Troubleshooting 300mm f/4 PF

Over a week ago, I was out shooting eagles with my Nikon D7200, 300mm f/4 PF, and a Nikon 1.4x teleconverter. I switched between Aperture Priority (which is set as AF-S) and U2 which is BBF and AF-C. The reason I switched back and forth is due to trigger thumb in my right hand. BBF isn't always easy or comfortable with the bending limitations of my thumb.

Initially everything was fine until I noticed a problem while in Aperture Priority. At some point, I simply couldn't achieve focus in Aperture Priority, yet when I'd switch to U2 with BBF, the focus was quick and snappy.

So while troubleshooting, I mounted my Nikon 70-300mm VR lens. Everything worked fine in both Aperture Priority as well as in U2 with BBF. Then I mounted just the 300mm f/4 PF (no teleconverter) and tried out both. There was a slight lag when focusing in Aperture Priority but a quick response with BBF in U2. Then I added the 1.4x teleconverter. It finally seems to be working okay in both Aperture Priority and U2 with maybe just a slight slower focusing ability while in Aperture Priority. And during my testing, I focused on stationary subjects.

What might cause this? It obviously isn't the lens since it works flawlessly with BBF. And I didn't notice any inadvertent changes to my settings. I even toggled the switch on the lens between FULL and 3m to infinity without any apparent differences when in either Aperture Priority or U2 with BBF. Any ideas of what might have caused this? Any suggestions on what to try or to look for if it happens again?

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Thought the 1.4 was only one stop loss which shouldn't be a problem for the 7200 on the middle points.

The teleconverter is only 1-stop loss of light. The largest aperture is f/5.6 with the teleconverter. But apparently I didn't explain this well enough.

When the camera is set for BBF with the shutter button only actuating the shutter, the AF is snappy (quick and locks successfully). Press that back button, and the AF engages quickly. However, when I'm in Aperture Priority, the shutter button is set to both AF as well as actuate the shutter. Press the shutter button halfway, and the AF struggled. The lens focused to its end then didn't move. No AF lock was achieved. Just a blurry view inside the viewfinder. The only difference was the button used for autofocusing. What could possibly make it do that?

They can be silly at times, yesterday i turned my D500 on and thought what is that large rectangle in the viewfinder, it was on 1.3 crop, looked in the menu and 1.3 crop was selected, i never did it.

Originally Posted by nickt

Are focus area modes and servo modes set exactly the same between your shutter button aperture priority and bbf U2 settings? I lost love for U1 U2 a long time ago. I continually miss SOMETHING when I save settings. Always. Never fails. It might be a tiny detail, but I always overlook something between U modes and regular modes. I just use my U's for basic settings these days. I'm a full time user of bbf now. My U2 is basic shutter button focus in case I hand the camera to someone and U1 is my bigfoot setting. Just basic bbf settings that will get me a shot under pretty much any panic condition in case something really cool surprises me while I am not ready. I don't do any regular shooting under the U's. That's my U story/rant, lol.

Compare your aperture priority shutter button settings carefully with your U2 settings. Check that focus area and focus servo are set identically. That is, match area modes like single point, d9, etc and servo modes af-c and af-s. Compare everything in the 'a' menu. Compare closely, especially menu a3 and a4. For a3, check that both are off or both set to the same level. A4 will likely be different as it MUST be ON for your shutter button mode and it SHOULD be off for bbf. (leaving a4 ON with bbf will keep shutter and bb both active for focusing). I don't think a4 should matter to your issue, but maybe. Also remember that bbf with af-c on the d7200 gives you release priority regardless of a1 setting. So your comparison with shutter button aperture priority should be with aperture priority on af-c and with a1 set to release priority.

I will take a look specifically for A3 and A4 to see if there are any differences. Thank you so much for the info, Nick.