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Old October 25th, 2011, 01:34 AM   #1
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Back focus slipping

I just wanted to know if there are other HM 700 users that have noticed that they need to adjust their back focus often. I have the Fuji 17x lens and I have to adjust it almost every time I take it out of my bag lately and I crank the screw tight. I have talked with another HM 700 user in my area and he is experiencing the same problem. Any one seeing the same thing or have any suggestions. Thanks.
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Old October 25th, 2011, 03:33 AM   #2
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Re: Back focus slipping

it should be something you do for every professional shoot, variances in temperature cause metal to expand an contract, this causes the back focus to move slightly. Nothing major.
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Old October 25th, 2011, 05:39 AM   #3
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Re: Back focus slipping

Yes Calvin,
I am having the same problem with my Canon lens. I always make sure that screw is tight, but it seems like I have to do it every time I get it out of the bag.
Not much help, I know, but at least you know you are certainly not alone!
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Old October 25th, 2011, 08:44 AM   #4
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Re: Back focus slipping

I've had this problem on all 1/3" bayonet lenses I've ever used on the JVC ProHD cameras. I would expect to check back focus regularly anyway but you really do have to be vigilant on these cameras. The new(er) bundled Canon lens seems to be the worst culprit but the Fujis (new and old) seem to be pretty dodgy in this regard as well.
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Old October 25th, 2011, 06:23 PM   #5
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Re: Back focus slipping

Had an issue with one of my HD200s with stock 16x5.5 last week as well. Seem to be slipping more than any other lenses I have used.
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Old October 26th, 2011, 10:33 AM   #6
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Re: Back focus slipping

We have had the same issue with the Canon 14x. I spent considerable time trouble shooting the issue and found an interesting problem.
The Macro ring is connected to the back focus ring. When you set the back focus the Macro ring turns with it. Makes sense. The problem is that when everything is locked down (thumbscrew tight, macro ring locked in place) there is a small amount of play in the macro ring. Enough play to affect back focus. So, if the back focus is perfect and you twist the macro ring for some reason it can make the back focus go out of whack.
Just a little bit and difficult to catch in the viewfinder but very soft on wide shots when you see it on a monitor.
I don't know if this is the same issue others have, but I sent the lens off to Canon for service and replacement of the Macro ring. Due back this week. It will be interesting to see if the problem is fixed!
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Old October 30th, 2011, 10:26 PM   #7
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Re: Back focus slipping

I do agree that the macro can be very loose and it does affect the sharpness of the picture. I wonder if this is because it is the lenses are less expensive then most
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