I am using the Nikon 50mm f1.8 AF lens on my D40 and the photographs look excellent - I have to manual focus, but this suits me just fine for the portrait shots I'm taking.

The problem is that to use this lens on the D40 I am forced to lock the aperture at its highest setting (even in full manual mode).

Why is this?


The 50mm f/1.8 AF will meter on the D40, it does have a chip. But it will not AF.

You have to set all[1] Nikkor lenses with aperture rings to the smallest aperture in order for Program and Shutter priority modes to work. The reason is that the camera body will set the aperture at the moment of taking the shot in these modes, and the aperture has to be in a "known state" for this to work.

The lock is simply a convenience to avoid the aperture ring moving accidentally.

If you look at Nikon's G lenses - the ones without an aperture ring - you'll notice the aperture blades are stopped down all the way when the lens is unmounted. This is the same principle at work.

It's been a while since I used the D40 but I do think you have to set the aperture on the camera body - press and hold the exposure compensation button and move the thumbwheel.

[1] all lenses confirming to the AI-s spec (including AF lenses)

  • Okay - so although I can't use the aperture ring I can use the camera controls to adjust it? I am shooting in full manual, so I will give that a go - thanks.
    – Fenton
    Feb 4 '11 at 14:41
  • Yes - I have tested this and you are spot on. I assumed that because it had a manual aperture ring, that was what I had to use, but you lock it at max aperture and then wind it to f1.8 using the in-camera setting just like you said. Thank you :)
    – Fenton
    Feb 4 '11 at 16:49

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