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did I get the wrong adapter?
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PostPosted: Sat Mar 27, 2010 2:26 am    Post subject: did I get the wrong adapter? Reply with quote

Ok, so I finally receive my m42 > eos adapter from "big is" on ebay. The mount is very nice, great quality, but there is some clearance issues that I don't understand.

The aperture "peg" on the back of the mount, by the back element, hits the mount. So, when screwed in all the way, the aperture ring doesn't spin freely.

did I just get a bad sample, or am I doing something wrong? I have extension tubes that fit perfectly, so don't think it's a lens issue.

hopefully this makes sense.

here is a pic of the problem aperture "peg"

PostPosted: Sat Mar 27, 2010 2:42 am    Post subject: Reply with quote

Do you have a picture of the adapter on the lense?

PostPosted: Sat Mar 27, 2010 7:10 am    Post subject: Reply with quote

You simply ordered the wrong adaptor for this specific M42 Lens..
there is nothing wrong with BIG IS Adaptors...

There are two version M42 to EOS. One is a simple adaptor, without a inner ring on the end of the thread. The other one has the inner ring to push down the aperure pin of the old M42 lenses without an A-M switch.

IMHO you have got the one with the inner ring on the end of the thread.
The Apterure lever shown in your image was blocked by the inner ring if you screw in the lens.. thats all.

Either buy one without the inner ring plate, or unscrew the lens mount and
get rid of the lever.

If you do so, also remove the small needle pin.. after reassembling everything should work fine for you.


PostPosted: Sun Mar 28, 2010 5:26 am    Post subject: Reply with quote

what would keep the aperature pin pushed in if there wasn't a back?

I was just thinking of filing down the aperature peg.

but you are saying if you have the peg, you need a mount without a back?

I just don't want to wait another 10 days for the correct mount. doh, wish I would have known.

PostPosted: Sun Mar 28, 2010 6:09 am    Post subject: Reply with quote

Switch to manual mode to use change the aperture without pushing the pin in Smile If the switch won't budge to the manual position, you'll need to push the tiny button in on the mount of the lens (with a pin), which will allow you to do so Smile

PostPosted: Sun Mar 28, 2010 8:32 am    Post subject: Reply with quote

There are two different kinds of adaptors..

Your problem is not only the small needle pin (marked left hand).. its the lever, red marked right side of the image... the aperture slider..

Here are the two kinds of M42 Adaptors.. have a look at the different Diameter ... the black one has a smaller diameter because of the inner Ring, which normally press down the aperture closing needle - pin.

What you see (the left mark) on your first picture is not a pin like you know it from many M42 lenses.

Have a look and compair your lens and the shown "normal" M42 Lens, whats in what position... correct, look at top of the M42 threadmount!
There is not the M42 pressdown pin on your lens.. thats your problem, there is a aperture slider ! File them down or open the Mount and dismantle this slider.. thats the part which blocks!

And this shows the problem.. (taken from another image)

As you can see, the inner ring blocks the aperture lever shown in picture 1.

Either you unmount this aperture lever which blocks after screw in the lens or file down the inner ring of the Adaptor.

Another detail in your picture of your lens is also important if you do use an adaptor with the inner ring..

On your picture is a small "block" on top of the M42 Thread-Mount.. this propably could cause a problem for reaching infinity on the lens.
So the best way IMHO would be to look for an adaptor without the inner ring/plate (which should press down the needle aperture pin)... !!


PostPosted: Sun Mar 28, 2010 9:10 pm    Post subject: Reply with quote

thanks for the replies and images. The lens I showed isn't my lens, just an example of what my lens is designed like.

looks like I'll be grabbing another adapter.

thanks again!