FD Breech Vs Bayonet... full aperture

Discussion in 'Canon FD' started by denny_rane, Feb 24, 2021.

  1. I tried to create the best title i could.
    Anyway........it seems like with the Breech-Lock lens, i can move the (one of, i guess there are two) aperture levers to a position that holds the lens "Wide Open". The lever will stay in that position
    So if i look through the lens, front to back, the lens will stay at its biggest setting.......2.8 2.0 1.8 or whatever it might be.

    But with the FDn, the bayonet style, i cannot do that. That same lever, on the lens, will not open the lens to its max aperture until it is mounted on a body.

    Is there a trick to doing that with the bayonet style, FDn lens?
    So i can hold the lens in my hand, and look through it at maximum aperture?
    thank you
     
  2. Many years ago, on a whim, I bought a metal, two-piece rear lens cap. One day, the rear of the cap popped out. Later, after I bought my first FDn lens, I found it useful for looking through the lens with the aperture wide open. IIRC, though, cutting out the back of a real Canon plastic cap won't work unless you modify it a bit. The mounting tabs on the metal cap I have is an exact copy of the mount on the camera bodies. I believe the real caps have tabs that restrict how much you can turn the cap...
     
  3. SCL

    SCL

    I cut out the rear of a plastic cap which I knew opened up the lens. It has worked for me for about 10 years.
     
  4. Canon used to make a little plastic thing that would do just what you're talking about. No idea what it was officially called. Probably best to make your own, as suggested above.
     
  5. Dustin McAmera

    Dustin McAmera Yorkshire, mostly on film.

    I have here in my hand an FD 85/1.8. Looking at the back with the rear cap off. If you were mounting the lens, you would be twisting the outer barrel anti-clockwise (looking from the back, remember), while the camera would hold the inner barrel still. Here, let's hold the outer still and twist the inner clockwise.
    If the red spot is at twelve o'clock, there's a chunky metal boss at about seven or eight o'clock, between the two levers. Hold the lens in your left hand, and place your thumb against that boss, ready to push on it, clockwise.
    Now in the channel round the edge, where the camera mount goes into, there are a couple of little metal pins; more like the ends of two metal strips; that project a tiny way out. One is between twelve and one o'clock, and one's at four or five. When you put the lens against the camera body, the pins are pushed in, so they're not in the way of the barrels rotating past each other. Get something to push with. I used a tiny screwdriver. I guess it would be ideal to arrange to push both pins at once. I managed to open my lens by pushing one, then the other pin, while applying pressure gently to the little boss. When it goes, the boss will move round to about ten o'clock, right next to the lens-release button, which will pop out. The lens should now be at full aperture, and the lower of the two levers stops it down.
     
  6. I will try that..... thank you :)
     
  7. There were 3 Canon made widgets for this purpose.

    1 the manual diaphragm adapter is a fidddly little bit of plastic you wedge against one of the levers on the back of the lens.

    2 macro hood which is, essentially, a rear cap with the back cut off. These are still easy to get on eBay and I use one.

    3 Stepping up a level of sophistication (& cost, which varies widely) there is the auto macro ring intended to be actuate reversed lenses or lenses on a manual extension tube with a double cable release but could be used to check lenses too.
     
  8. Dustin McAmera

    Dustin McAmera Yorkshire, mostly on film.

    I have a little plastic thing to hold the stop-down lever; it came with a Kiron reversing ring. You still have to release the mount yourself (and I suspect I may originally have learnt to do what I describe above from the Kiron instructions - don't know). The ring came without a hood, which sounds like a good thing to have.
     
  9. I think that the little widget is called a Manual Diaphragm Adapter. I have one but have no use for it. No idea how it came into my possession as all of my lenses are breach lock. If somebody really needs one, let me know.


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    Last edited: Mar 3, 2021
  10. I had the diaphragm adapter for reverse mounting my lens for macro. Now I use a piece of plastic to hold it when I use certain adapters to mount to my 5DSR.

    However, the easiest way I always used to open the aperture was to insert the rear cap, as if you are going to put it on, but rotate only about 1mm. This pushes all the release pins, so while holding the mount in its slightly rotated position gently slide the cap back out of the groove without rotating the mount back. It is tricky, but once you get the hang of it, it will work everytime.
     
  11. However, the easiest way I always used to open the aperture was to insert the rear cap, as if you are going to put it on, but rotate only about 1mm. This pushes all the release pins, so while holding the mount in its slightly rotated position gently slide the cap back out of the groove without rotating the mount back. It is tricky, but once you get the hang of it, it will work everytime.[/QUOTE]

    I was in a camera shop a few years back and looked at a 400mm BL lens. The clerk was surprised when I showed her this "trick".
     
  12. I will give that a shot as well.....never heard that before......Thanks
    I was in a camera shop a few years back and looked at a 400mm BL lens. The clerk was surprised when I showed her this "trick".[/QUOTE]
     

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