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Last night I had some problems with the AF assist light of my D80 that made me miss some pictures. I thought it would be defective, although I was able to use it the previous time. Looking for the reason, I found two posts mentioning that (in most modes) the light only works with the center AF point selected.

Is there any technical reason for that (I'm thinking perhaps of sensitivity), or is it the usual limitation of lower-end models?

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It's not so much sensitivity as coverage. The AF Assist beam is not particularly wide (even when your fingers and the lens itself aren't in the way), and on the D80 there are a lot of lenses (anything wider than about 30mm) that will put the not-centre AF points outside of the beam's coverage area. (Of course, if you're using a large-enough lens, the AF Assist beam on the body is mostly going to be illuminating the lens barrel rather than your subject anyway, but...) In other words, it's Nikon's way of telling you that "this probably won't work".

  • I get your point, but I would rather have it flashing and not focusing, than not going on at all. Besides, I was using the off-centre focus point to make portraits, that's why I found it odd – clabacchio Nov 8 '14 at 14:03
  • Think of it from Nikon's point of view, not yours. It's a lot easier to say "it only works with the centre AF point" than to say "well, sure it works with your 85/1.8, but you can't expect it to work with your 24mm lens at all or your 300/2.8 at the left side of the frame, now can you?" – user32334 Nov 8 '14 at 14:32
  • Any idea if it works with a larger AF assist light from a flash? I can use any AF point while using the assist beam on my 5D Mark iii and a 600EX-RT, but it also projects a very large flash assist grid. – AJ Henderson Nov 10 '14 at 15:08

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