Cant focus to infinity on Letus

emretufekci

emretufekci

Well-known member
Hi Guys/Gals

We have 3 Letus Ex systems and we noticed yesyerday on one unit we could not focus to infinity using zeiss ZF 35mm or 50mm lenses. We did not have time to test the other adapters or all the lenses but I wanted to pop a quick question to see if anybody experienced this as well.

The 50mm wont focus beyond 10feet. I know thats not a lot of data but any ideas?

-Back focus was proper
-Unit was mounted and supported correctly
-Using a bartech FF
-tried in a air conditioned studio and outside 72 degrees

We have another shoot today so I will feed more data as I rotate adapters/lenses.

Thanks
 
Go to their customer service and request PDF manual. There are two ways: the easy way with the Nikon mount screws and the more pain in the ass way of having to open up the front end and adjusting the posts on the GG. If the former doesn't work, you must do the latter. In this case, I'd suggest slightly over compensating on the posts so you can later us the adjustability on the Nikon mount to cover your back focus from then on.

Line them up, get out your Allen set, order some pizza and set up a few focus charts.

On the good side, it can be done.
 
Are you sure that the bartech is moving the lens all the way to infinity? Have you tired disengaging the motor and manualy moving the lens all the way round?
 
There should be (has to be?) 7.5mm of space between the condenser and the ground glass. I just bought some calipers to adjust this.

If that doesn't fix your problem, then you need to start adjusting the lens mount.
 
When we had our previous Letus Adapter, we fixed this problem in a pinch by pulling the nikon mount out about a mm and retightened the screws that hold it in. It worked perfect so we could continue shooting. If your caught with that problem unless the backfocus is WAY OFF....give that a try and see if you can find it.
 
Hey Tim, Where did you find the link for customer service? Is is under the adapterplace site or letus direct. I'd like to get a manual just to have on hand. Thanks


Tim Naylor said:
Go to their customer service and request PDF manual. There are two ways: the easy way with the Nikon mount screws and the more pain in the ass way of having to open up the front end and adjusting the posts on the GG. If the former doesn't work, you must do the latter. In this case, I'd suggest slightly over compensating on the posts so you can later us the adjustability on the Nikon mount to cover your back focus from then on.
Click to expand...
 
He said "The 50mm wont focus beyond 10feet."

That means he CAN get focus up until that point, which means that everything is proper except for the Nikon mount backfocus. When the rear element of the lens is too far from the ground glass it will not be able to focus to infinity. And when it is too close the focus markings on the lens barrel will be inaccurate, i.e. you will focus to infinity before the lens marks infinity.

To clarify, if he can get focus at all (which he can, up to 10 feet) that means his HVX is properly focused to the ground glass inside the Letus, which also means that the inner components of the Letus are properly calibrated. The distance from the HVX lens to the ground glass never changes, so being able to focus to the ground glass does not depend on the focus position of the Nikon lens.


Marco
 
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Thanks guys for all the responses. I just got back from Chicago and have not even had a opportunity to pull any of the units out.

Leni: The 3 units were bought new about 6 months ago.
Huv: Thanks for the link
Kyle: I will try that as well thanks.
MArco: you are correct, up from 2" to 10 feet images are razor sharp on a 26" Panasonic monitor. Beyond that it will not focus. I will try re-seating the nikon mount.
 
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Thanks again for the advice guys, the problem was a poorly seated nikon mount. I think the issue generated from the fact we have too many of these units laying around and dont take them out enough.

Well DVXuser crew to the rescue.
 
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