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03-17-2011, 11:42 AM   #1
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Sigma Pantel 300mm f5.6 m42 with issue

Hi

Recently acquired this as part of a package. Unfortunately the aperture isn't working. has anyone ever worked on one that can give me a few tips (it shoots wide open just fine)

03-18-2011, 07:02 AM   #2
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How is the aperture not working? Does the aperture ring spin without effect or clicks? Is the ring jammed? Is an iris blade jammed?

If the ring spins clicklessly, then a wee bearing has gone lost and needs replacement.
If the ring is jammed, the lens obviously needs disassembly.
If an iris blade is jammed, you *might* be able to remove the lens base and put it right. I have done that with a couple lenses.

So, what's up?
03-18-2011, 07:12 AM   #3
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Ring turns and clicks (very lightly) at stops but blades remain open (it may well be the ball bearing you mention). moving the pin on the bottom does nothing to shut down the iris

I've tried a couple of shots with it wide open and it's a pretty soft lens in any case (not something i will put a huge amount of effort into) wide open or close to is probably how i would end up using it so for now it will be a fixed 5.6 lens

I figured it would be you or DucDao who had an answer. it seems to be a hard lens to find info on. I really grabbed the set for the 1.4 tak with a nice shade with it. Also got a Spottie in VG shape (better than my HV) and a 135 f3.5 that is a little stiff in the focus, but otherwise works well. for $100 i have no complaints, and there was a guy pursuing just the 300 for $60 so i can always sell it on, But i have no 300 so for now
03-18-2011, 08:13 AM   #4
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Oh, I have no experience with that lens, just with a few faulty apertures. But here's an idea to sharpen it up a little: make a Waterhouse-stop disc from black plastic, to fit inside the lens throat just ahead of the mount. I use something similar with some bellows-mount stuff. It's more of a 'choke' than a 'stop' but it seems to make a difference. Hay, it's cheap and easy!

03-18-2011, 08:19 AM   #5
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QuoteOriginally posted by RioRico Quote
Oh, I have no experience with that lens, just with a few faulty apertures. But here's an idea to sharpen it up a little: make a Waterhouse-stop disc from black plastic, to fit inside the lens throat just ahead of the mount. I use something similar with some bellows-mount stuff. It's more of a 'choke' than a 'stop' but it seems to make a difference. Hay, it's cheap and easy!
you may have no experience with the particular lens but you are known for mastering conversions etc
the stop disc is a neat idea, i'll have to look closer at the lens this weekend
can't hurt anyway
and some judicious contrast/curves in LR can work wonders
I shoe a couple of throwaways testing it (tree branches from a couple of hundred yards against a bright blue sky) and it doesn't seem to suffer any serious fringing issues so it's not all bad
need to haul it to the beach tomorrow and shoot some ducks/geese/swans and see what it can do
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