02-06-2019 09:19 AM
I have two cameras, a Canon 70d and a 5d Mk III. I also have several lenses, but my 'go to' lens is my EF 100-400 4.5 5.6 L series zoom as I do a lot of aviation photography. On each of them, I've used metering start/focus (front button) and back button focus (AF ON).
My question is thus: Why does it take several presses on the back button to achieve focus on subjects well in excess of 6.5 meters to infinity setting (ex: A bird feeder 30 feet away). Should it not take just a single press?
I sent the lens to be cleaned and inspected by a company in California about a year ago, which claimed that the lens was working properly and adjusted to 'factory specs'. This led me to believe the problem was with the Camera (70d). I recently purchased the 5dM3, and the problem persists. The batteries on both camera are fully charged, so it's not for lack of power.
Since I do not use my 24-105mm f/4 IS USM for long range photography, I cannot say if happens with that lens as well.
02-06-2019 09:55 AM
"On each of them, I've used metering start/focus (front button) and back button focus (AF ON).
My question is thus: Why does it take several presses on the back button to achieve focus"
Are you saying the same thing doesn't happen if you use shutter button focus?
02-06-2019 11:50 AM
02-11-2019 10:47 AM
I will have to re-check, but looking back, it may have been the case with the front button as well. I have never been really happy with the focus function on these cameras, as I feel that Canon camera lenses have a softer focus than others I've used.
In aviation photography of fast moving fighter aircraft, I never have the time to manually focus, so I depend on autofocus for sharp photos, and rarely is that happening.
02-11-2019 01:06 PM