Not Joy My new not working lenses have arrived

Ok, i received these two chinar lenses.

On one, the apeture diaphram opens and closes and stops down all the way.

On the other, the 135mm one, the diaphram does not move at all, not even
partially.


here is the lens, looking thru the back, at f2.8
http://i2.photobucket.com/albums/y13/Nygdan/Picture001.jpg

and here it is at f22
http://i2.photobucket.com/albums/y13/Nygdan/Picture002.jpg


Now I don't know if its that longer lenses act differently or what, but I'm
thinking I just got burnt on an ebay deal. Can anyone confirm, to be sure,
what might be rather obvious, that this lens does not work?

 

You haven't named your camera mount, but most open-aperture-metering
lenses have a lever that needs to be moved, to stop the lens down. I
guess it's vaguely possible you have bought one very old manual style
lens that is not open-aperture, and one that is. There may also be an
'auto/manual' switch..

Is there some reason why you can't just stick them on your camera, open
the back, and fire away? Most cameras will allow this in manual mode..
You will soon see what is happening, and whether it stops down when it
needs to.

If you can't work this out, take it to a camera store - I'm sure they
will enlighten you for free.. I'm sorry if i am stating the obvious,
but you supplied very little info, and Chinar is not exactly a
'name-brand'....

Longer lenses don't work differently unless they are mirror lenses, and
this is not one of those..

 

Did you hit the stop down pin/lever ?

 

K-mount. I have a k1000. The Rear lens caps have 'pK' so I'm thinking
that that means that its one that can work in program mode

I have a roll of unexposed film in my camera right now and am wary
about taking one lens off and replacing it. Perhaps thats kind of
silly, but I don't like the idea of wasting even a few exposures or
loosing the ones that I've already taken. I suppose I could just do it
in the dark tho.

I hadn't thought that there was much of a possibility of it /not/
moving while it wasn't attached to the camera. Perhaps since there is I
should do like you suggest.

I did try putting it to f22, and then tapping the lever in the back.
There's little resistancebut it does spring back to its original
position. But throughout there is no movement in the lens.


snip

 

these are k mount lenses. they read 'pk' on the cap.
Alan Browne wrote:
snip

Yeah, I was reluctant to do this at first but someone in another forum
suggested it. No reaction, but the lever (this is called the coupler
no?) does spring back to its original position. No movement inside the
lens.

I might just have to mount it on the camera and see what happens. I
didn't want to do that because I have unexposed film in there. I might
have to go out and use it. This might not be too bad of a thing!

 

Shoot a couple frames with it set to wide open and closed down. Film's
cheap. But from what you describe it appears the aperture stop down
dows not work

 

Alan Browne <> on 16 Mar 2005 posted

Well, I attached the lens to my camera, and now I am even more confused.

Like i said, i can't see the diaphragm opening and closing down to the
middle of the lens, or really any movement at all.

But with it attached to the k1000, if i turn the apeture ring, i get
results in the ttl metering. But this /can't/ happen if the apeture
diaphragm isn't operating no? I mean, the k1000 body has no idea whats
going on in terms of apeture or anything, it simply meters based on whats
comeing thru the lens.

I have no idea what is up now. I'd like to not have to waste a whole roll
of film trying to see if there is a change in dof that would be caused by
a moving apeture.

 

Yes. - Your camera should overexpose the picture, because it thinks the lens
was held wide open when it metered the light. Then, just before it takes the
picture, it assumes that it stopped the lens down to where your aperture
ring says it is, and that was where it calculated the exposure time. But,
since the little cam that is supposed to hole the lens wide open isn't
working, it metered the light at the stopped down position instead of the
wide open position, so its calculation is off by however many stops the lens
is stuck at below its wide open position. The only pictures you take that
will be correct, are those taken with the lens wide open anyway. In this
case, the cameras calculation will be accurate.

 

If you have tried to close the diaphragm by moving the lever on the back of
the lens and the diaphragm will not close (assuming you have the f-stop set
to F8 or f16 ) then you have a problem in with the diaphragm. On the K1000
there is a lever next to the lens mount that is moved when you turn the
f-stop ring on the lens otherwise the camera's meter would not know what
f-stop the lens was set to.
I think your problem is two fold. 1. You are not very familiar with your
camera and or #2, the lenses you purchased are defective.

 

I mean, the k1000 body has no idea whats

I think you wil find that the K1000 uses 'open-aperture' metering. As
you change the aperture on the lens, it does NOT stop down, but the
lever at the back of the lens `tells` the camera what aperture you have
stopped down to. When you take the picture, the lever is moved so the
aperture briefly closes down to whatever you have set, then it springs
back to fully open again. This allows you to always view the scene
with the lens wide open, rather than have a dim, stopped down view.

That is why most (but not all) K-Mount lenses will NOT close down when
you adjust the aperture setting, whether on or off the camera. Until
that lever at the back of the lens is moved, they should stay wide
open. There are some fully manual K-Mount lenses but they are not
common. Lots more info here:

http://www.bdimitrov.de/kmp/technology/K-mount/K.html

 

They won't stop down on the camera until the photo is taken (or DOF preview
is activated), but if the lens is off the camera it will stop down to
whatever aperture is selected. With the lens off camera and set to the
smallest aperture (eg F16, F22 etc), the lens should clearly appear to be
stopped down. moving the spring loaded lever on the back of the lens should
open the aperture. From the OP's description, it sounds like the aperture
mechanism in his lens is broken.

 

R.Schenck wrote:

No. When you adjust the aperture, the aperture _setting_ is read by the
camera as well as the max aperture. The aperture remains open while you
make adjustments. The meter reading is 'offset' according to the
aperture selection. The aperture is only actually closed when you
depress the shutter.

(Note there are some camera/lens systems that have stopped down metering
where the lens _does_ stop down the aperture for meter readings... but
yours is not one of them).

You just need to shoot a couple frames and get back to regular shooting
with other lenses.

Film is cheap.

Cheers,
Alan.

 

:
: wrote:
: > You haven't named your camera mount,
: K-mount. I have a k1000. The Rear lens caps have 'pK' so I'm thinking
: that that means that its one that can work in program mode
:
No, that stands for Pentax K. If it could work in program mode, it would say
PKA.

Paul

 

Justin, you are quite right, a normal K-Mount, full-aperture-metering
lens *should* stop down while off the camera. Moving the lever while
it is off camera *opens* the aperture, and I thought it was the other
way around. Just goes to show how long my Pentax lenses have sat
gathering dust since I moved to digital.. (O;