Xf 500mm infinity focus

[David Webster]

I was hoping to get some info on how to infinity focus the xf 500mm.  I’m trying to focus on distant birds in the sky.  Is there an infinity mark on the lenses? If so, I can’t find it. If there’s not one, how would one work around this?

[Astigmatism]

I've wondered the same thing. Years ago I learned that some very long lenses can focus slightly past infinity, for the reasons that temperature and other variables can move the mechanical location of infinity focus around a little bit, and IIRC using IR film can require focusing out further than the position that's best for visible light.

I've focused on birds on distant towers, and the autofocus worked for that. Still, I'll be watching this thread for further developments.

[pw-pix]

It'd be a bit of a rigmarole, but maybe enable the function buttons on the lens, focus on infinity (distant tower/tree/mountain/etc), then set that as a focus preset. Use a function button to return to that infinity focus when you have a bird against a clear sky.

I have the same problem with my XF 150-600, so far I just put up with it, or zoom out enough to find and focus on the bird, or focus on a distant treetop etc.

[BobJ]

Modern cameras rely on autofocus or assisted manual focus entirely. There is never a reliable mechanical infinity focus stop. This makes the lenses easier to design and manufacture. Forgive me, but in my opinion, what you are trying to do must be near impossible. You have the equivalent of 750mm full frame. How do you even get an erratically moving target in the viewfinder? Also you will find that the results will depend on how still the air is.

 

[BobJ]

You could select the continuous autofocus to set 4 for suddenly appearing subject and the subject detection setting to birds. I will be interested to see how you get on.

[David Webster]

15 hours ago, BobJ said:

Thank you Bob! (and all others who weighed in).

These explanations have been clear and most useful.  I now understand things much better.  I tried the continuous focus set to 4 with my subject detection and the largest focusing area with Much better results.  I thank you kindly for the info!

 

Edited September 27, 2025 by David Webster

[David Webster]

Thank you Bob! (and all others who weighed in).

These explanations have been clear and most useful.  I now understand things much better.  I tried the continuous focus set to 4 with my subject detection and the largest focusing area with Much better results.  I thank you kindly for the info!

[jerryy]

A little late to the discussion, but in addition to the reasons listed by @Astigmatism, hard stops at infinity might wreck the lens. Those mechanisms are big and “heavy”. If the autofocus motor is pushing it at full speed when it hits the stop, things could… well… go awry. So it safely coasts past the usual endpoint before heading back in the opposite direction.