Usefulness of the bird AF on shorter range lenses?

[Pat L]

I've recently acquired two new Nikon lenses for shorter range macro or landscape photos to try on my Z8: Nikon 135/1.8 Plena lens and the 24-120 f4 . Both are nice, sharp and responsive, but I have been practicing with them on my handy backyard bird feeder (about 20-25 feet away) and I have noticed that using the bird setting to find the bird eye doesn't seem to work. The AF is just as likely to settle on the feeder or anything in the general area than on the bird. I can get decent shots using Auto AF or small group settings, etc. But I am wondering why the bird eye AF doesn't work?

Perhaps the bird is too small in the image area? Longer range lenses like the 100-400 work well.

Has anyone else noticed this or have a suggestion?

I understand these aren't bird lenses but sometimes you can get close to birds and a great portrait lens would be perfect for bokeh.

 

[DRwyoming]

Perhaps the bird is too small in the image area?

That's the most likely explanation. Even when shooting long focal length lenses the eye detection can struggle when the bird is small in the frame. Sometimes switching to DX crop mode can help but subject/eye detection needs enough information to work off of and when your subject is very small in the frame subject/eye detection can struggle.

At the distances you're talking about (20-25 feet away) I'd expect most backyard birds to be very small in the frame shooting with a 135mm or 120mm lens.

I understand these aren't bird lenses but sometimes you can get close to birds and a great portrait lens would be perfect for bokeh.

I've occasionally gotten close enough for decent back yard bird shots with a 300mm lens but getting close enough with a 135mm lens would be very surprising unless your backyard birds are very large and you can reliably get very close to them. Perhaps the lenses you're talking about would be great bird lenses in some remote capture applications where you could place the camera/lens very close to a frequently used perch and remote or auto trigger the captures but for typical viewfinder photography those are pretty short focal length for most bird photography.


In terms of bokeh and soft backgrounds, longer lenses including 400mm, 500mm and 600mm or longer lenses can deliver fantastic backgrounds and excellent bokeh. Yeah, they're not typically used for human portraits due to the very long working distances involved but long telephotos are great portrait lenses for smaller subjects.