Today I discovered that my Sigma 150-600mm was taking a long time ( > 1s) to signal its readiness to my (Nikon D7200) camera. Neither checking settings to ensure exposure delay wasn’t set nor changing the battery altered this behaviour. Again, changing the focus range switches (which I normally don’t change) on the lens barrel made no difference. Shooting a burst was fine - after the first exposure finally happened.
When I went back to the other lens I had with me (and which I had started shooting with) all was fine.
Why would AF for a particular lens go from super-quick to painfully slow? The focus motor seems to be working as zappily as ever.
Thank you for the tip. However I just mounted the lens in question again and it is now fine: go figure! Using manual focus to force the lens to re-focus and it is gratifyingly quick across the whole focus range.
I can only surmise that though the bayonet mount was clicked, a small piece of foreign matter did prevent reliable contact for at least one of the pins.
Apologies for the interruption; we now return you to your regular programming!
I have often seen lenses not clicked fully into place. This usually is evident as – for the aperture setting. Dirty contacts can be cleaned with a clean pencil eraser if that is the problem. Glad it is working for you again.
Pro-Tip: If you haven’t used a camera and/or lens for some time, just twist it back and forth in the bayonet a few times with the lens release button fully pressed. This cleans the contacts. Even gold can put on some residue, in German often called “Flugrost” even it isn’t that.
If that doesn’t work, the next step is using a Q-tip with some isopropyl alcohol. Lot’s of people know and own that stuff from the corona epedemic when disinfectants were hard to come by. A little bottle will get you a long way and it is awesome to clean anything technical from almost any residue.
There are some magic liquids out there to clean contacts but I never even came close to wanting to use them.
