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02-23-2014, 04:07 AM   #1
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Sigma 70-210mm F4-5.6 UC disassembling?

Hi,

I have Sigma 70-210mm F4-5.6 UC which suffers from one problem - unable to have a good focus when one tries to focus to infinity. I was wondering does anyone has some advice (since I bought it very cheap) how to disassemble it? As I can see there are couple of screws where the mount is, but how can I get to the focus part?

Kind regards and thank you.

02-23-2014, 04:26 AM   #2
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Does it not reach infinity or does it focus past infinity? Focusing past infinity is a good thing because the lens barrel expands and contracts with temperature.

Do you have a picture of that lens? I've had a manual focus Sigma 70-210 apart in a failed attempt to clean some fungus. From what I remember under the rubber grip is some tape. I believe the process to set infinity on one like this is to set the lens to the infinity mark, then remove the tape, turn the front half until you achieve infinity and then replace the tape.
02-23-2014, 05:00 AM   #3
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QuoteOriginally posted by elliott Quote
Does it not reach infinity or does it focus past infinity? Focusing past infinity is a good thing because the lens barrel expands and contracts with temperature.

Do you have a picture of that lens? I've had a manual focus Sigma 70-210 apart in a failed attempt to clean some fungus. From what I remember under the rubber grip is some tape. I believe the process to set infinity on one like this is to set the lens to the infinity mark, then remove the tape, turn the front half until you achieve infinity and then replace the tape.
If you're asking me does the focus part reach that little signe "∞" then the answer is: yes it does. The second part of the first question I don't understand; what do you mean by "focus past infinity"?
Pictures of that lens.
Edit: Adding additional info about this problem:

When one tries to focus an object which is more than 20m (example, tryed to focus a ferry which is around 150m from camera), it seems (and feels) like the focus ring needs one or two millimetres to have a clear image. I compareed few pictures with smc 135mm f2.5 and it's obvious that one or two mm in focus ring is, somehow, "missing"(?).
When I try to use auto focus and focus to infinity, focus indicator wouldn't stop blinking which means that camera can't focus object that are over 20m (to infinity). Nevertheless, i did some shoots from 3-20m and there everything is ok;
I have done some tests and unable to focus to infinity is the problem from 70-210mm and if one using autofocus, then the focus indicator is blinking all the time.

Last edited by malenisjaj; 02-23-2014 at 05:40 AM.
02-23-2014, 11:34 AM   #4
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I don't know anything about the auto focus version unfortunately. There usually is something hidden under the rubber grip though.

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