Does temperature affect auto focus fine tuning?

[larrywilson]

The temperature has dropped well below freezing here which is unusual to be as cold as it has been for several days now. I practice my long lenses technic in my back yard and noticed that my small birds were slightly out of focus. I thought that I had everything in tune, but I had to adjust the fine tune because of front focus. The focus seems right on at this time.

I did the original fine tuning by using the automated fine tune process on a target shooting 12 times and taking an average throwing out a couple of the out liners.

This time in the cold I just shot my small birds and I like to shoot my wood fence that is just a little off line using the screw heads as a target. I finally came up with an adjusted fine tuning value that eliminated the front focus showing up.

The above statements is the reason I am asking if temperature can change the focus tuning on a camera?

Thanks

Larry

 

[Dr Bob]

In optimum conditions (concrete floor, Gitzo Series 5, shutter delay and mirror up for me) with a good for testing target I get 90% repeatability.

Your dilemma is your bird photography is not in optimum conditions.

Have a good Christmas

 

[Richard B99]

I wonder if we are seeing something similar here. In cold weather battery voltage will drop and maybe if battery voltage is at the lower end, could this be causing mushy shots with VR on at high ss? If you think about it, VR will require a fair bit of power and if the voltage is low then is there enough power for everything else?

The lesson I learnt was to keep my battery in the top 50% of charge and not to use VR with high ss. Never had the 'mushy' image problem since.

Curious, might be something in that. I do recall battery was low at the end of the day and wasn't completely fresh at the start. Yesterday's one was freshly charged.

That's interesting. Similar effect to what I saw. I never repeated the problem as I always keep my batteries at the top end so I dont loose any important shots. I wonder if this was a significant variable or just another red herring?

Yes, difficult to tell. If I had the time, I might try to test it but it gets increasingly hard to manage the variables! I think I'll stick to the basics, avoid using VR when it offers no real help and keep an eye on battery levels and swap in a spare.

Where are you shooting the kites? Up at Gigrin Farm?

No, Thames Valley and the Chiltern's. Red kites have been one of the great conservation successes and in winter, quite large totally wild groups can be seen. No longer need to go to Wales!

--
Andy

My best shots of Red Kites have come from Dinton Pastures (near Reading), our son lives near there. See link below. I always surprised driving down the M4 how many there are but never any west of the Membury services - until you get well into Wales.

Yeup, that the general area, that whole area of Winersh triangle and along the Thames there offers good views. They moved south and west (hence your Membury observation) out of the original introduction area in the Chilterns. Thames Valley is now very good. I first saw them while driving along the M40 in the early 90's. I was so surprised that I nearly lost the car - bad at 70mph. I remember emailing the BTO (no www then) and getting a very nice email back saying "yes, we have been reintroducing them for the last few years". Been enjoying them since.

They are still spreading and I notice they come further south (and I'd guess west) each year. I now see them south of the M3 where I live and that's only really happened in the last three years as that season's young distribute. Seen two in the past two weeks above our town. I'd love to think a pair would nest in the garden one day (we have a few 30m scots pine which would be perfect)!

--
Andy

http://andyburnsphotography.zenfolio.com/raptors/h6410e661#h43832742

 

[Leonard Shepherd]

On your repeatability figure. Does this mean you get a sharp image 90% of the time - ie the target plane is within the camera's 'field in focus' or is it based on tighter performance, ie the centre of the field in focus is within xx mm of the target plane? I hope I am making sense.

The camera/lens is first checked to make sure the highest lpm is achieved with nil fine tune.

Repeatability is based on no reduction in lpm recorded in a series of shots.

As noted earlier everything locked down tightly on a heavy tripod on concrete, shutter delay are rarely possibly photographing lbj's in a reed bed.