Nikon AF-S 28–70mm 2.8D lens: Aperture Coupling
Transcript
Hello everyone. [This is a] quick little video.
Common issues people have with this lens
I see on the internet constantly people have trouble with this lens. This is the AF 28-70mm. The big problem is getting the diaphragm back in. Everybody can pull it out, but nobody can get the diaphragm back in. Let’s go ahead and take this apart. I’ll show you how to get these things in.
I’ve been doing these for many, many years and, even for me, every once in a while, they just can be a struggle.
Remove the mount ring
We’ll just go ahead and take this rear ring off, the mount ring. That’s this one here. [It has] three flat head screws. This is a junk lens, so I’m not too worried about this lens.
Okay, so that guy comes off. Okay, this was loose because I took out the one screw; it should have two but only had one on this lens.
We’re going to go ahead and take these [screws] out. These are not tight because it’s been apart. Someone tried to have a go at fixing it, but this [lens] is just too far gone for repair. This is my junker lens.
Take out all the long screws
Okay so as I’m taking apart this, if you look really carefully, that’s a threaded screw and they’re different from the other screws. The other screws look like that — nice long ones. The difference — if you take this one out and you take the mount off, then you’re just adding to your workload so put this one [threaded screw] back in. Keep it in. I always forget if it’s this one or this one, so that one — keep in. You don’t need to take it out.
This long one here, you do, so all the long screws need to come out. There should be four of them. You want to take out every screw on a Nikon mount. Go ahead and pull that up.
Remove the coupler to access the diaphragm
There’s your coupler — that drives your ASA. Your camera will kick it here and that drives your aperture.
Alright so the big problem with this guy is the diaphragm coupling. Let’s see if I can even get a light in there. It’s way down inside the lens here, way down there.
How the diaphragm should work
This is what your diaphragm looks like. This is from another lens, a junker. So, what you have is you have are these two points right here. When you drop this lever down in, it needs to hit here, push that open, and then drop in. So that’s how it should look when you’re done and it’s working correctly, I hope you can see that.
Unfortunately, many people miss it. They drop it here, they drop it here, or the worst is they drop it here and keep pushing down until this system bends or this bends. This is just like a little lip. You can set that on, open it up and then it drops back in.
It’s kind of a funky little system. There are a few Nikon lenses that use it and then drives the diaphragm open and closed. If you miss it, nothing’s going to happen, you might get some movement, but it’s not right. You see it doesn’t stop down all the way and if you hit it way over here, you’ll open and once again you don’t get proper diaphragm operation.
So, it needs to go down the middle — boom — all the way closed or all the way open. That’s the best way I can explain how these things work. Really what you’re doing is — if you use fingers [as a representation of the action] — what you’re doing is you’re opening and it just has to drop in.
How to put the diaphragm back in
To get this thing back together, just put the spacer on back focus — don’t forget your back focus washers — they all need to go on unless you have a way of adjusting it. Then, unfortunately, you just have to look down this lens. Even I have a tough time seeing it.
And I’m hoping — I’m actually doing it by feel right now, because I really can’t see it. Nope, I can’t see it. I need more light. There we are; I can see it now.
Even with all my experience, I have trouble sometimes
It can be a real pain, so I understand people having trouble with this lens. I’ve been doing this for years. (There, I got it!) That’s probably 30 years of experience right there, so if you all have problems doing this, understand [how experience makes a difference.] Hopefully this makes it a little bit easier on you.
Use the screw for alignment
Okay, black screw into the front. This becomes an alignment — I guess you would call it a key — so you key in on that screw. Put it on; it’s like the white dot — so white dot, black screw — and the rest ones are just long ones. They don’t matter, they’re just chrome ones.
And then, we get it back together and I just wanted to do this [the video] really quick.I hope [the video] is not too long. Looks like we’re running around five minutes on it.
Be sure to use conical head screws in the right spots
Then you just put the rest of it back together. When you’re looking for screws please — and I see this; I don’t know why — but that’s a conical head screw. I wish, I don’t know if you can see it, that’s conical head screw, that’s going to go here [the side]. You don’t want screws sticking out in here.
People put the wrong screws in here and it messes up the holes, messes up the backing plate. There’s the backing plate right there. If you drill the wrong screw in, the screws stick out and you can’t mount your lens on. I don’t know how many times I see that. I’ve seen that quite a bit. “I can’t figure out why it doesn’t mount.” Well, you put the screws in wrong; you shouldn’t have been playing with it.
Put the mount ring back on
Alright, and then the mount ring goes in. There’s only one way it really goes in, and then these [screws] have heads on them. So that the heads on these screws go into the recess. When it all goes on, they’re all going to be flush; nothing’s going to be sticking out.
Make sure there’s a stop screw
There’s only one screw that needs to stick out and that’s that one right there. I don’t know if you can tell on it but that’s sticking out. That’s your stop screw. If that stop screw is missing, you’re going to damage your camera every time.
And that’s pretty much it. I’m going to end here. This is just a quick little video.
Well, good luck with it. If you have any questions, just ask. Take care, bye.