Help! My letus won't focus!

M

mrbrycel

Well-known member
Be rented a Letus Extreme about 3 times, and finally decided to buy one. I got it today and set it up like I have before, put my 50mm Nikkor lens on, and tried to focus. It wouldn't focus! I could see the focus shifting like it should as I pulled the barrel, but the most in focus part of the image, although more in focus than the rest of the image, was extremely out of focus.

I'm guessing this has to be a back focus thing, but I'm scared to take off the piece behind the mount and start messing with the ground glass.. What should I do??
 
Sounds like your GG is out of alignment. I was under the assumption letus adjust the backfocus for a particular lens manufacture (nikon, canon, etc.) before they send it out.
 
The ground glass is set at one position to work with everything. The mounts themselves are different lengths to account for the different required backfocus distances.

I agree with nantnee that your gg is probably out of alignment, though. I don't advocate trying to fix it yourself. It's not an easy adjustment to make. You've probably already done this, but just in case, check to make sure that the camera is focused on the ground glass, and try another lens to make sure your 50mm didn't somehow end up drastically out of proper collimation.
 
Now that you mention it, I was in a bit of a hurry cuz I had to go to work, so I just focused the HVX to 5.12, which was the focus point on the Letus I've rented in the past. It didn't occur to me that every Letus's GG may have a different focus point. I hope that's the issue. Does the focus point vary greatly between Letuses?
 
This sounds like the video camera isn't focused on the ground glass screen of the Letus. Its possible but unlikely that the Backfocus of the Letus itself would be that out of focus.

Focusing on the same point you used with another unit won't work. In fact focusing on the same point you used yesterday or a half hour ago might be off. Always check your video cameras focus on the GG often. It can change with temperature and the readings in the viewfinder are not precise.

Lenny Levy
 
mrbrycel said:
Now that you mention it, I was in a bit of a hurry cuz I had to go to work, so I just focused the HVX to 5.12, which was the focus point on the Letus I've rented in the past. It didn't occur to me that every Letus's GG may have a different focus point. I hope that's the issue. Does the focus point vary greatly between Letuses?
Click to expand...


Theoretically it should be the same *if* the units have the same achromat, have been properly set up, and gg is properly aligned. You'll get greater precision for this changing the focus indicator on the HVX to numbers instead of feet or meters. In actual practice, the focus distance can vary ever so slightly from unit to unit, and Lenny is right. Temperature (especially colder temps) can throw focus off just a little.
 
Thanks for the help guys. I'm so dumb.. it turns out all I had to do was focus on the ground glass. I assumed that because the other Letus's GG was set at 5.12ft, every letus would be the same. Mine turned out to be 2.76ft.
 
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