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by evan-pak

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I'm trying to understand how adding the Dandelion chip to an old lens works in practice. I understand that the chip is programmed by the user with the focal length and max and min aperture. Am I right in thinking that operation is as follows?

  • The chipped lens is mounted on the camera.
  • The aperture ring is turned to minimum (but the aperture is held open by the camera aperture lever).
  • The shutter is pressed.
  • The camera calculates the required aperture.
  • The aperture lever moves down the required distance to give the desired aperture. (Contrast this with the early film cameras: on these the lever dropped all the way, allowing the lens to close down as far as the aperture setting.)

This requires that the aperture mechanism on the lens behaves in a similar way from lens to lens.

If this is so, then how accurate would it be with, for example, a Tamron lens on an Adaptall 2 - Nikon adaptor?

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up vote 1 down vote accepted

The Adaptall 2 mount lenses do have a linear aperture actuator, otherwise they couldn't be used in Program or shutter priority mode on cameras that offered the feature(s). And they certainly did work in "P" mode on the Minolta X700. (Except for the 500mm/8, obviously.) The most complicated part of the mount adapter was the lever mechanism that went between the camera's aperture lever and the lens's aperture actuator; on some long-flange-distance mounts, there wasn't a whole lot of room inside the adapter to correct the ratio, so it would require a multistage approach.

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What's obvious about why the 500mm/8 wouldn't work? – Transistor Mar 25 '14 at 12:27
@Transistor - It's not that it "won't work"; it's a fixed-aperture reflex (mirror/catadioptric) lens. – user2719 Mar 25 '14 at 12:36

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