Preview (new toy)-- Praktica B Auto Focus lens

Discussion in 'Modern Film Cameras' started by JDMvW, May 4, 2021.

  1. Not yet a report, but as soon as I get some new batteries (AAA for the lens AF) and 6-volt for the Praktica B20) I'll be back. REcent mention of it on this site, reminded me that I had not yet acquired this last piece in my DDR collection (heaven help me I do collect them).

    The camera I plan to use is essentially the ultimate Praktica from the workers' and peasants' state, the Deutsche Demokratische Republik. The camera that followed it, the BX20s, was the last gasp of Pentacon production and I think most were sold after the end of the Republik.
    It has 'electronic' controlled automatic exposure (the 3 brass pins on the lens and body). This development was one of VEB Pentacon's last contributions to the camera world

    The 55-200mm AF lens may have been designed in the DDR, but it was manufactured by Sigma in Japan (LINK). Here is the lens on the Praktica BX20.
    01 Praktica-BX20-w55-200-AF-143.jpg

    The AF is activated (we shall see if it works) by pressing the shutter release part way. That also locks focus.

    When I can get all the components together and it stops raining, I'll be back.
    John Farrell likes this.
  2. Interesting. I always thought that the three contacts were purely for meter coupling. I think a variable resistor in the lens, coupled to the aperture ring, transmitted its value to the body to "tell" the metering what aperture the lens was set to. Similar I think to the earlier Pentacon Electric screw fit lenses, which also had three contacts. If half pressing the shutter initiates AF, via the body-lens contacts, it seems that Pentacon had allowed for additional future developments like AF
  3. Yes because of the less precise positioning in a screw mount, I guess, the contacts on the L-series electronic were wider: Praktica-EE2-body-and-lens-arrows.jpg
    Praktica 42x1.0 mount electronic connections - on the Praktica EE2 of 1977 (LINK)
    The BX20 and other B-mount Prakticas continued the excellent series of vertical metal shutters (like the Copal, maybe even better) of the L series.
    Praktica BX20 shutter 49e.jpg
    John Farrell likes this.
  4. Follow-up

    I got some batteries, but the AF on the lens does not seem to work completely.

    When, if ever, I solve the problem, I'll be back.
  5. Does the AF activate from the camera JD? Or is there a switch on the lens?

    I had a similar Nikon fit AF-in-lens Tamron 70-210mm zoom, which stopped functioning after a couple of years. I'm pretty sure I still have all the parts stashed away somewhere, after an abandoned repair attempt. Pesky printed ribbon connectors!:mad:

    The lens was optically pretty good - at least with film - but the AF was slow and a bit unreliable.

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