Discussion in 'Beginner Questions' started by robertbuck, Mar 7, 2018.

  1. I have an FD 100-300 zoom 1:5.6, my question is, because it only has 1 "f" number (5.6) does that mean it is a "prime" lens? I put my adapter to use it on my Xsi ,and turning the aperture ring has no affect on the irising in the lens. All of my other FDs you can see the aperture open and close when turning the ring. The ring has from 5.6 to 22 on it, the description on the barrel has only 5.6. When I take multiple photos with it of the same subject at the same settings (other than the "aperture) I see no difference in brightness or anything else...
    Thanks in advance RMBuck
  2. No, when people talk about a "prime lens" they typically mean a lens with a single focal length, i.e. a 50mm f/1.8. A 100-300 lens is a zoomlens, and hence not a prime.

    As for the problem you see:
    Maybe it's my fuzzy brain, but it is a bit confusing. Do you mean:
    1. Multiple photos, with different aperture but same ISO and same shutterspeed: image ends up identical
    2. Multiple photos, with different aperture and shutterspeed corrected (so stop lens to f/8, half the shutterspeed): image ends up identical

    I guess you mean (1), but just to be sure...
    If (1), it would mean indeed that the aperture has a problem. If the aperture does not close down while turning the ring, my guess would be a mechanical failure between aperture ring and the actual aperture blades (but I have no experience with Canon FD lenses, so I may be wrong).
    If (2), it would mean the lens works just fine.
    robertbuck likes this.
  3. As said, this is not a prime lens.

    As for not stopping down-it could be a couple of things.

    There are two levers on the back of an FD lens. WITH THE LENS MOUNTED ON A CAMERA(or "tricked" into such a position so that it will) the lever at the side will move into a position according to the aperture ring. The lever at the bottom will cause the lens to stop down to the set aperture when pushed over. With the lens off the camera, the side lever should be locked all the way to the top and the bottom lever won't do anything.

    If one of these two levers is bent or otherwise damaged, the lens won't stop down at all or will only stop down partially.
    robertbuck likes this.

  4. Exactly! Same ISO and Shutter speed, just adjusting the aperture by 1 F stop .....going from 5.6 to 22.....every pic is identical. So my used FD is probably not working correctly. I think I will take the adapter off and try the lens on an old AE program and see if the view finder is showing any difference.
    thanks again, RMBuck
  5. Just as an FYI, you will need to press the DOF preview lever to see the aperture opening and closing on your AE-1P. Normal operation on that camera is for the aperture to stay open until just before the shutter opens, and then open back up after the shutter closes.

    I've never owned an AE-1P(one of the few FD mount bodies I've not had) but I think the DOF preview lever works like it does on the A-1(my first "real" camera). If that's the case, it will lock ones you press it, and then when you're finished you push down on it to unlock it.
  6. Dustin McAmera

    Dustin McAmera Yorkshire, mostly on film.

    Is my Mir-1 37mm f/2.8 a prime prime?
  7. Dustin: Yes. There is another, I believe older, definition that a "prime lens" used to be the primary part of a combination lens. But mostly, by "prime", we mean a lens with a single focal length - one that's not a zoom lens. Not to be confused with a "fixed focus" lens - you can still focus most prime lenses.
  8. And if we really want to get picky, a zoom lens holds its focus over the focal length range.

    Back in the '80s when primes were king, one of the big lenses was the Vivitar Series 1 35-80mm 2.8 Varifocal. It was called a varifocal lens because the focus shifted dramatically as you changed focal lengths-but it was one of the first fast constant aperture lenses that covered the "normal" range. I have one in Canon FD mount, and though highly enough of it that the few times I was brave enough to do weddings(never again) it was a workhorse reception lens for me. That lens on a T90 loaded with Portra 400NC or even Superia 800 or 1600 and a 300TL flash made for a killer combo.

    I've played with the thought of picking up one of those lenses in Nikon mount, but they still bring surprisingly strong prices for a 3rd party manual focus lens. It's one of the few 3rd party lenses I'd be seen in public with gracing the front of my camera :)
  9. True. (I was nervous about writing that!) Colloquially, we tend to call any lens with a variable focal length a "zoom" (and we tend to call long lenses "telephoto" irrespective of whether they're technically telephoto, and Nikon is one of the few manufacturers who are pedantically correct about "macro" lenses...) - but in some circles (especially film making/TV) the distinction is important.

    Summary: Almost all photographic terminology gets abused a bit, and this isn't a new thing. Fortunately we normally know what we mean from context.

    On the other hand, I'm a stickler for the correct "f/2.8" aperture terminology that Dustin used, because people get very confused when they forget that it's a fraction and start trying to think in terms of aperture vs "smaller numbers"!
  10. James G. Dainis

    James G. Dainis Moderator

    "Auto" on a lens used to mean auto diaphragm. The aperture could be set to f/22 but the aperture would stay open until the shutter was pressed and then the aperture would automatically close down to the f/22 opening. It may be the adapter is not allowing the aperture pin to release to close down the aperture when the shutter is pressed.

    If you have a depth of field preview button use that to see if things darken down in the viewfinder when you press it and the lens is set to f/22. If you don't have a depth of field preview button, releasing the lens from the camera and turning it slightly should allow the diaphragm to close and darken things down in the viewfinder.
  11. That works for Nikon and I think several other bayonet mounts, but not for the FD mount. Turning the breech lock ring or the lens barrel(late "new FD mount" lenses really just have a breech lock ring the entire length of the barrel) actually locks the aperture in the open position. The lens WILL NOT stop down unless stop down lever on the back of the lens is pressed sideways.

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