AF points, although most people eventually wind up going with just the center focus point. Some cameras have better performance with lens that are f/2.8, or faster, too.
The latest "dual pixel CMOS AF" system is designed for focusing on fast action. I think focusing speed is a combination of camera and lens. You already have a pretty good lens for fast focusing action. I don't think you would gain as much by going to a new lens, as you could gain by going with a new camera that used "dual pixel CMOS AF", like the 7D Mark II.
[EDIT] BTW, I am not a Canon Engineer.
05-05-2016 03:40 PM
I think dual pixel autofocus is for live view and video, when the mirror is locked up and not used. I don't think it helps in normal autofocus mode using the mirror.
05-05-2016 06:28 PM
Yes, you're correct about dual pixel.
05-05-2016 07:36 PM
FWIW I don't like nor use Back button AF but have been shooting the 100-400 for almost 10 years now & will stick with the one I have. From what I've read the new model is slightly faster at acquiring focus but AF speed is a combination of body & lens. The 1 series bodies have the fastest system & the 7D & now 7D2 are pretty close to the 1 series body of the same era but not quite the same. I shoot radio control flying events, start the AF & track for a bit before shooting & shoot in bursts of 4 or 5 shots unless I think trouble is coming. Proper use of the limit switch cuts the AF time down if you don't need the lens to focus on closer objects, & must always be set to the appropriate setting.
05-05-2016 11:05 PM
Thank you all for your inputs. Cicopo's points are particularly helpful. My question was not as much about technique (yes, I do use the limit switch), but about the capabilities of the hardware (how fast can the lens element respond, how quickly can the camera body provide the feedback signal to the lens?). I wish Canon could provide some engineering input on this type of question. bBring that, the experience of users on the forum is very helpful.
Blue-gray gnatcatcher in a local park
05-06-2016 07:01 AM
"FWIW I don't like nor use Back button AF ..."
Me too! It's a gimmick.
I am also a long time user of the original 100-400mm and an occasional user of the new model. The new one is faster on my 1D Mk IV. Is it a big deal, only you can tell if it is worth it. It isn't a lot. You need to remember the longer the focal length, the longer the focus ability has to be and the further it has to travel.
Make good use of the tips suggested above.