EX1 and Letus Extreme with PL Mount Focus Issues.
 

I haven't been able to achieve consistent focus with the EX1/Letus and PL mount. Infinity focus was never achieved.

Wider lenses were especially difficult. 18, 25, 35 - It's was strange you could get focus at about six to eight feet, but beyond that nothing.

Longer focal lengths seemed to work ok.

I know many people have had success with this set up. Any suggestions?

The ground glass was sharp, and we had all the latest EX1 pieces from Letus and Zacuto.

just a question...

It has been my experience that wide angle prime lenses generally have a very long dof.

If this is true than is there any point to use the Letus with such short lenses???

Incorrect backfocus adjustment is notorious on all the adapters and will be worst on wide angle lenses. Contact Hien Le at Letus and he will hopefully run you through a method of back focus adjustment. This is a major flaw in the design. It should be easy to set backfocus yourself on.


Steve - DOF is deeper on a wide but there are many reasons to want to use them with a 35mm adapter
1- It is still much more shallow than the stock lens.
2- If you need a wide shot in a sequence where you are already using a 35mm adapter you need to maintain a consistent look.
3- You can get wider lenses than the stock lens.

Lenny Levy

Thanks. Will call Letus. Hopefully there is a dependable way to adjust backfocus so that it doesn't have to keep being re-adjusted. It's such a time killer... we ended up having to remove the adapter and shoot with the fixed lens for the wider shots, which as you can imagine doesn't really match.

Also, I noticed that the whole adapter has a tendency to spin on it's own mount even when the alan screws are fairly tight. The screws are just tightening against a flat surface instead of into a thread... so by the time you get the 35mm lens, mattebox, filter and follow focus (weight)... the screws don't hold.
anyone?

I contacted Letus about backfocus and got the following instructions:

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

This procedure, while a little bit of a pain as it involves a lot of trial and error, worked perfectly in achieving spot-on backfocus with the Nikon mount - I haven’t had an opportunity yet to test it with any PL mounted glass. I will note that precision is key in that you want to make sure that the three posts are pulled out equally so that the ground glass is flat to the focal plane.

Adjusting backfocus is similar to the M2, but, in my experience, I was never able to get as good an image with the M2. My only complaint about Letus is with the company in regards to their customer service and more directly their customer communication. That said… I have been very pleased with the quality of the Extreme.

Well this doesn't sound good. It sounds harder than with the M2 because you have the extra work to get the individual posts on the same level or your edge to edge focus will suffer. I wonder why this isn't done properly in the factory? If you buy it with a PL mount and pay for the mount to come installed, one would expect perfect back focus at the right FFD.

And then people say the Mini35 is over priced. It is not. It's just well made and plug and play. You never need to mess with it. You just put your camera on and shoot. What you pay for is precision, which the more affordable adapters all seem to lack. They all seem to need a lot of messing around. I was hoping the Letus Extreme would be different. I hope this is just one case and not the normal.

I'm not happy with this process. It sounds far to wishy washy to depend on when you're on set and really need things to WORK and work well.
I'm going to give it a try and see how the process feels and what kind of results I get. If I'm still not comfortable with it, then I'm going to send it back a get a refund. I would much rather pay the extra money and have something that works or just not own at all (and rent) - bummer.
thanks everyone.

For my 2 cents, I can say that so far I have been very happy with the EX1/Extreme combo - I say so far as I have only had both for a pretty short period.

I had an M2 with an HVX and could never get anything close to edge to edge sharpness. Even after having the optical bock replaced to have it ‘more’ centered down the barrel, I still had soft edges. Additionally, the spindle running through the M2’s ground glass wasn’t set perfectly perpendicular to the focal plane, So even though I had the backfocus spot on, when the adapter was running, the ground glass would spin slightly closer and then farther in relation to the camera’s own lens with each revolution… Creating vibrating focus. This was an issue that wasn’t perceivable at normal speed, but at offspeed at 60fps… Very noticeable.

I’ve also used the both the pro and mini35s, and I will certainly agree that they are very well built - in fact, due to their robustness, they are the only adapter that I will rent from a camera house, although I would like to try the Movietube. However, the mini35 and Movietube cost a lot more than the M2 or Extreme. The mini eats more light than the cheaper adapters, and while it is better engineered, a short at the battery mount plagued my last shoot with one, and cost me a number of great takes when the ground glass stopped spinning mid-take. This, along with the fact that I find the mini’s oscillating ground glass noisy, is the reason that I purchased the extreme.

The thing about all of these lens adapters is that they are all work arounds… And ad hoc solutions…. Again my experience with some change…

I forgot to add that with the Extreme, I didn’t find adjusting the posts equally to be that difficult at all.

that's good to hear. I'm going to give it a try and see how it sticks. I basically want to know (and experience first hand) that I can get the adapter to be IN FOCUS consistently through out a shoot. I don't mind checking back focus once in a while... but if I have to completely take the adapter apart every time I change a lens, or bump the camera, or move the camera or what ever than that's going to be a total deal breaker. I don't mind working out a few kinks though. we shall see.

Tom you are working with Nikon right? Cine lenses are much more of a problem when it comes to back focus at wider focal lengths.

It seems I will be playing with a Letus PL soon. I'm looking forward to check if it will also have the back focus issues.

Yeah… So far, only Nikon. But I’ve never had an issue particular to wide cine lenses and backfocus. Perhaps, I’ve just been very lucky, but it seams to me if the actual lens is correctly collimated, then it shouldn’t be any different from a longer lens and the correct FFD. But if I’m wrong, please correct me…

The only potential backfocus issue that I’m watching with the Extreme at the moment is can the vibrating ground glass vibrate out of backfocus? My concern stems from not knowing what is actually holding the posts and thus the ground glass in place. I will say that when I adjusted the FFD, I did find it fairly easy to manipulate the posts. Again, this is not a problem I have had so far in my limited use of the Extreme or even heard of, but something I have an eye on.

Please let me know how your shoot with the Letus and PL goes. I had a job coming up that I actually purchased the Extreme for (Ex1/Letus/S4s), but it’s now gone back to the original plan which is film… Which is cool, but I am very curious so see how the system plays in production.

Well, not very well. I got to test it during the weekend. It makes very sharp pictures but I was quite disappointed with the engineering and design part at times and also somewhat the build, although this is just referring to the PL mount itself. The PL mount although it "worked" I found it quite flimsy and temperamental. I like the M2 PL mount much better(although the Letus Extreme adapter runs miles around the M2). I think it is better designed and made. The Letus PL mount felt like one of them cheap knock off accessories from India that you can buy on ebay. It doesn't even feel like aluminum. More like die-cast or something.
What I didn't like about the design was the way the mount attaches. Just three screws that you tight against the mount. No threads or even holes. Quite flimsy and inaccurate. By the way, you MUST have rods. I have read people saying you don't necessarily need them but that is just not true. Without rods, every time you tight (and otherwise) the mount the whole adapter will spin and get out of alignment. The whole connection through the filter threads is already a big design flaw in my opinion. Not stable enough, flimsy and risk damaging the filter threads and lens. But that is also how the other adapters connect.
Now the thing that really is annoying and quite unacceptable if you want to claim to be a professional tool is that infinity focus was not right. Even though the instructions that come with the adapter said the focal flange distance is adjusted at the factory this is just not true. The owner of the adapter shoots mostly with Nikons so he doesn't seem to care much and his widest PL is just a 50mm. But I took a 35mm and a 18mm PL and they wouldn't focus to infinity. I know they focus to infinity just fine on an Arricam so the problem is clearly the Letus. But then when I re-read the Letus instructions I found out the problem. They state they adjust the FFD at the factory using a 50mm lens. What a "unwise" move if you ask me. :( You should always adjust that with a wide angle lens since it's more critical with them, then the longer lenses will be all in focus too. A 50mm is hardly a wide angle. This is surely the reason and it shows the inexperience and somehow amateurism of the company. They are clearly not well rounded when it comes to real cinema lenses. Not surprisingly as all these cheaper adapters are more of a prosumer/cool toy thing than a real pro tool made to be dependable and to work without flaws, and the fact they are all mostly specialized in using still lenses for motion photography shows that. Also because all the compromises they have. At least now they are starting to overcome some of these compromises, like including a flip function etc. Things that the Mini35 always had. All together, the Mini35 is just much more professional, well thought out and works out of the box as it should. I have shot hundreds of times with a mini35 and I have never needed to adjust the FFD or have it failing on me in any way. Besides that, the Mini35 feels much more professional and is plug and play. Feels as well built as an Arricam. But it cost a lot. I would never buy it. But for rental it's the best option. I don't even think any of the cheaper adapters would survive rentals.
The saying is still true when it comes to 35mm adapters. You get what you pay for. Get a Mini35 and it will work. People who shoot professionally and can't afford to have things not working as they should on a shot will pay the premium. That's why P+S is still in business. Hobbyists and lower end professionals will put up with the compromises, lack of quality and design flaws to save some money. I was thinking of buying a Letus Extreme but I guess I will continue to rent a Mini35 when I need a 35mm adapter.

Come to think of it, this is not much of a fair comparison. P+S makes parts and accessories for high end film cameras. I doubt the Letus company even has a collimation bench. But for what is worth it, here are my impressions since you asked. Having said all that, if you can manage to focus your lens or have some time to waste messing to fix something that should have come right from the factory, the Letus Extreme makes one of the sharpest images I ever seen from a 35mm adapter.

I attempted this process and DISASTER I am now dealing with. First of all, when pushing the post into the adapter 2 of the 3 posts just bounced right back. They were completely unadjustable. Then as I feel like I'm finally making some progress the top suction POPS OUT! Now my gg screen is just dangling by the bottom posts. Is there any secret to getting that suction foot back in the little hole? I'm 3 hours in and no dice.

Quite an unintuitive process and especially annoying as an hour later I find out that Letus has released a new Nikon mount with a much easier back focus adjustment (why did they not let me know this product was an option and now available!!!). I really love this adapter but its starting to get on my nerves for sure. First I get sent an adapter with a cracked front tube, then the EX1 optimization kit that I pay $350(!) for doesn't give me edge to edge sharpness and then I'm told I need to adjust my gg screen which was supposed to come factory pre-set. The more I deal with them the more I feel like I have a returned/refurbished adapter and that doesn't make me so happy!

Wow. This is bad! I wonder when Hien or Quyen will chime in to address this? Are you guys out there? Some customer service would be nice.

I've decided to return my Letus Extreme adapter.
I'm going to take the "MOVIEtube Jr." lens adapter on a test spin... it cost much more (5K) but I have a feeling it's built like a tank. Will report back.

http://www.abelcine.com/store/produc...ductid=1000224

It looks a lot like the Letus Extreme, which in turn looks a lot like the Pro35. But the Movietube Jr is closer to the Letus than the Pro35. It actually looks like an better built and improved Letus Extreme. I can see just by the pictures that it's better thought out, like the back sleeve that goes over the lens rings ala Mini35. Interesting option. Can't wait to use one.

I am a little confounded by the method proposed for achieving backfocus by moving the pillars.

If this is necessary, my personal preference would be to make small packing shims made to shove into the bottom of the pillar holes to keep the pillars from moving forward deeper into the holes after adjustment. Getting them out again would be difficult. They would need to be paper or cardboard so they could be destructively removed with a pin end.

However. First things first. Caveat - I don't know if the Extreme-front end is similar to the older Letus35 with plastic front-end.

I am assuming it is so here goes for some instructions on getting that pillar rubber back into the hole.

Backyard tools needed.

Two free steady hands. (Have a hair of the dog if you have the shakes). -

Get somebody else to hold front-end or secure it with a vice or geeclamp onto the kitchen table.

Small wornout flatbladed screwdriver or kitchen dinner knife with blunt round end.

Heavy duty tweezers or good ratnose pliers.


Okay. Letus front-end is firmly secured. Now gently offer the rubber up to the hole. The sod won't go in. This is perfectly normal. It would fall out if it was a slack fit and it would not be a good look.

Now use the pliers or tweezers to gently incline the pillar sideways about 10 degrees as you offer one edge of the rubber into the hole in a sideways movement.

Keep a very slight pressure upon the pillar in an inwards direction or have an assistant put a little bit of thumb pressure on it, but not hard because the rubber will ride over, spread and try to turn inside-out, just enough pressure that what you have already offered up stays in place.

Now, whilst keeping that pressure and the inclination in place, gently use your blunt screwdriver blade or blunt knife to ease the edge of the rubber over the edge of the hole, working from one side to the other.

You can rock the pillar a little bit to help this process along.

You will eventually end up with just a little bit of the rubber hanging over. Use the blunt screwdriver or knife to push this in, at the same time put a bit of sideways pressure on the pillar itself to compress the rubber already inside the opposite side of the hole a little.

Once this last piece of the lip goes in, you can press the pillar into the hole. Don't just leave it there as it will likely pop back out inder air pressure.

Work the pillar in a circular direction like the groundlgass panel is meant to move as you keep the pressure on. Eventually, built-up air in the hole will leak past.

You may need to use a blunt dressmaker's pin to slide down around the rubber to let air out but make sure you don't puncture the rubber itself otherwise it may be inclined to come out during operation of the adaptor.

If it is inclined to work loose in operation, bringing the rubber back upwards in the hole slightly and placing a small spot only of yellow contact adhesive around it with a tooth pick and pushing it back in should be enough.

When messing with the contact adhesive, stuff a piece of tissue in the hole leading to the front glass and tape a paper wrapper around the groundglass carrier. You do not want strings of contact adhesive getting on them.

There should be a cottonthread-thin ring of yellow stuff left around the rubber. This should be enough to make things stay put.

An alternative means of insertion of the pillar is to find a piece of small diameter clear plastic tube to use as a compression sleeve.

Wet it with a small amount of water with bathroom soap dissolved in it. Place this around the pillar rubber. You may have to split the plastic tube and trim a little bit out of it for it to fit tight enough.

Tie a thin piece of electrical hookup wire around the tube to squash the rubber, then offer it up to the hole and try to push the rubber out of the tube into the hole.

If you are clever enough, you may be able to make a similar cylindrical compressor sleeve out of a thin strip of spam can or any other thin metal and leave two little elbows folded out on the ends which are only very slightly apart when compressed around the pillar rubber.

Use the ratnose pliers to squeeze these ends in to compress the rubber then offer it up to the hole to slip out of the piece of thin metal as for the plastic tube.

I found it easier to use the blunt knife method once I got the knack of it.

If you get the rubber back in, make sure all the pillars are pushed back into their holes fully and the rear of groundglass carrier to front face of front-end measures the same at all pillars.

Now back to your PL mount.

Again, I am not familiar with the Letus Extreme so I cannot vouch for how far the groundglass rear face is back from the front of the Letus front-end. While you still have it in pieces, use a vernier caliper to measure from the front face of the front-end to the rear face of the groundglass.

You can buy plastic verniers cheap from your handyman store.

If the Extreme is the same as the older Letus, it will be 40mm from the front face to the rear of groundglass panel.

Assemble the front-end with the groundglass carrier, etc back into the tube.

Measure back 40mm or whatever the Letus Extreme groundglass rear face distance for the Extreme happens to be, then scribe a very accurate mark on the outside of the tube body or use a piece of masking tape if you want to keep it looking pretty.

This will be your focal plane.

Now take your PL mount. Screw the clamp ring home, then using the tail of the vernier, measure from the front of the clamp ring to the bottom face the lens with its wings butts up against (the lens flange face). Write this distance on a paper.

Offer your PL mount into the Letus and measure from the front of the clamp ring to the scribe mark on the tube body which is your focal plane. The correct distance should be 52mm plus the distance you have written on your piece of paper. You could do this with the Letus front-end and groundglass carrier out of the Letus body but your chances of damaging something will be pretty good so my personal preference is to have the front-end secured back inside the body for this task.

In the case of my mount, the clamp ring to bottom face (flange) is 5mm, so front of clamp ring to focal plane mark would be 52mm plus 5mm which is 57mm.

This process will put you in the ballpark of correct flange to focal plane, so long as you are able to get the mount tail into the Letus body far enough back.

It is my guess you will need to have it forward of full rearward insertion like the old reversable Nikon-Canon mount. If the tail of the PL Mount is too long to enable you to get it far enough in then something may be wrong I cannot help you with.

To establish correct backfocus from this point on, everything I have mentioned in the sticky thread for Letus XL should be valid.

It will be helpful to make up some round packing shims from cereal pack carboard or icecream pack plastic to go between the tail of the PL mount and the internal face of the Letus to help keep things square and help get it exactly right in the future should you have to remove the mount. The way these work can be seen in the YouTube clip I posted which is linked in the lowermost post of the Letus XL sticky thread.

this is funny. I paid like 1500 bucks to Letus so I can go through this process? I love it! About half way through I couldn't figure out whether or not this post was a joke... this is a joke right? If it's real then I'm impressed with your ability to re-engineer the Letus and if it's not then I'm impressed with your sense of humor. Either way I'm happy to pay more for something that works and works well.
5K for the movietube is fine by me... although, I think I missed the fact that it doesn't have a PL mount? Anyone?

Michael, I believe Bob was genuinely trying to help. He's a very nice guy and one of the most helpful people around here. He always takes the time to write as thoroughly as possible and he is extremely knowledgeable about 35mm adapters.
It isn't his fault that Letus slacked on their job. ;)

I am not joking and admit I initially was a little cross about being thought to be a jokester but that is my problem to deal with.

I am seriously offering this advice at expense of an hour or two of my life which might better be spent on making money, sleeping, breaking bad wind or whatever.

US$5K for the Movietube is going to get you a very robust, precisely engineered, stationary, not moving groundglass system.


Back to the Letus Extreme.

I am not about to go in to bat for the Le brothers. They are grown lads and can look after themselves.

The original Letus was a improvised build by an enthusiast for enthusiasts at an affordable price and who in the large accepted that there was some final trim and adjustment required of them to get it working best.

Current build quality is more robust and precise and this is reflected in the added costs now asked. The product is more sophisticated but is not so sealed up and locked down that enthusiasts cannot get inside and tamper to their heart's content.

The Letus Extreme I cannot yet speak for as a turnkey proposition out of the box as I have not yet got my greasy hands on one.

I found that the early Letus35 with some tweaking could yield pleasing images reliably. A P+S Technik Mini35 it definitely was not but the image was to my view within the last ten percent qualitatively in some of the lens-in-camera versions.

There are people doing serious and good work with the Letus Extreme, happy with what they have and content to live within its means.

If you do not have fine motor co-ordination and mechanical ability, then maybe it is not for you. From time to time, secondhand Mini35-400s come onto eBay in the US$6K to 7K ballpark and 300s at US$2k to 4K.

Bob.

Please accept my apology. It was not my intention to poke fun at you, really I mean that. Rather I was genuinely shocked at how in depth the process was... not to mention the skills it takes to figure something like that out. It was so detailed in fact that initially I couldn't tell if it was a joke. It's a rare kind of post. Now having read it again, it's clear that it is no joke.
Thank you for taking the time to offer this solution for Letus owners.... and thank you for taking the time to figure it out in the first place. If I have offended anyone else on this board than please forgive me.
best,
michael

Michael.

No hard feelings. Sometimes I lose the plot a little in translating from american to strine and sometimes turns of phrase in strine are misintepreted by americans, particular example being our use of the word "mob" which here does not exclusively mean the mafia like it does in the US.

I have taken the liberty of emailing Hien Le with a link to this thread so hopefully he, Quyen or Aaron will respond soon, though with Easter fast approaching, next Tuesday or Wednesday might be a more reasonable bet.

The moving-of-the-pillars thing might have been a much earlier suggested solution relating to the original Letus35 and I am surprised it is still being propagated.

Again I state that it would not be my preferred method because this part of the whole adaptor is where the build precision is pretty good and moving the groundglass itself also has a collateral effect on the camcorder focus via the dioptre.

Back focus
 

Hi all,

The instruction is for the people we feel are handy enough to do it. Please do not use other's instruction that may void the warranty. We are behind the product and if you call us, we are more than glad to walk you through the process when we think you can do it. Anyway, there is a trick to put the black rubber feet back. You need to use a tooth pick to stuff the rubber feet into the hole first, then push the silver post into the rubber feet, then pull it out to the proper back focus level. The process, if done properly, takes about 10 seconds, if not done right, you wouldn't even get it to go in if you have the rubber foot on the silver post and stuff both in at the same time. Bob is right, you can use the shim method like P+S Technik is using for the their product. Moving the posts in/out is more of a permanent solution (done once), but it must be done right. The new Nikon , PL and Canon EF mounts has the 3 little screws on the back of the mount, so you can use it instead of the shim.

One more note, we do not read forums often. This was brought to our attention by Bob (Thanks Bob) and the best way to contact us is by email or calling our toll free number.

Thanks,

Hien