Steve, when will you be getting something on your blog about aligning the GG? think that will be excellent. I'm really hoping you shoot video of it for us :)

I've had a ton of issues over the past few days getting my focus adjusted properly but I'm getting much closer. A few videos would be awesome. Thanks for all the info you guys have been putting on here!

I need to do that, thanks for the reminder. Heading out to NAB so it would have to be after that.

Do you have hot glue on your motor shaft? I have gotten a world of difference with it not being there.

Here is how I adjust back focus... see pic.

Also here is some more back focus techniques using a Red Camera and a Nikon lens http://www.youtube.com/watch?v=pRicc1HU44c

We do not have easy way to adjust the Letus, except to pull it apart.

Hey Steve,

Thanks for the pic. I just got a set of calipers tonight and got everythng measured up right now.

What do you mean by hot glue on the motor though? I'm curious bc when I got my Letus the other day, the first thing I found when I had to crack it open was that there was a large amount of it that actually sealed it to the wires on the base. I cut that away a bit and my vibration got better.

Do you mean though that you actually removed as much glue as possible? I'm really interested in that bc it seems it would give a much cleaner vibration than that unmeasured amount of glue that is still on there.

Thanks for the help!

EDIT:
I also just noticed in your pic you have a bit of hot glue on the tip of the motor as well. Was that there for you when you received it?

Steve,

Not backing off from what I said my opinion on the LEX quality is, I must admit your pictures and hints are invaluable; thanks for that. I didn't decide to put mine apart yet (waiting for what Aaron answers me), but it doesn't look that complicated.

Looking at those photos, and reading about pulling the three stands to get the gg plane in the right distance from the base, I wonder:

- assuming I manaage to adjust it for back focus at infinity, how long will it stay in the new position? I mean, the 3 stands should be threaded or something, so that - by turning them - one could easily and precisely adjust the distance, and it would be permanent. From what I understand, by pushing/pulling we're just using the rubber elasticity, or what? How is it supposed to hold after adjustment? Thanks in advance for your clarification.

I can answer that a little :)

The stands all have rubber feet that wedge into bored holes in the case. They are tight too. If you pull them out or end needing to for some reason, they suck trying to get back in. I went with the one recommendation of a toothpick - which works to help guide them back in - but dont do that. It flakes and then you end up having the pull the face off the letus to get the chip that went under the condenser and wont budge no matter what :(

Anyway, they do move, just very inaccurately. Maybe in the future, Quyen will come up with a pin that has a rubber elbow on it and a threaded base for adjusting. That would be cool.

But to finish the answer, it seems like it will hold fairly well. I imagine after a while it'll need readjusted. So make sure you have a set of calipers and I also bought today a pair of needle point tweezers for model making to help should i have to bother with those rubber feet again. Hope that helps some.

The Letus EX came with the hot glue on the motor shaft, as seen in the pics @ http://web.mac.com/stevecahill/Steve_Cahills_Blog/Blog/Entries/2008/1/6_Letus_Autopsy_1.html

Some users have it some do not, mine is no longer there, it came off. I was told it is put on to set the vibration correct, but do not know what the specs are to determine this. With hot glue it is guessing game with a dap of glue here?

Note that the calipers with their sharp edges will take some paint off of the GG holder when setting the back focus. This will get on the glass, use compressed air to remove it, and or take the edge off of the calipers with some emery cloth to minimize the flaking of the paint finish with the calipers when setting the distance. I just wedge the calipers underneath the posts and square them up with the GG, this sets the distance. I cannot feel it move, but it sets it equal distance all around. I can image these rubber seats will wear, become stiff with age and will fail at some point. do we have a part number for their replacement?


I agree, a screw type back focus adjustment is in order, that will raise the price another $200.00 See http://www.youtube.com/watch?v=pRicc1HU44c
How RED Camera deals with back focus.

I just wedge the calipers underneath the posts and square them up with the GG, this sets the distance. I cannot feel it move, but it sets it equal distance all around.

Excellent idea, Steve - if I decide to do it myself, I'll use it, as my adjustment most probably requires increasing the distance from base (i.e. moving the GG towards the lense, to achieve infinity focus). Thanks!

PS. But still, this is pathetic! Would you dismantle and "adjust" like this a $2,000 lense, for instance? I bet you wouldn't... Well, the Letus is also part of the duct the picture enters your camera through!

I agree, a screw type back focus adjustment is in order, that will raise the price another $200.00


Well, Letus could make a precise adjustment much cheaper for us, by providing the lense mounts with a bit thinner flange, and a set of spacers to be put between the mount and the adapter - this way, by adding or removing spacers, easy and permanent adjustment would be possible...

But pulling / pushing within the range that some rubber will allow? Or balancing vibrating parts with some glue drop?

C'mon, Letus!

OK, I know what you are talking about now. Mine does not have the glue on the tip but it does have a ton of glue around the base front side of the motor - as well as the back. I see yours has the glue on the backside and is clean on the front. I mean I have a large amount here, I wonder if its necessary... I'm wondering if I would get a performance boost. In my tests in bright lit sun or in shadow, I cant stop down past 2.8 on most of my lenses and get away with a pan or tilt. Any thoughts from anyone?

Any thoughts from anyone?

Just one: even more disappointment.

Piotr- I feel your fustration. Perhaps you can offer some additional advice to Letus, and perhaps his device will not fullfill your needs. I am trying to make it work. I have ran into every obstacle with this device and have found a solution, hopefully these solutions and best practices will be implement into the LetusEX II.

Now some more best practices you need to know.

Never stop down the Sony EX1 camera lens to anything over F 5.6. Why?
Do this, go outside with the camera aim the camera for the sky. The Letus taking lens I will call it the Nikon lens in this case should be stopped down only 1 stop. The Sony EX1 close down to F 22, use or do not use the ND1 or ND2 on the Sony to get the Sony F stop so it is closed past F5.6 focus on the sky. Shoot starting @ F 22 start to open the sony lens one stop at a time until you get to F5.6. Take this fooage and look at it on a large monitor. Do you see spots?
I have spots on the Letus glass prisim, that I can not get off, and they are only visible when the Sony is @ above F5.6. This is true when shooting sky and or a light colored background. I do not use any F stop on the Sony that is over F5.6. If needed I use the ND on camera or before the Nikon lens to avoid the issue of seeing Letus spots, too much DOF. You have more flexablity when NOT shooting plain sky or backgrounds.

The other issue; do not bother to stop down the Nikon lens more than 2 stops from open, as it in the sky exsample above increses the DOF and the grain of the vibrating screen becomes more visible, and serves as a technical flaw. The SonyEX1 Lens stopped down too much increases DOF and shows dust spots inside the adapter.

So a few rules of the game to play by.

Let me know if any one can duplicate this by stopping down. Here are some sample pics showing the dust spots at F 11-16 on the left and no dust on the image on the right @ F 4-5.6 Dust is on the left side of the video grab & is very visible.

I see the dust for sure. One question for you though Steve, how can stopping down the Sony create more DOF? Shouldnt that only be possible with the Nikon being stopped down as we're merely capturing an image from the GG into the Sony imager?

The tests I've been working on are actually trying to lengthen my DOF more. I'd like to operate at times with an f-stop of 4 to 5.6. Seems like I may be able to get away at times with 4. I'm working on an After Effects fix to see if I can make it work.

BTW, I'm working on this idea in AE where I am taking footage of the plain GG vibrating - taking it to B&W and inverting it and using it as a reset mask using add or screen to bring back up the dark areas. I then level and reset the contrast. I'll do some tests once my sched clears and have to post results.

How are you an Phil getting a deeper DOF in your shots? Such as Phil's stuff from New Mexico that showed some nice deep focus on the tramway piece.

Steve,

Thanks for your excellent hints, again. Yes - even though I only have a very basic experience - I can confirm most of your observations. When clear sky occupies considerable pat of the scene being shot, one must be very careful with the shutter speed and aperture combinations, as the GG can become visible. One thing I can say in favour of my own particular Letus unit is that there are no spots whatsover - all I'm getting (when shutters is too fast, or the prime stopped down) is some film-like, uniform grain; actually could be used for artistic purposes.

What do you think of my idea of using bushings/spacers/washers (whatever the right English term is best for it) under the lense mount's flange for backfocus adjustment without messing around with the adapter's innards?

Let me know if any one can duplicate this by stopping down. Here are some sample pics showing the dust spots at F 11-16 on the left and no dust on the image on the right @ F 4-5.6 Dust is on the left side of the video grab & is very visible.

Yes, I had this problem big time. When I got my LEX it was still snowy in Finland and on a sunny day all you're shooting at is basically white. So i needed to stop down to f16 with ND2, thats bright I tell you! All the footage was totally useless as it was just full of this gg smudge.

Now that the snow is gone my problems are gone as well. But I do have an ND filter to stick in front of the glass (the Coking ND gives me weird red issues talked in other posts though).

,how can stopping down the Sony create more DOF?

It doesnt create more DOF in the image you are seeing but it creates more DOF to the ground glass of the letus. I bet someone more techinacal can explain why it is like it is. But I get best results with EX1 f stop around 4-6 just as Steve says.

Sami correct yes DOF to the Letus GG.
Remember we are talking about 2 lens here, The camera lens that focus on the rear of the letus GG and a taking lens that focus on the subject but puts its image on the GG for the Sony lens to focus on. Two DOF's that work independent of each other. Too much DOF and any dirt, spots on the Letus shows up, just trying to see where it is inside!

The new Nikon mount has some screws to adjust back focus but the old mount and the new mount are not the same thickness, the newer mount is thicker, which means the adjusting screws on the new mount push it out too much, the new mount needs to be thinner so the screws are at their min distant. If you make a adjustment the lens goes out too far, when we need it to go in, thus we have to pull out the GG to compensate. I had to adjust my GG when I got the new Nikon mount just because it was thicker. I think you could try to make a GG that is adjustable but with a rigid adjustable mount I think you would be introduceing new issues. But try it let us know how you make out and you will be in the adpater business. UGH... This is a big difference between spinner type adapters and vibrator type. Phil Bloom has a good FAQ called: "35mm Shootout" Read it @ http://www.philipbloom.co.uk/Philip_Bloom/35mm_Shootout.html

The issue is with the weaker part of the adpater which is the CG. It needs not to move, fixed, and stay that way through-out the life of the adapter. Or better yet buy a camera that makes use of NO GG does not have a add-on adapter does not have 2 DOF's does not have 13 surfaces to keep clean allows the owner to concentrate on making pictures and not adjusting this and that all the time, it is a digital video camera and is called Red.

Not to say Red has it own set of issues, which are being sorted out.

I have one more question to more experienced Letus users, and those with Canon FD mount in particular. I have 3 Canon lenses, and all of them are extremely tricky to be mounted. Is it normal with the FD mount in general, or is the Letus FD mount ring a bit, well... unperfect?

My FD lenses also take a bit of jiggling to mount...

It felt a bit fiddly before I learned how to do it correctly. I've used both the old and new FD mounts. There could be a little red mark on the mount to show where to start mounting the lens from, once you find it you can put a little marking there. Mount the lens 3cm clockwise from the marking, turn counterclockwise so that it clicks into place and then turn clockwise until it locks to the mount.

There might be some differences with lenses but in general I can change a lens with one hand very quickly. Hmmm... Would be a great competition, who can change their lens the quickest ;)

Sami

Thanks guys.

Once you figure out how it works, I don't think any permanent marking on the ring is necessary (after I managed to properly mount my first Canon lens, I just turned the mount ring so that now, the red mark on the lens should be in the uppermost position before turning). I must say though that the whole "operation" is still fiddly, and sort of non-repeatable, for me... In the mounting speed contest, I don't think I'd be the winner!

As to my other woes with the LEX, it seems Letus have chosen to stop answering my messages to them on their support site. Oh, well - I guess I must adopt this "made by enthusiasts, for enthusiasts" attitude, and start messing around with adjustments myself. Please take a look how badly my GG is twisted in the viewfinder (sorry for the quality - didn't care for right exposure at that moment):

- on the left, when just mounted on the rails without any tension applied to the mounting brackets/screws
- on the right, the best position I can get with the current rails support system under a maximum tension I'd consider reasonable (ANY tension will probably increase the vibration noise, though)!

I'll probably need to modify the front supporting bracket...

Or - since I'll probably need to disassemble my LEX anyway in order to adjust the back focus - is there a way to adjust the whole innards' angle in relation to the housing?

yeah, that angle does look way off. Just nicely and persistently mail letus about it, they will answer Im sure. Sometimes it can take a few days. I guess since its propably only one guy, Aaron, doing the mails so he must be busy.

Sami

yeah, that angle does look way off. Just nicely and persistently mail letus about it, they will answer Im sure. Sometimes it can take a few days. I guess since its propably only one guy, Aaron, doing the mails so he must be busy.

Sami


Agree, Aaron was great with getting back to me. He was ready to issue a RMA and still will right away if i have any more issues. I got them sorted out myself so no need.

Couple of days ago, Aaron has offered issuing RMA to me as well - does anyone know how it works from Europe? When first importing my LEX bundle, it spent 2 weeks at the customes, and I had to pay the duty and VAT an the total price (Fedex rate included !!!)

If you're after a cinematic look, trust me, once you get it working it is worth all the trouble :)

Does your letus motor shaft have a dap of hot glue on it? My did and it came off and I believe I am getting less artifact and sky issues when shooting a plain background like the sky. See my blog with pics showing the hot glue.

Never got a proper response about why the hot glue is on the motor shaft for balancing, and how that is calibrated.

The extra noise may be because of the extra weight on the end of the motor shaft, also check to see if any thing is loose, make sure those allens screws are locked down! With the absence of the glue on the motor shaft the unit is more quiet but still it make a buz- vibration sound which is normal.

Instructions from Letus site for adjusting back focus:

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.

OK, so I've found some time at last to try and adjust my Letus Extreme; here is the outcome:

- mine doesn't have the glue on the rotor shaft; instead, there are drops here and there on the GG holder itself

- as expected, the distance was well below 7.5mm (I suspected this, as I couldn't get infinity focus); I pulled the three stands out and it's now 7.5mm all around

- unfortunately, with the stands pulled out like this, to whole assembly now produces very high frequency rattle (or whine), which replaced the low frequency rumble/vibration it was making with original (factory) adjustment. Also, the GG has obviously changed the amplitude of its vibration - it's now shorter, hence the noise's higher pitch. It's this whining rather than vibration which is unacceptable now, after I made the adjustment to exactly 7.5mm!

- what's even worse, I still can't get true infinity focus!

All in all, this is extremely disappointing - how can an opto-electrical device worth $3,000 (yes - this is what it cost me after the duty and VAT), be so imprecise! As I suspected, there is no way to affix my unit to the camera so that the GG rectangle is level in relation to the camera, while the adapters "nose" is fixed to the rails bracket - it's simply machined not precisely enough. Also, after the adjustment I am now sure it cannot keep back focus even if I succeeded to get it right - the GG vibration would spoil the adjustment sooner or later.

Also, even though I was extremely carefully handling it, one of the glasses fell out of it - the glue holding it was so lousy weak!

This is so frustrating I'm considering to demand refund from Letus.

Sounds like something is seriously flawed... Perhaps you should go after that refund.

In my experience, the adapter is not an easy piece of equipment to work with when it comes to adjusting and then maintaining back focus - and especially not for the average person without any experience with collimation and shimming. I have been far from impressed with Letus's build quality and some of their oversights... Of course these problems are no different than those I've found in other inexpensive adapters – inexpensive when compared to the P+S or MovieTube adapters.

However for me… Despite being a pain, it does make a nice image… And as long as it doesn't compromise my work in the process, the nice image is what counts. I bought it to use on the same specs and low budget projects that I used to use the P+S on... My feeling is that optically, it blows the P+S away... And I'm willing to put up with a little extra work if it get's me a better image... I'm not crazy about the extra hassle, but nothing is free.

I have taken some pictures (with my mobile - sorry for the very poor quality; I was in haste), showing what happens to the front tube alignment with the front bracket after I turn the adapter on its thread ring in my EX1, so that the GG rectangle is level in the viefinder.

In spite of the poor pictures quality, it's obvious that - with the camera and the adapter on rails - I can either have the front bracket aligned and the screw tightened but the GG twisted as per the pictures I posted earlier in this thread, or have the GG level, but the front tube unable to rest on the bracket and the two connected with the screw.

I hope Aaron will address this obvious machining error...

Couple of days ago, Aaron has offered issuing RMA to me as well - does anyone know how it works from Europe? When first importing my LEX bundle, it spent 2 weeks at the customes, and I had to pay the duty and VAT an the total price (Fedex rate included !!!)

Hi Piotr,

This should be fine as long as Letus marks it apropriately (as 'no value' repair/exchange) as I'm sure they will. Be sure to keep your reciept for returning the 'old' unit; customs may ask for it (but I've never had them do so).

George/

Thanks George for reassuring - do you know if the RMA number as provided by Letus (in the form of just passing its value with e-mail) is of any meaning to the way customs may handle it? I'm asking, because a customs officer told me on the phone today that if I have it printed on paper, it will suffice to clear it hassle-free both directions - but I understood it's supposed to be a document, not just a number per se...

Apart from the customs procedures, what still holds me from sending my LEX back not being certain that what I'll get back will be completely flawless. Is it possible that all other units are OK, and I was unlucky enough to get mine plagued with all kinds of possible flaws?

Hi Piotr,

Just include a copy of the e-mail in the box (always good) and you could attach another one to the FedEx form. Usually I find it enough to mark it as "warranty repair" on the customs documents/shipping label. Letus will do something similar, and you should be fine.

You seem to have more than your fair dose of 'bad luck', but I believe you can expect to get the unit back fixed. The crooked GG seems really bad. I'd include a checklist of everything you believe is amis with the unit when you send it back.

George/

Not having any support from Letus, and with a very important project coming soon - I managed to make my Letus usable (far from perfect - the GG' stands pushed back in order to stop the whining, but at the cost of infinity softness; the GG not level but at least being able to fix the front tube on the rails, etc).

Now I am facing another problem: when setting the critical focus of my EX1, with GG stationary (and of course without lens), I cannot get the peaking to be even close to uniform over the whole frame. When it's on in the middle (only possible near the upper edge), it disappears at both sides; slightly turn the focus ring and it appears on the right side, but vanishes from the middle; it never appears on the left side!

Now, is this how the new, "improved" EX1 achromat is supposed to behave? I don't think so; in fact I have serious doubts whether mine is indeed the improved version (it came fixed to the main adapter body, not as a separate screw-on part). What do you think?

Another reason for non-uniform focus might be the GG is not planar; given the nature of push/pull actions involved in back-focus adjustment, and how crude and unstable that is - it almost seems impossible to ensure it's 100% planar!

And indeed - after I set it to peaking near the GG's middle area and put a lens on, my test shots exhibit considerable softness near the edges (particularly the right one - funny, because the left edge area has been impossible to achieve peaking at all, and yet it's much sharper with the lens on)...

Any comment welcome!

I'd be willing to bet that the GG position is the source of your focus problems. If rolling through the focus causes the peaking to move left/right, I'd say it is very likely the GG is shifted. These are very minute changes, and I'm honestly a little surprised about the crudeness of the adjustment. For some reason I remember Steve Cahill saying the improved Nikon mount has a depth adjustment?

-Sean

It does, kinda. You can push and pull it out slightly before you lock it down with the alen wrench