I have the Letus Extreme along with several Nikon Lenses and Sony EX1 (all the most recent EX1 adapters -I just got the Letus about a week ago.) I have a 28mm and 50mm manual focus fixed AI lenses.

It seems I cannot focus beyond 30 feet or so with most of the lenses. I tried moving front Nikon adapter part to push it closer to the body, it really was as close as it could go, but moving it closer (if it were possible) seems like it might make it able to focus farther.

What am I doing wrong? I assume this isn't normal.

-Keith

Hey Keith,

Sounds like the ground glass screen is to close to the Letus body. If you are comfortable in getting inside the Letus, here are some instructions to adjust the screen. (Info passed along from Aaron.) It's fairly easily, just take it slow, and try not to touch the ground glass screen or any other glass inside.

1) Remove the front tube
2) You will see the plastic ground glass holder. Using a ruler or calipers, carefully measure from the back of this black plastic to the surface of the adapter behind it. It should be 7.5 mm all around.
3) If you find this distance is off, very gently push / pull the 3 metal stand offs holding the ground glass holder in or out to achieve a distance of 7.5mm all the way around.
4) If you are already at 7.5mm and your focus is still off, then adjust each of these to be slight less or slightly more all the way around.
5) If you cannot achieve focus at infinity at all, then you will want to pull the stand off posts out very, very slightly more than 7.5mm
6) If infinity focus is hitting before you reach the infinity mark on your lens, then you will want to push the stand off posts in very, very slightly to be less than 7.5mm.

Thanks for the advice, I took the front tube out, seems like a pretty simple procedure to either push or pull on the GG holder as it is in rubber bushings that are just held to the posts by friction. They seem to be right at 7.5mm spacing. Before I proceed with the 'trial and error' part. If I can focus close but not to infinity right now which way should I start, pushing to reduce the 7.5mm distance, or pulling to increase from the 7.5mm distance?

I assume I'll be 'pushing' rather than pulling for my problem. So this is a push a little, re-screw it together, mount the unit test, etc?

Seems somewhat time consuming but I guess necessary. -Keith

Keith,

It is a bit of a trial and error procedure. If the 7.5mm doesn't work, then pull it out just a bit to get your infinity focus. Don't pull them out too far, you might disconnect the posts from the rubber mounts. If you do, follow these instructions. (Also provided by Aaron.)

NOTE: If you accidentally pull a post out, here is the procedure for getting the rubber feet re-seated in the adapter:

- Completly remove the GG holder being careful not to put tension on the wires going to the motor
- Pull the 3 rubber feet off the aluminum posts.
- Use a toothpick or other skinny object to stuff the rubber feet back into the holes of the adapter. Make sure they are right side up and well seated in the hole.
- Once the rubber feet are mounted back in the adapter, push the 3 posts on the ground glass holder back into them.

In your case, you would want to pull the screen away from the Letus body. If your infinity focus is short, and you can't push your lens back any further, then the screen must come up to the lens.

Hope this helps,
Damon

OK I did it and now I can focus to infinity. It's a pretty touchy adjustment and one thing I want to mention which I really didn't understand even after the explanations is that the pushing and pulling doesn't affect the grommets which are visible and attached to the ground glass carrier. I thought that was was going to be moving the posts around these visible grommets. No, the grommets are held pretty solidly because the posts are machined narrower under the grommets and this keeps the grommets from slipping off the ends of the metal posts.

The actually movement happens inside the unit, beyond the holes the posts go through and I really couldn't see what was inside the holes, I assume grommets but on smooth parts of the posts. I also didn't know how far the posts went past these hidden grommets so it was kind of scary pushing and pulling. You really have to be gentle but quite strong to get any movement out of the posts.

I had a precision caliper with a dial to measure the existing distance from the Ground glass carrier to the body. In fact it wasn't even the same at each post connection point so I assume it works best when it is completely parallel.

So I pulled a bit, still didn't focus. Pulled more, this time to far and I could focus beyond infinity, pushed ever so slightly in and that got it. We're talking about a 10 thousandths of an inch of pulling out to make it work for me. Thanks for everybody's advice on this one. I'm wondering if this a normal and periodic adjustment I need to make as it seems that this must have gone out from being shipped, as I assume this is calibrated at the factory.

I'm glad I read this... I'm having the exact same issue. Ouch, sounds like it should be fun. I've already had to remove a big dollop of glue that had dripped and was keeping the GG from vibrating.

I'm glad I read this... I'm having the exact same issue. Ouch, sounds like it should be fun. I've already had to remove a big dollop of glue that had dripped and was keeping the GG from vibrating.

I'm glad I read this... I'm having the exact same issue. Ouch, sounds like it should be fun. I've already had to remove a big dollop of glue that had dripped and was keeping the GG from vibrating.

jesus.....definitely not looking forward to this.
count me in as another person having this problem with back focus....

I tried this and still can't focus more than about 20 feet. I pulled out the posts as much as possible but kept disconnecting the rubber mounts. So I'm out as much as possible. Any other possible problems causing this?

Dlee_ultra,

What type of lens mount are you using? Is the mount set right up against the adapter or do you have it pulled out a bit? Also, what type of lens are you using, and have you tried a different one?

I have the M42 screw mount w/ Takumar lenses. The 135mm is fine because I'm focusing within 20 ft. The 55mm has to infinity focus around 18 ft & it looks almost focused. That seems to be the problem. It just seems I'm close to infinity too quickly when I'm around 18ft away and the lens is showing over 30 ft.

I also got the improved Nikon mount but I currently don't have any Nikon lenses. I'm now thinking Letus adjusted everything based on the Nikon mount instead of the M42. You think this could possibly be my problem?

Word of advice from someone that JUST screwed this up... if you have to remove the rubber boots from the mounting posts too many times, the boots can - and in my case DID - tear. This results in halting all progress on correcting the focus issue and makes the adaptor itself useless.

No response yet from Letus on how they will respond to the request for new boots.