F100 Light Metering AF vs AI lenses

Discussion in 'Nikon' started by gustavoquintela, Oct 26, 2017.

  1. Hello everyone,

    I just want to clarify one point regarding the light metering of the F100 with a AI lenses.

    I recently acquire a Nikon 50mm f2.0 AI lens, and I notice that when using A mode the shutter value given is completely different when using the AF lens. I tested both lenses with the same settings, center weight metering, aperture priority mode and aperture set to f2.8.

    I know that the AI lenses have no CPU, but since the manual of the F100 say that is possible to use the aperture priority with AI lenses, I am finding strange, that with such similar lenses, I have really different values of the shutter.

    Is this normal? If so, why?

  2. How much of a difference are you seeing?

    It may just be a matter of the f/2 not transmitting light as efficiently. Modern coatings help this, and problems like haze and fungus that can appear on older lenses will hurt this.

    You'll often see Cinema lenses marked in "T stops", which reflect the actual light transmitted by the lens. I've gone to the trouble of measuring this on some large format lenses, although it's applicable to any format.
  3. If you set your camera to matrix metering then there will be a difference as the F100 automatically switches to Center Weighted mode with AI lenses.
  4. Thank you guys for the help.
    I already figured it out what is the problem. Is related to the Aperture ring coupling of the F100.
    Basically when the lens is mounted and I set the aperture ring to, for instance, f16, and I move back to f2.8 this plastic aperture ring doesn’t follow the aperture ring of the lens. That was why that the camera was giving stupid different values of the shutter, because I though that the aperture was at f2.8, but in fact the the plastic ring of the F100 was at f16.
    I forced the position of this plastic tip with a piece of paper and I set it to the correct f2.8 position, and after that the meter reading was matching with the one with the AF lens.

    If there is no lens mounted, the ring moves freely, and seems to be ok. But when I mount the lens, gets stiff, and don't work properly.
    Do anybody know if this is a easy fix? I could send it to the Nikon repair service, but I am afraid that they will charge me more for what I paid for the camera.

    Well, at least now I know what is the problem now, it was driving me crazy.
  5. Is your AI lens factory AI, or was it done by milling the aperture ring?

    If the tab moves freely with no lens mounted, I would think the problem is that the tab is fouling on the lens.

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