topic Re: Developing Focus Delay/Failure 300mm f/4 L IS in EF & RF Lenses

Developing Focus Delay/Failure 300mm f/4 L IS

digiquisitive — Tue, 24 Mar 2015 18:01:47 GMT

This lens is very sharp, but is progressively refusing to start focusinig until I "kick start" it by manually rotating the focusing ring to an approximate focus point, then it will wake up and start focusing correctly. Happens infrequently, but increasingly, and whether lens is set to focus starting at 1.5 or 3 M distance, and regardless of whether IS is on or off. I have had the lens about 5 years, use it very often with 1.4X teleconverter, with excellent quality, on my 7D (original, not MarkII). Suggestions?? Anyone else having this problem? I have set CFn III-04 both ways, and it seems to make no difference. Neither does changing the AF patterns, nor anything else I have researched. Thanks

Re: Developing Focus Delay/Failure 300mm f/4 L IS

ebiggs1 — Wed, 25 Mar 2015 14:59:51 GMT

I have that lens. Great lens!

You need to try the lens on a different body. You don't know if it is the lens or the camera. But it sounds like the motor is giving up.

Re: Developing Focus Delay/Failure 300mm f/4 L IS

prentz — Thu, 26 Mar 2015 00:15:13 GMT

I just had mine serviced (for no fee! Thank you VERY much Canon CPS) after I was getting 'Lens Error 01' very often with my new Canon 7d MkII. Canon patiently tested and retested and finally found- the internal power diaphragm assembly was faulty and replaced. I was beginning to think my fairly new 7d MkII was the fault but it worked perfectly yesterday- no errors. If you decide to send it in, I'd suggest both lens and camera go in, just to be sure it is the lens.

And you're right, great lens- one I selected about the same time you got yours- because of its ability to focus much closer than any of the other options at the time- and had IS.

Re: Developing Focus Delay/Failure 300mm f/4 L IS

digiquisitive — Thu, 02 Apr 2015 06:04:56 GMT

Thanks very much for the reply. Hope it is not a lens failure on the way. I wondered, when Canon first brought out all of this wonderful AF drive-motor-in-lens technology, what the average mean time to failure might be -- perhaps I am about to find out for myself with this lens. I'll have to take the lens into a local camera shop to try it on a different body -- although a Canon-only shooter for the past 50 years, I still own only one body that accepts EF lenses!

Re: Developing Focus Delay/Failure 300mm f/4 L IS

digiquisitive — Thu, 02 Apr 2015 06:09:06 GMT

Very nice shot!!! Thanks for the good info, prentz. I am not a member of CPS, as you can guess from my previous response to ebiggs1. I've never experienced any kind of lens error message on my 7D, but will gratefully take ebigg1 and your advice about trying the lens with a different body (when I can get next to one!).

Re: Developing Focus Delay/Failure 300mm f/4 L IS

digiquisitive — Fri, 25 May 2018 02:54:13 GMT

I now own two (2) 7D MarkII bodies, and the lens focuses the same with both of them, as described in my 2015 initial comment.s.

Re: Developing Focus Delay/Failure 300mm f/4 L IS

Talisman — Sat, 09 Jun 2018 13:25:31 GMT

I gave up worrying about the MTF for lenses as there really doesn't seem to be any rhyme or reason to it. I've had 3 Y/O lenses fail while 20 Y/O lenses still perform well.