Up until a week ago I had used my Letus flip exclusively with my A1.

Now I am back in the UK I have connected it to my Z1. Ever since then I cannot get anything usable out of it. I can't even connect it back up to my A1 to check it out as it has gone in to Sony for repair.

Here is my problem...

With the a1 I never really new what the camera's iris was set to or how much gain was being used as it just uses something called exposure which is a combination of them both if you leave the shutter a 1/50th (pal)

Outside today, I took my Z1 and Letus fip with a nikon 28mm 2.8, 50mm 1.8 and 135mm 2.8 set of primes as well as my f2.8 sigma 24-70mm zoom.

With a 2.8 prime and a normal brightish semi overcast English Autumn day my lens was wide open, my camera iris was wide open (by zooming in to get full frame I lost a couple f stops on the camera so it says 2.8. It was underexposed, I had to put 9db gain in. Surely I must be doing something wrong, does the Letus flip really need that much light? The ND filter wasn't in either.

I am also getting this film of grain with every single lens, the zoom is worst but even the fast 50mm 1.8 had it, i had to have it wide open and camera wide open to just get the right exposure, at least i didnt have to put gain in like i did with the f2.8 lens.

I dont mind a little camera gain in as it is quite subtle on the z1 but it seems incredible at midday outside on a normal day i just didn't have enough light. Surely the f1.8 is fast enough yet even with that on there was barely enough light...

Am I being really stupid somewhere? Please help, it's driving me crazy, in the viewfinder you really can't see the film of grain but connected up to an HD tv, there it is, clear as day. Why can't I get exposure, it seems ridiculous!!!

Phil.

You are not crazy.

Light loss through any groundg;ass based image relay system will occur.

There have been tests by two DoP that I know of, one in Australia and one in the US.

System loss for lighting conditions which would require an f16 aperture apparently is almost zero. But at the wide end, the loss in the test subject was approaching two f-stops.

In the lighting conditions you observed on my demo, you might normally shoot that direct-to-camera with ND1, 0db gain, 1/100sec approx shutter, f5.6 to f11 manual aperture, depending on what in the shot you want best exposed and maybe ND2 if you want wider aperture or slower shutter. Don't regard this as gospel as there are a few things which invalidate this comment.

The cam I have been using has a couple of vices or it is simply my mismanagement of it. The automatic exposure seems to hang around regardless so I select slowest response time to avoid the pumping effect. The headphone socket doesn't work.

Whe I fit up my device, no ND filter or ND1, the aperture comes out to f5.6 to f6.3, 0db gain, shutter speed is best at 1/50 sec. This was for the SLR lenses set at aperture f4. This SLR lens setting will provoke groundglass artifacts in certain lighting conditions.

Sometimes the SLR lens and camcorder aperture can be changed interactively to move the artifact in the image to somewhere less evident.

With my CD-R sized disk, there is a grain artifact always in the form of a fine random grain like film emulsion. In lowlight, with +9db gain selected and especially with 12db selected, there is a lot of grain effect in the image.

With the Letus XL flip in recent tests, we found the fixed pattern was there throughout, very faint in good light, quite muddy on lower lighting with troublesome lenses.

With one very old Nikon zoom lens which had a very stiff notchy aperture adjustment and what looked like little bits of metal fragments inside on the glass, outdoors the Letus performed at its best thoughout the zoom range from wide right up to f22 even against bright late afternoon city sunlight.

On inspection of a high res monitor, the artifact was there but almost gone.

It was never visible in the viewfinder.

Thanks Bob,

In my shooting conditions I was just so shocked that I had to had both slr and camera wide open and a very fast lens to just get exposure. Then when I looked at the footage there was the grain...

I looked back at my a1 footage from Florida, the grain was evident throughout. I just couldnt see it that clearly on my macbook pro. On my hd tv it's got massive neon arrows flashing and pointing at all the nasty stuff!!!

So my problem is with my Letus, I can't play around with the slr aperture/ camera exposure to get the least artifacts as they need to be wide open unless there is bright sunlight...just wondering with the z1/fx1 whether anyone has created a picture profile for use with the Letus that more or less minimizes all these artifcats, perhaps there are settings inside the camera that hide them well...it's so random at the moment.

I am getting a Brevis35 and am really hoping that most of the problems I have having with my Letus will not occur with the Brevis. From the side by side review a while back this hopefully should be the case.

thanks

Phil

Had some much better results today...and I don't really know why...the artifcacts stiill there (wish you could see them in lcd or viewfinder!) surely the more open the slr lens the less artifacts i would have thought??

I opened it all up today to clean it and noticed the motor has a dollop of glue on the end that spins, I assume this is by design to make it start of something...if not I guess I should remove it!

Cleaning...for those smaller more obvious blemishes are they more likely to be on the macro filter if they are smallish and unaffected by slr lens focus?

new file called newletustest from today...its quite hard to see what I am talking about from the file...it is full rez so its a big one of 20+mb...its also only 9 secs long and very dull but any thoughts would be great (it is a bit milky, ignore that am after that static grain!)

http://homepage.mac.com/philip.bloom/FileSharing25.html

i am just wondering if I am expecting too much...it looks fine here on my computer, well it looks ok. On my 37"hd tv it looks crap.

Should I really expect static grain free sharpish hdv pictures out of a DOF adaptor?

Phil.

Don't remove the glue. The motor shaft itself is quite thin and might damage and the GG position may be altered by the brutality needed to get it off. If however you do remove the glue use pinch type nail clippers.don't try to shear it off with a knife or razor blade.

Maybe also shoot some direct-to-camera with long zoom settings, include plain sky or painted wall as an out of focus area, shoot it over and under by using the ND and manual aperture combinations. You may see some interesting things on your HDTV which may not have been initially apparent, especially in underlit stations.

I hope to get some tests done today with added eccentric weight today, available time and camera permitting.

You definitely will not get same optical sharpness from any adaptor. However, the Lemac chart says that better than 850 TV lines from the chart cannot be seen by video cameras anyway so I guess that better than 850 TV lines may be an internal creation of the camera.

I have seen reference in some posts here to suggestion that for GG imaging, sharpness levels should be set softer, not sharper, which would seem to be a contradiction.

Phil.

I shot some tests today with the larger GG movement. I shot it at 1/100 sec shutter to aggravate the bads and pulled the SLR lens aperture in to f11 at one point.

There remains a fixed pattern but it is considerably reduced. It has been replaced by a random moving grain artifact more consistent with my own disk arrangement. There were some distinct short straight sharp lines in all directions intermittantly here and there.

I think this may have been an artifact generated by the LCD HDTV I viewed it on when it was confronted by the moving grain in the more extreme examples I provoked with hostile aperture settings.

In a careful setup (although handheld), at SLR aperture f4, relay aperture f3.5, XL2 on 1/100th sec shutter, -3db gain, 25P, 16:9, with natural bright outdoors lighting from behind in a car yard at about 3-30pm late springtime Lat 32 degrees south, the image is quite pleasing with good colours, fair contrast, no visible artifacts and a less shallow workable depth of field.

Against the light it doesn't look too good at all.

as someone who has never made an adaptor...looking inside my letus. the GG has two sides to it. One smooth and one coarse. The slr image goes onto the smooth part and the camera focuses on the coarse part...correct?

edit: it's more gloss and matte rather than smooth and coarse

There was a bit of a friendly contention some time back as to which way the GG should be fitted.

I don't think any way has an overwhelming advantage. It is more commonplace for the shiny side to face the front.

The image projected by the SLR lens passes through the thickness of the groundglass to then become displayed on the rear groundglass surface.

From recollection, I think Quyen's arrangement is groundglass surface to the front but I am now very vague as to my recollection. There may be little purpose to reversing the groundglass to face rearwards if it does not already. This will throw your SLR lens backfocus adjustments out by the thickness of the groundglass if you attempt it.

damn...i was hoping this was going to be my solution!!

Am on the verge of giving up. Under every different combination of variables that "film" of grain is clearly visible...there is no way I can use it like it is

Phil.

Might as well give it best for the moment until some more R & D is in.

I think there are solutions. One likely contender is increasing the movment (excursion) of the GG which I am examining and am encouraged to perservere with by today's results.

Another is using a finer grade of groundglass finish or backpolishing the finish which increases brightness but also introduces the risk of a ghosting effect.

Backpolishing is also a very unpredictable dark art which can ruin a groundglass finish in about 15 seconds.

Any groundglass based image relay system is not really a run and gun proposition. I've tried to make mine such an arrangement but as portable as it is, too much time is taken optimising each setup, especially when artificial lighting is needed.

I expected it to work well out of the box. With my results there is no way I can use it commercially.

Without another adaptor to compare with hands on it's tricky but I am sure if other people were getting the same results as me every single time there would be more complaints, so there is something wrong, but I cant work out what it is.

it can't be the lens, as have tried 7 different type, prime and zooms, fast and slow. have tried overexposing, underexposing on lens, camera, different combinations of both. Wide open on slr, stopped down on slr lens...all have that same "film" of grain that looks unnatural, like I am filming through some of weird filter. I need a natural look.

Bob, from your experience, what do you consider to be the best adaptor out there, ignoring the p&s for cost reasons...should i look at getting a different one?

Am sure my letus is capable of good pics, otherwise people wouldnt buy them, but something is wrong with it and am desperate to find out what!

Phil.

I don't want to get into being judge and jury on any of the alternative products as I have not given any other than Quyen's Letus a close examination and cannot make valid comment on them.

Part of the problem in any open-source environment is distilling the truth out of folk-lore and blind enthusiasm and people riding a wave which eventually subsides.

I myself am guilty of having contributed to the collective of misinformation in relating observation that was not what it initially seemed.

I try to correct any such misinformations when I have the alternative to hand.

There is a certain amount of face saving and pride involved when someone makes a decision to buy something, then finds it falls short of their expectations. I suspect a few other people have simply gone quiet and taken the discreet ebay option.

I don't think you are alone with your current difficulties, you've shared, others may have not.

In meantime, let a few others sweat on a solution for this one and let some proof come in on the alternative products.

did you download my latest clip called newletustest?

http://homepage.mac.com/philip.bloom/FileSharing25.html

It shows off the problem quite clearly. Although some of this can be minimized in post, i would be very unhappy with handing over any rushes to anyone else looking like this...

I connected up my camera to my HDTV, opened my window and shot some stuff pointing outside, fiddling with all the controls whilst monitoring it on the 37" tv. Nothing I could do would make that grain go away. It makes static shots look slightly unreal and moving shots unnacceptable. If the grain was more like grain on a camera or film grain I would be totally ok with that, but because it's a fixed pattern that is what I cannot deal with!

By the way the glob of glue on the end of the motor is deliberate. Quyen says it is to slow the motor down, but make the vibration more wide...

Phil.

I haven't dowloaded the latest clip as the problems you describe have also been evident in the XL I have been working on and the download to here on the end of an overland copper pair landline is a but on the slow side.

I have been out most of the weekend filming (okay videographing) aircraft in flight. We have Rally Australia here and there were two aerobatics displays, some more for my "Plane Junkie" archive and did you know, the DeHavilland Tiger Moth is 75 years old?

The Royal Aero Club has a celerbration da down at Murrayfield and I went there to do some coverage of that. The groundglass comes out for the telephoto shots, a 50 - 500mm Sigma on front of a FX1. Fearsome heavy with bridge and rods support and fluid-head tripod only.

It can go to 200mm - 1000mm with a doubler but for ground-to-air shots it becomes pretty much uncontrollable as you can't go wide enough to re-aquire the aircraft if it gets out of the frame.

I gathered that speed control was what the glue drop was for, air resistance governor of sorts.

My next move is to reposition the motor. In theory, this should not have an effect. Because of the parallel relationship between the eccentric weght on the GG support panel there will not be added leverage.

But I am assuming that there may be some lost motion due to flexing which repositioning the motor may eliminate.

If that does not work, then some more soldering wire goes onto the eccentric weight.

sounds great Bob, isn't it like early a.m. where you are?

Am going to get my hands on a Redrock m2 in about a week so am eager to see what it is capable of and compare!

Phil.

When you shoot some Redrock footage, be sure to post a sample of that. About 15mb is max for my computer before it starts chasing its tail.

I'd be interested in seeing how it handles overlit highlights in the out-of-focus area and daylight bounce directly towards camera off things like red brick paths and tabletops.

Yes, it's early am. Been hypotising myself watching the airshow camera tapes after a day at the dayjob then a call by the Letus owners office to shoot another test on the XL2 there.

I will Bob,

Will shoot the same set up on both the Letus and the M2 for comparison. Not sure how they compare with light loss so there might be some difference at exactly the same settings. At least the one thing i do know is I won't get the static grain on the M2 due to it being rotating disc, am I correct?

I will resize videos to a more manageable size for you too.

Phil.

You may recall a recent link posted by Chris Hurd here not long ago which referred people to archived discussion on the ancestor of M2, - Micro35, I think?

My recollection is they were also intending to go the orbiting GG route, but with small throw half-cranks and miniature ballbearing sets.

This method, when carefully set up, is much smaller than a CD-R sized disk design and just as effective. It requires a lot more metal precision engineering which should be inherently more stable.

Once backfocus and alignments are adjusted and locked, it should be less likely go anyplace without user permission.

My understanding is that these final adjustments are an awkward but once only task.

Quyen has seen my footage and can't see my film of grain! I know I am not going mad as it's cleary there, though much harder to see on a computer monitor...I just need to know if it's faulty or not. If it is then I need to get it fixed if it isn't and that's the sort of quality you will get from it then I just won't be able to use it. There is no way I can cut in non Letus footage with Letus footage unless they are both Magic Bulleted to within an inch of their lives!!!

Phil:

1. Have you looked at this outfit from your neck of the woods ?:

http://www.sgpro.co.uk/pages/home/homeframeset.html


2. I have a computer monitor I use to display my HDV footage from my FX1. I am displaying using the windows media player or VLC, or QT, depending on the file. The monitor is a Dell 21 in wide screen, 1680 by 1020 or something. If I get right up on the screen, I notice this background grain pattern. I have written off to the screen re:sampling or whatever it is. Is it possible that is what is going on with your display ?

Hi Chris

I know of Wayne Kinney's SGPro, but never tried it. I really should go down there and check it out, it's only an hour from me (a long way in English terms, next door in US terms!)

It's not the monitor as have played it through 2 HDTV, one 37" the other 26", one broadcast monitor and two different computers and it's always there.

It's definately the grain of the GG that I am seeing, you can clearly see that it is isn't vibrating enough when you switch the motor on from still, it's more blurring them slightly than making them invisible.

Having not seen any other adaptors or seen any other clean full hi def Letus vision it's hard for me to judge whether it's a problem with my particular adaptor or a failing of the technology...

I would love someone to upload a few seconds of full res letus footage untouched for me to see!!! anyone?

I actually order the book on building your own Micro35 project, that included one of the spinning disks. I think that is what Redrock is based on. I've never tried to build it though, but that might be a good project this Winter.

I actually have messed around with PVC pipe static adapters to try to learn the issues. My best result so far has been using, of all things, the plastic bags we use to put produce in at the grocery store. It is static, and shows any wrinkles and or dirt or mark, and that is the reason for spinners and vibrating screens.

However, this testing has given me a lot of insight into the issues. On of the problems I see with the FX1 is the need to get the right achromat setup so you can close focus. In that realm, what is provided by Letus to resolve that issue ?

Edit: Phil check out the forum on the SGPro site. They may have some footage now.

It's definately the grain of the GG that I am seeing, you can clearly see that it is isn't vibrating enough when you switch the motor on from still, it's more blurring them slightly than making them invisible.

Having not seen any other adaptors or seen any other clean full hi def Letus vision it's hard for me to judge whether it's a problem with my particular adaptor or a failing of the technology...



I checked it out now that I am home for lunch, and can look at it on that monitor. Yeah, I see the grain. Also see a couple of blotches as I look at the footage in loop. One shows up at top of pilar, emerging from the red, the other just by her right cheek.

So what side is the GG on ? In my opinion, it should be on the side of you camera. The ground glass is what the image forms on. It seems to me the immage would be degraded shoot throught the clear glass.

yeah there are a couple of blotches...just a couple of specks of dust somewhere inside. I'm guessing probably on the macro (it's not a true achromat in the Letus although that shouldn't affect the grain) maybe...tough to make it completely clean, it doesn't seem at all dust proof.

Am glad you can see the grain and it's not just me. The ground side does face the camera. What do you mean by right achromat for close focus?

If all goes to plan I will get to play with a Redrock tomorrow, am very curious to see the difference, as it rotates I won't get the same static grain effect, more swirls I guess if I am too stopped down...

Is there any GG upgrade available that would fit a Letus I wonder, that might help...I also get my A1 back from repair soon so I can try that out again and maybe even remove the macro as it doesn't need it and see how it fairs with that

I've just been fooling around with a combination of old 35mm close up lenses, and have a lot of issues with focus falling off on edges. But I understand a "proper" achromat for these purposes and to avoid chromatic aberation is a two element unit. And even with the combination of close up lenses, the image I focus on still vignettes at the edges. So I would expect the problems I am facing in my little experiments. I was just wondering what the Letus provides to gives you the improve the FX1's close focus ability.

chromatic aberation is something completely different from what I am experiencing though...am sure a proper achromat would be better. I don't have any problem get a sharp focus though.

chromatic aberation is something completely different from what I am experiencing though...am sure a proper achromat would be better. I don't have any problem get a sharp focus though.

Just saw your post in another thread. I must didn't pay much attention if you mentioned it here, but I see that there is the added element of the flip.
I had seen a lot better Letus stuff before, and was surprised at you issues. But I have seen much on the flip yet. I can see potentional for problems there too.

i gather the flip will lose me more light, but I didn't think it would affect the grain...

Saw this from Greg Bates in another thread..

The Letus flip was great until I got my HVX, at 720p you can see every bit of grain on the gg as it just does not vibrate enough to disperse the grain. The Brevis is very well put together and polished as a product. I'm waiting on the filp module now...Dennis:) I wish Quyen would upgrade the glass as my Letus Flip is collecting dust.

Do you think upgrading glass could help?

i gather the flip will lose me more light, but I didn't think it would affect the grain...

Saw this from Greg Bates in another thread..

The Letus flip was great until I got my HVX, at 720p you can see every bit of grain on the gg as it just does not vibrate enough to disperse the grain. The Brevis is very well put together and polished as a product. I'm waiting on the filp module now...Dennis:) I wish Quyen would upgrade the glass as my Letus Flip is collecting dust.

Do you think upgrading glass could help?

Wow. Thats right on point. Pretty definitive about the issue.

All of these systems were developed initially for SD, and it stands to reason grain might be a bigger issue with HD and HDV. I assume the flip is accomplished by mirror, and for some reason the grain might be being enhanced.

I saw that Brevis Cinevate site, and the demos there look great too:

http://www.cinevate.com/index.php?page=products

Yeah, both Brevis and Redrock do an HD imaging bundle...be interesting to see a "shootout" between these two.

got my M2 today. It's an astonishing piece of kit. Very well made, and in the flight case more professional than Professor Professional, head of professional studies at the University of Professionalism in the town of Professionalberg located in the state of West Professional.

Initial observations compared to my Letus Flip (I must point out there is still a possibility my flip is faulty but as I have had no success in proving or disproving this and after talking to other people with similar problems it may just be the design of the adaptor, in particular the GG and the motor...) IT IS TERRIFIC. Beautiful, crisp, sharp images. NO GRAIN...if I stop right down, and I mean right down you can see the circular lines of the GG in the sky, that's it. Yes it is upside down but with the magnet trick it's fine (although I now cannot use my viewfinder, just lots of using my expanded focus). But the image quality is about 100 times better as far as I can see. I can easily mix these images in with non adaptor stuff no problem.

I am hoping to get my hands on a Brevis in the next week. When I do I will do a direct comparison of all three.

By the way I ordered my Redrock on Monday, received it in London on Friday. Now that is fast!

Phil

Have done some mods on a LetusXL Flip to hopefully deal with the "film of grain issue".

Mods are :-

CD player tracker motor, smaller one, not the mabuchi style motor.

Eccentric weight, 18mm diameter, 2mm thick, 0.7mm countersink on centre hole to allow clearance for set back onto shaft over where the bearing in the motor case sticks out.

The weight is styled after a 180degree shutter, ie., a half-circle. A short section of the black plastic worm drive (screwjack) for the tracker is retained on the motor shaft to mount the eccentric weight on. It is too hard to get a right-size fit on the shaft otherwise

The largest (centre) of the three holes on the side of the groundglass carrier where the original motor is mounted is widened equally to allow a snug fit of the tracker motor which has to be glued in.

There is not enough space front to back for the motor to fit in between the front and the rear and about 2mm has to be trimmed from the end of the shaft with a small cutoff wheel on a Dremel. The motor is glued into the carrier.

The soldering contacts on back of the motor actually have to straddle the lip on the front section which the pillars are mounted into.

The eccentric weight operates behind the groundglass carrier, not in front of it like the standard setup with the smaller motor.

If there is too much clearance, then the weight on the motor shaft will touch the rim of the condenser lens at the rear of the groundglass enclosure tube.

The shaft itself whilst not touching anything will touch the condenser rim once the orbiting motion commences which is why it has to be trimmed.

The dropping resister on the original smaller motor is not used.

The groundglass excursion at approx 3000rpm is about 1.5mm and circular. When starting and stopping, the outer rim of the carrier will make contact with the tube enclosure however this is momentary.

The rubber ends on the front ends of the pillars need to be secured with contact cement. (Quick Grip) to prevent them from working their way out of their holes.

The noise level in operation is louder and an on-camera mike is not an option.

The test clip at the address below has been shot on a Canon XL1 in a manner to provoke the worst performance. 1/400 sec shutter to start with. An artifact will be seen in the sky. Captions on the clip tell the rest. At the end of the clip is a Lemac test chart.

The clip is a m2v file which should play on Power DVD. It is a large file.

http://www.filefactory.com/file/4b0bf1/


The mods are not for the faint hearted and fine engineeering skills are required.

FOOTNOTE: Filefactory has rejected the file for some reason.

I will load up a Divx file but the res on this is not so good.

Divx file is here :-

http://www.filefactory.com/file/fe57fd

FURTHUR FOOTNOTE: This one doesn't work either so there it goes.

I'll give it time for things to change. Maybe it takes a while for the files to be checked or something.

The mods are not for the faint hearted
Hmm. Maybe I shouldn't attempt this then. I turn pale and blackout at the sight of trimmed plastic :)

The biggest hurdle is extracting the original small motor without damaging it as the adhesive has to be carefully trimmed away, then the connections unsoldered. I wanted to be able to reinstall it.

As for the rest of the task, a small keyhole file is about all that is needed to reshape the larger hole of the three on the carrier. The larger motor has two flats pressed on the case.

The eccentric has to be turned up as a complete 18mm diameter disk on a lathe, then the waste half less the centre hub cut away in four hacksaw trims then filed to a tidy finish.

Beyond that, provided no damage is done, the original arrangment can be restored. However, ability to work to fine detail and not damage things is required.

I'm not entirely satisfied the fixed pattern has completely gone. I am also beginning to suspect that the mpeg2 codec may have some sort of memory effect on low contrast soft objects it finds in an open clear area of image. On a pan across sky, these might endure across several GOP groups.

I have seen something similar with my own device and that is a full CD-R disk size GG. Distant trees across a valley in a slightly darker triangle of side gulley momentarily did not move when I panned across them, then they jumped into place.

On the .avi file I have only seen artifacts in the sky areas in the 1/400th sec shutter footage. In the m2v file, on playback, there is a fine fixed pattern on the test chart at slower shutter speed.

Because this test was shot on MiniDV SD, there should not be any mpeg2 artifacts but they are there in the mpeg2 exported for web posting.

The truth will out as to the original camera footage when I get to see it on a HD monitor next week.

With the increased movement, things like specks of dust on the GG are no longer a problem.

The files uploaded to File Factory are in the index but when I try to access them by the links here, they are not available for download. If anyone has any ideas on how to set them free, it would be appreciated.

This is the message in red letters I get :-

"Sorry, this file is no longer available. It may have been deleted by the uploader, or has expired." - Yet the files are still there in the index.

FOOTNOTE:

File factory must have a problem or my computer does because now, the upload screen simply does not come on when selected.

The clips referred to in the post above have now been fixedso can be accessed.

The one titled "sequence01" is about a 40mb file and best represented the image quality. The divx file goes soft where the artifacts are present and is sharperwhere the image is best.

An addendum to a post I made some time back about the assembly within the Letus35 XL flip front tube enclosure.

In my wisdom or lack of it, I incorrectly referred to the groundglass screen being groundglass surface to front and motor to top left.

I had forgotten that in initially working on this specimen,I had mounted it in a soft vice for re-assembly, upside down and front to back as I was adding screws to the joints and drilling and tapping the screwholes.

The device had been at one stage in three pieces before I brought it home to fix it and I had to refer to Quyen's website to find an illustration of its correct re-assembly.

----One of many reasons why little heed should be paid to my ramblings.

Bob...you are a genius. Unfortuantely I am not!

Can I send you my Letus, will pay you £100 plus parts and shipping!!!

Love to know how you got on with the HD monitor!

Phil.

It is early days yet.The jury will be still out until I can get my hands on the XLH1 to look for bads in HDV format. That won't happen before tomorow.

I don't know about genius. It is one thing to find an orphan oddsized motor in the ice cream carton and fit it. It is another to source new motors of the same type.

This could well be why Quyen uses the small vibrator motor - availability. You can get anything you like it seems from OEM manufacturers, then comes the tricky question - how many sea-container loads? - You reply "Errr, no container, only just fourteen off plus a spare", then wait for the horse laugh.

So you have to find a middleman or a production run on an obselete mass-produced product coming to a close, then see where their surplus stock has gone.

Quyen also seems to have kept his options open in the design with three different sized holes in the motor mount area of the groundglass carrier, a large one in centre, a smaller one to one side of centre and a smaller one to the other which is the current location of the small motor.

I'll keep you informed as to the XLH1 tests.

I didn't get to shoot a test on the XLH1 as it is otherwise gainfully employed however I did shoot some more SD on the XL2 and looked at it on a high resolution production monitor.

Whilst the soft freckles from the GG are well gone, a background fainter "film-of-grain" fixed pattern artifact remains. Some more testing yet to be done to eliminate the GG as the cause.

I just wanna say u guys r truly doing folks like me a great service for sharing the problems. I'm looking at the M2 for my FX1 too. The Brevis is something new which I can consider for the same price point. Hope to see the comparison in the light loss department especially... THANKS!

A few of the dvx'ers did some work with a Brevis beta (http://www.dvxuser.com/V6/showthread.php?t=68822&highlight=brevis) and the M2 (http://www.dvxuser.com/V6/showthread.php?t=70422&page=3&highlight=brevis)...clips are not active any longer, however I should have these somewhere.

Some furthur testing with the larger motor and weight.

There remains to a lesser degree a fixed pattern artifact. When I stepped the shutter speed up to strobe the groundglass, the orbital pattern has remained elliptoid and remains canted to the left slightly as was the original smaller excursion.

In an earlier post, I had referred to the excursion having become more circular with the extra horsepower and weight. Of course it was, because I had viewed the television set as a strobe and invalidated my research by holding the appliance upright so the light from the CRT would fall on it.

Given the motion remains elliptiod I am convinced the fixed pattern is related to the much slower surface motion which occurs at the end points of the elliptoid excursion.

I am furthur encouraged in this direction by subsequent tests I did with the groundglass removed to see if the optical path alone was generating the fixed pattern. I could not observe any fixed artifacts on the high resolution monitor. This is not to say there aren't any but I could not find them.

Two possible solutions come to mind.

One is to over-drive the excursion with a heavier weight, then limit it to a circular motion by adding fixed pillars to the front of the case which supports the existing moving pillars. On the fixed pillars would rest sleeves which have a very wide clearance both in the groundglass carrier and the pillars.

This method is used for locating and driving caterpillar tracks in a hostile no lube environment. Because of the excessive clearance, the motion is converted to a rolling motion across frictional surfaces rather than a rubbing motion.

The downside is that the motion would become noisier. Think bulldozer or army tank in high speed miniature and you may get the picture. With insulation around the front tube, I think it could be resolved.

At high speeds there likely will be all manner of harmonics and random motions as well as the truly circular ones. There is some randomness in the existing Letus movment which may be why I have been able with some lenses to push to f22 with none other than the fixed pattern artifact turning up.

Another solution might be to add some tension springs to counter the gravity loading and restore the circular motion. These will also serve to maintain added positive retention of the pillars in the front cover.

This has not emerged to become a problem I thought it would with the more violent excursion I have been experimenting with.

i would love it to all work beautifully. the letus fe has the potential to be a cracking adaptor. Just that film of grain and a proper solid nikon mount would be great. hated the flimsy one. the one of the m2 is so solid

I'll be taking a four week break from any experimentation with improving the Letus35 for HD as I have a demo scene to organise and shoot this coming month plus earn the daily bread.

My imaginings of promoting a more circular orbit of the GG is to start with two fine coil springs of about 1/8" diameter such as you find in old copiers, printers or Lexmark Optra S1250 toner cartridges.

The attach points on the groundglass carrier would be midway on each side. The anchor points would be to pins in radius holes bridging the upper cutout space on each side of the upper pillar in the front (base) which holds the base of the pillars.

This method may provoke a "figure of eight" motion of the groundglass which would require more countermass below the motor on the groundglass carrier to counteract.

"Figure of eight" would create an almost stationary spot somewhere on the groundglass which would appear as a very evident patch of fixed pattern.