Nikon n75 with AF 1.8 lens.

Hello,

I am new to this forum so please, be gentle :)

I bought a nikon n75 6 months ago and I am very pleased with it. About two weeks ago, I bought this lens off eBay:

http://cgi.ebay.com/ws/eBayISAPI.dll...ME:B:EOAB:US:6

I received it today and tried it but here is a thing:

in order to have it to work, I have to set the aperture to f22 and then turn the camera on. (this is normal, according to Nikon.) But if I want to change the paerture, I can not use the aperture ring, otherwise it blocks the shutter. I have to use the control dial that allows me to open to 1.8. But here is my surprise: the "curtain" inside the lens stays closed down to f22, even when the control displays indicates the aperture is a 1.8. Is the lens not working? The AF works well, so I guess the lens is compatible, but I do not see how I can have an aperture of 1.8 if the "curtain" is closed at f22. How does that magic works???

Thank you very much. I am very worried about this.

Matthieu

Hi,

I just got back from a trip round southern France so I missed this post.

I have the F75 and the 50mm f1.8 shown in your EBAY entry. You have to set the lens to f22 for it to work with any modern Nikon body. If you want to specifically set the aperture then you set your camera to A-priority and use the knurled wheel on the back of the camera to set the desired aperture. (this is also standard Nikon user interface).

It sounds like you're saying that the diaphragm (curtain) on the lens is closing down to f22 at all times. I've tried to make mine do that and so far I haven't succeeded. Is your camera set to A-priority mode and your lens set to f22? Puzzled.

Charles

Sounds strange to me too. On AF Nikons, you do put the lens at f22 and lock it (flip up the tab next to the f1.8 stop). Once you get the hang of changing aperture from the body you'll probably work it quicker, I prefer it now.

Are you talking about the cirular aperture blades that are inside the lens? If they're closed down to f22 when the lens is on the camera, then the viewfinder would be so dark you'd have a hard time seeing anything through it. The AF wouldn't work either - AF systems need lenses at least f5.6 to work reliably and by stopping down to f22 like that you effectively have an f22 lens.

Two things that might cause that - is the lens fully attached to the body (as in put on and twisted to the right until it clicks)? Are you hitting the depth of field button (admit I don't know if the N75 has one)?

The lens should be open to f1.8 at almost all times. When you stop down to - for example - f8, this sequence of events should happen: Press shutter release. Lens aperture closes to f8 and mirror goes up. Shutter opens and closes. Lens aperture opens back up to maximum and mirror drops back down. Film advances. (There are other things happening too, but to keep it simple...). If this isn't happening, then there's a problem somewhere.

[QUOTE=But here is my surprise: the "curtain" inside the lens stays closed down to f22, even when the control displays indicates the aperture is a 1.8. Is the lens not working? The AF works well, so I guess the lens is compatible, but I do not see how I can have an aperture of 1.8 if the "curtain" is closed at f22. How does that magic works???[/QUOTE]


Let's pause for a moment here. What makes you think the lens is stopped down to f/22 when the display says 1.8? The only time the lens should be at anything other than wide open (f/1.8) is during the actual exposure or if the lens is removed from the body.

The way the mechanics work is like this:

1) With the lens off the camera, the diaphragm will stop down to whatever the lens's aperture ring is set to; f/22 in this case.

2) There is a lever that sticks out in back of the lens mount that works the diaphragm -- if you move that lever with your finger, the diaphragm will open and when you release the lever, the diaphragm closes again.

3) When you mount the lens on the camera, the lever is automatically moved so that the diaphragm opens all the way --that's why the view through the viewfinder is bright and easy to see -- and the diaphragm stays wide open no matter what you set with the aperture dial on the body.

4) So let's say you choose an aperture of f/8. When you take a picture, the diaphragm lever is moved just the right amount to close the diaphragm to f/8. The important part here is that the diaphragm mechanically can't close down past whatever the lens's aperture ring is set to -- that's why we set it to f/22.

5) When the exposure is complete, the diaphragm reopens to its maximum aperture.

Hope this helps.


Regards
Dennis

Quote:

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Originally Posted by Franglais

It sounds like you're saying that the diaphragm (curtain) on the lens is closing down to f22 at all times. I've tried to make mine do that and so far I haven't succeeded. Is your camera set to A-priority mode and your lens set to f22? Puzzled.

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I found the depth-of-field preview button (on the right side, next to the lens mount), which stops the lens down to the aperture selected on the body - as long as you keep it pressed. But that's not the same as having the lens closed down to f22 all the time. As someone else said, the only reason the lens should stop down to f22 all the time is if its not properly mounted, but then the autofocus wouldn't work.

Still puzzled.

since this is a modern 50 f1.8 AF lens.....

change the wording from "lever" to "electrical contacts" and the ABOVE statements by my fellow NJ-ite are ABSOLUTELY 100% ACCURATE ;)

Quote:

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Originally Posted by paulnj

since this is a modern 50 f1.8 AF lens.....

change the wording from "lever" to "electrical contacts" and the ABOVE statements by my fellow NJ-ite are ABSOLUTELY 100% ACCURATE ;)

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Paul - I gotta call you on this one. I have a 50 f1.4 shown here but it should work the same way - all mine have levers. First shot is with the lens at f16 (closed all the way, no f22 on this lens) but with the lever flipped to open the aperture up. That's what should be happening when it's on the camera. Disclaimer: Don't try this at home. Professional driver on a closed course. Of all the shots I've taken, well - uh - these are certainly the most recent :rolleyes: !

Matt - Second shot is the front of the lens at f16 - see how small the aperture is? Last one is wide open at f1.4. Your range of f1.8 to f22 should appear about identical.

Sorry for the really lame pictures but I hope they explain what I'm saying. Does this help?

So I was mistaken :)

Since my switch to CANON, I have RARELY used my NIKON GEAR...... but imagine my delite when EVERY NIKON lens I own has that same lever :D