December 21, 2014, 11:30:51 PM

Author Topic: a 70-200mm not focussing.  (Read 577 times)

gjones5252

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a 70-200mm not focussing.
« on: May 19, 2014, 02:41:24 PM »
I went to yellowstone this past week and half way through the trip my 70-200mm 2.8 ii would stop focussing on the wide end. Tried it on two bodies same thing. I noticed after inspection the back screws on the lenses are coming out. I screwed them back in and within an day they were coming back out. Also if I focus it while zoomed at 200mm and pull focus back to 70 it will go in and out of focus. I don't remember it ever doing this. Can anyone else check their 70-200mm?
I have a warranty but if it gets fixed instead of replaced I just would like to know what to check and what the potential problems could be?
Thank you for anyone who has any ideas.

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a 70-200mm not focussing.
« on: May 19, 2014, 02:41:24 PM »

dgatwood

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Re: a 70-200mm not focussing.
« Reply #1 on: May 20, 2014, 11:49:01 PM »
I went to yellowstone this past week and half way through the trip my 70-200mm 2.8 ii would stop focussing on the wide end. Tried it on two bodies same thing. I noticed after inspection the back screws on the lenses are coming out. I screwed them back in and within an day they were coming back out. Also if I focus it while zoomed at 200mm and pull focus back to 70 it will go in and out of focus. I don't remember it ever doing this. Can anyone else check their 70-200mm?
I have a warranty but if it gets fixed instead of replaced I just would like to know what to check and what the potential problems could be?
Thank you for anyone who has any ideas.

If those screws are holding the lens mount in place, then their absence could change the focusing behavior by changing the distance from the back element to the sensor.  If the focusing problem goes away when the screws are tight, then you might try putting a tiny bit of clear nail polish on the screws and then screwing them back in.  That should keep them from working their way out, and it will save you a trip to the repair shop, where they'll basically do exactly that, only with slightly more expensive blue paint.  :D

privatebydesign

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Re: a 70-200mm not focussing.
« Reply #2 on: May 21, 2014, 12:03:31 AM »
Absolutely don't worry about it, I had the same thing happen to my MkI years ago, mine was so bad it undid into the lens lock detent and it took an engineer to separate the two. Just use a tiny bit of lock tight to keep them tight, there won't be any damage if you haven't dropped or knocked it, the misfocus will sort itself out once they are all tight. The screws are not Phillips heads, they are JIC heads, normally Phillips won't tighten them enough, if you don't have the right screws any camera shop will tighten them up for a couple of dollars.

gjones5252

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Re: a 70-200mm not focussing.
« Reply #3 on: May 21, 2014, 12:32:56 AM »
ok awesome, ill try screwing them back in fully and see if the focus issues go away. Hopefully its something small like that! thank you for your responses, ill update you when its fixed

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Re: a 70-200mm not focussing.
« Reply #4 on: May 22, 2014, 12:54:59 AM »
When you tighten the screws, be sure to use the right screwdriver, those heads are not Phillips, and can be messed up with a Phillips.  You can't tighten it properly with a Phillips, since the bit slips.
 
Get a JIS screwdricer (Japan Industrial Standard).  Then, you can torque it down properly, and a little locktite works great.  Don't use nail polish.

dgatwood

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Re: a 70-200mm not focussing.
« Reply #5 on: May 22, 2014, 02:47:11 AM »
When you tighten the screws, be sure to use the right screwdriver, those heads are not Phillips, and can be messed up with a Phillips.  You can't tighten it properly with a Phillips, since the bit slips.
 
Get a JIS screwdricer (Japan Industrial Standard).  Then, you can torque it down properly, and a little locktite works great.  Don't use nail polish.

*shrugs*  Nail polish works better for people who aren't used to applying the stuff, because it starts out thicker than Loctite, and therefore is less likely to drip where it shouldn't.  Like on your lens glass.

Valvebounce

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Re: a 70-200mm not focussing.
« Reply #6 on: May 29, 2014, 04:20:03 AM »
Hi Folks.
From someone who found out the hard way (a long time ago on an old radio) that Philips and Pozidrive are not the only cross head screw standards get a set of JIC screwdrivers!
Only thought on nail polish vs loctite, nail polish is a cosmetic treatment, loctite is an engineering adhesive made for this type of application, either remove the screw completely apply by touching the screw thread to a drip of loctite on a surface such as a bit of masking tape, or dip a cocktail stick in to the same drip and apply to loosened screw.
I always prefer to apply to the thread not under or on the head, but that may be sufficient for this application.
If you are going to remove the screw completely do it with the lens stood on its end so that if the mount has shims under the screws they won't slide out!

Cheers Graham.


When you tighten the screws, be sure to use the right screwdriver, those heads are not Phillips, and can be messed up with a Phillips.  You can't tighten it properly with a Phillips, since the bit slips.
 
Get a JIS screwdricer (Japan Industrial Standard).  Then, you can torque it down properly, and a little locktite works great.  Don't use nail polish.

*shrugs*  Nail polish works better for people who aren't used to applying the stuff, because it starts out thicker than Loctite, and therefore is less likely to drip where it shouldn't.  Like on your lens glass.
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Re: a 70-200mm not focussing.
« Reply #6 on: May 29, 2014, 04:20:03 AM »