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T-mount lens

edited May 2015 Posted in » Nikon D5100 Forum
My girlfriend has a Nikon D5100. I ordered her a Tamron 500-1000mm auto focus lens. When connected to the camera, the camera does not register lens.


  • edited May 2015
    What is the message it gives? If it is a Nikon autofocus lens with a manual aperture ring, the aperture ring must be locked all the way to its minimum. On this model camera, there is a little tab that must be pushed down by a boss on that aperture ring. Sometimes the boss, instead of pushing down the tab, will bump into it, but still allow the lens to seem to lock on. If the button is not pressed down, you'll get an error message that the lens is not recognized.

    Make sure that tab is pressed down freely all the way. If you force a lens on it can dent the tab. If this is your problem, you can usually solve it by very very slightly burnishing the sharp corner of the tab on the lens. Don't actually grind or sand anything off, just smooth the corner a tiny bit.

    An autofocus lens with no internal motor should register and meter on the camera, but will not autofocus.

    A lens with no electronics at all will not register at all on the camera. The camera will give a "lens not mounted" message in all modes except manual. It will work in manual mode, but will not operate the camera's meter.

    Just to keep terminology straight, "T-mount" is a universal, completely manual mount that allows a lens to be interchanged between cameras. It works only with manual or preset apertures, and is not seen much these days. You can use a T mount on your Nikon, but it will be 100 percent manual.

    You also must remember that the designation "auto" on most manual lenses does not refer to focus, but to the automatic aperture mechanism that allows you to view at full aperture.

    If this is a "g"type lens with no aperture ring, it should register with the camera with no problem, so in that case I would suspect a problem with the lens.
  • edited May 2015
    A further note. There are a number of lenses out there, which are 500mm, with a tele-extender to bring them to 1000 mm, which are indeed T-mount lenses. If this is indeed a T-mount lens it can be used only in manual mode. You will have to use preset aperture and manual focus, and either a handheld meter, or guesswork and histogram for exposure. Some of these are listed as being usable with a number of AF cameras, but they are, emphatically, not AF lenses.

    No T mount lens couples with a camera's meter. Higher end cameras can still do stop-down metering, but the D3xxx and D5xxx cannot do that either. You can guess exposure and then read the histogram for a shot you've made, and use that to fine tune your exposure for subsequent shots. This is not actually so hard to do if you get used to making good first guesses. My favorite 35 mm lens is an old Nikkor PC lens, which like a T mount has only preset aperture and no metering. You get used to it.

    For exposure, you start with the "sunny 16" rule and fine tune exposure after reading the histogram of one you've made. It becomes pretty easy after a while.
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