Trouble with Nikon Z8 autofocus with the 180-600 lens

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James C.

James C.

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I'm using my Nikon Z8 with my 9-month old, Nikkor 180-600mm lens. I sometimes have trouble with the autofocus (AF) acquiring birds quickly that are sometimes relatively stationary, and often with birds-in-flight (BIF). I often have to either zoom out, or fiddle back and forth with the manual focus ring, for it to latch onto the bird, and usually by that time, the bird has flown to far off, or has changed its position, and I've lost the shot.

I use Back button focus (BBF). I have subject detection set for birds. I have my Fn1 button set to cycle through Wide-L, 3D, and Wide-S. I'm shooting in AF-C mode with auto ISO. I used to shoot in Shutter Priority mode, but I recently have gone to Manual Mode (as things were back in my film days).

At first I thought it might be because since I shoot during the late afternoon/evening "Golden Hours" it was because the light might be low. However, I had similar problems this past weekend when photographing birds at Sandy Hook Beach here in New Jersey in bright, sunny morning, weather.

Now sometimes, with BIF, I realize with a deep blue sky, and a dark-colored bird, there might be an issue with insufficient contrast that the AF might need. But when the subject is (what I think) well-illuminated, even against a deep blue sky, should that make a difference?

I'm going through Steve's z8/z9 Guide for shooting wildlife a second time now and I just don't see what I'm doing wrong that would cause me to miss so many shots.

I'd appreciate any helpful insights to resolve this issue.

Thanks.
 
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When there are problems with AF, you can almost always try a smaller AF area choice and improve results. That has two benefits - it tells the camera where to look for a potential target, and allows the camera to process less data in searching for a target. I'd try Wide Small or a Wide Custom 1x1 box. Both provide subject detection, and both have nearest subject priority which keeps the camera from picking up the background. Area and 3D are good choices, but when they don't work - go smaller.

The other thing you might try is to help the camera recognize the AF target and subject. There are two things that can help. Make sure your subject is well exposed - or at least has adequate contrast to for subject recognition if it is being used. The other technique is to pre-focus at approximately the correct distance so the subject is relatively in focus through the EVF and can be recognized. With a long lens, it's easy to be extremely out of focus and the camera searches for a subject and then gives up. With pre-focus on approximately the right distance, the camera has an easier time finding the subject.
 
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So, the 186 is more than adequate and it is quite speedy to AF. I suspect that what you are describing is the phenomenon where a lens doesn't AF because the scene is of singular contrast and the intended target is so OOF that the camera cannot detect any subject which would cause the lens to cycle. One has to "bump" the af either with a MF twist or by pointing it at something closer with contrast. It isn't unique to the 186/Z8 but occurs with all lenses/cameras.
 
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JAJohnson said:
The 180-600 has only one focus motor and it sometimes isn’t snappy when acquiring first focus on a distant subject. Use of the focus limiter and prefocusing on the area where you expect the subject to be can help. Refer to the review by @Steve (at 35:16) for more info.

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I generally keep the focus limiter on "FULL" since sometimes a bird may pop up fairly close to me. Might I have better luck if I set it to 6m-Infinity?
 
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James C. said:
I generally keep the focus limiter on "FULL" since sometimes a bird may pop up fairly close to me. Might I have better luck if I set it to 6m-Infinity?
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I think it's less an issue of "luck" and more that of understanding how your af system and lens works. Using the focus limiter can improve performance by limiting the range the lens has to search though I don't think that's the issue you're experiencing.
 
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James C. said:
I generally keep the focus limiter on "FULL" since sometimes a bird may pop up fairly close to me. Might I have better luck if I set it to 6m-Infinity?
Click to expand...
If you’re focusing on a subject beyond 6m, it will keep the lens from hunting close to you. It can help to shorten focus speed on distant subjects.
 
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James C. said:
Now sometimes, with BIF, I realize with a deep blue sky, and a dark-colored bird, there might be an issue with insufficient contrast that the AF might need. But when the subject is (what I think) well-illuminated, even against a deep blue sky, should that make a difference?
Click to expand...
Example problem images would help with feedback.

CAUTION - AF does not detect colour as we do - it normally works in monochrome.

If a bird has a similar tone to a blue sky there may be insufficient contrast for reliable AF.
 
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Len Shepherd said:
Example problem images would help with feedback.

CAUTION - AF does not detect colour as we do - it normally works in monochrome.

If a bird has a similar tone to a blue sky there may be insufficient contrast for reliable AF.
Click to expand...
You raise a good point, Len, and it’s something to keep in mind.
 
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JAJohnson said:
You raise a good point, Len, and it’s something to keep in mind.
Click to expand...
Thanks for the compliment.

For the occasional AF "miss" - it takes just a few seconds to convert a colour image to B&W on a monitor - and to then compare the tone of the subject to the tones surrounding it.

For those who have not experimented red, yellow and green in an image converted to B&W have similar tones - though as they have different reflectance properties there is usually enough luminance difference for AF to do what we expect it to do.
 
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