Letus GG alignment - well to the right. Faulty?

[Stuart Boreham]

Hi,

Just got my new Letus and whoooah! - the screen appears well to the right in my viewfinder. I have to zoom in hugely to loose the vignetting so all my wide lenses stop being wide angles- I loose half the coverage. Grrrr.

This is really annoying. As far as I can see its way beyond anything other people have been faced with. Do I have a problem?( I am sure I do actually but what I mean is - is my Letus broken?)

Have attached a picture to show you but not sure how to get it to display properly- maybe some kindly soul will assist.

Cheers

S

[Stuart Boreham]

PS Yes- I know I have no zoomed in enough in the picture - I zoomed out to show how great the offset was on the whole screen :-)

[Rob Collins]

I just got mine and it's similar. You need to be zoomed on the EX1 to around 73, which from what I've heard is pretty standard.

[Stuart Boreham]

Phil Bloom is saying 77. But why on earth can't they get the screen to appearin the middle of the light pathway? I would have through it was pretty much an essential part of the accuracy needed to manufacture such an item.

I am well disappointed - its like using a 35mm stills lens on a small chip digi SLR camera- there is a 1.5X or so focal length multiplication factorand it sucks - all your wides become less wide.

S

[Brandon Freeman]

Well, to be fair, the ground glass is MUCH larger than a 35mm frame. So, to get "true" movie 35mm, you're going to have to zoom in that far anyway. At least that's what I've read from a number of sources.

[Stuart Boreham]

It can't be that much bigger or you'd get significant fall off as you get to the edge of the image circle of the lens. I'mm maybe try it with some DX lenses- ones designed for the small digi sensor on still cameras - and see what happens.

S

[Bob Hart]

Stuart.

The recoverable image area from the groundglass is more than large enough to replicate the 35mm motion picture frame which is what these groundglass adaptors are primarily intended to do.

With the alternative adaptors to the P+S Technik products, there has been a trend towards larger groundglass areas. There is a bonus if you have good wide aperture stills lenses on front. That is, being able to frame wider on the groundglass and pick up some extra apparent resolution.

Put 35mm motion picture lenses on front and you will find you have to zoom in furthur to be rid of a corner vignette.

It would be nice to have a perfect rectangle in the centre of viewfinder frame as you zoom in. Not all cameras zoom in perfectly on centre. You may also observe with a well used Mini35 and the Sony HVR-Z1 that the image circle starts a little to the right side and walks across the frame to centre and disappears the corners almost equally as you zoom in.

With your DX lenses, I think you may find corner fall-off at the zoom settings you are using.

On the EX1 , I have found that 42mm on the zoom-in with the Extreme is fine. Care needs to be taken in mounting the Extreme to the camera. It only takes a whisker of angular deviation off the optical centre-axis to move the frame off centre.

I think there is a little bit of offcentre to the right as your view suggests but it is well within acceptable limits for me at least. Of most importance is that the optical centrelines through the flip path remain parallel and the groundglass plane and the mount faces are also parallel. It would be prudent not to force centricity of the groundglass frame to camcorder frame just for the sake of tidyness because you may then introduce uneven camcorder focus across the groundglass area.

[Bob Hart]

Message deleted - double post

[Bob Hart]

Message deleted - edit seems to have developed a bug.

[Stuart Boreham]

Thanks Bob- I agree especailly about forcing the alignment by angling the view of the Ex1 into the letus.

I am very irritated that the whole thing is so much out of alignemnt- the big question is 'why'? Why can't they just be manufactured so the screen is central?

Take a look at the second image attached- the entire optical path is out of alignment. The image shows the camera position in order to get the target certral in the viewfinder - its about 2 inches to the right again. Frustrating and as far as I can see unnecessary if it was properly built...

S

[Bob Hart]

Stuart.


I cant speak for the Le brothers for they alone know what is inside the Extreme and what qualities went into their design and subsequent build. I have not gone inside and won't do so until something breaks.

I know from my own adaptor that setting a flip path up is heaps more difficult than setting up two simple optical centres on opposite sides of a groundglass on the wall of a box and having them coincide.

My layout is different to the Extreme and to P+S Technik's Mini35.

The Mini35 has an adjustable surface coated mirror inside to enable alignments to be tidied up, so if P+S developers, as precision camera engineers had to build alignment in, you can bet that angular error from putting prisms in metal boxes is not so easy to resolve.

Perhaps I shall draw an analogy here.

In 1976, there wasa certain popular local brand of motor car had a 6 cylinder engine which was robust, reasonably efficient and was good for about 250,000 kilometres before being moved on by the owners.

Then there was the then three times the expense upmarket car which had a six cylinder engine which was robust, quite efficient and was good for about 250,000 kilomentres before being moved on by the owners.

They look pretty much alike as rusty canoes sitting on top of others waiting for their turn at the crusher.

The upmarket car engine was a beautifully engineered piece of work and would suffer more boy racer abuse than the downmarket one before giving up. Both engines, if sensibly driven were relatively trouble-free.

The local popular engine when torn down could be found to have anything up to 1.5mm difference in the deck height from crank main bearing centres front and rear, which is really quite unacceptable from an engineering standpoint.

The average Joe or Joan who drove the local product was totally unaware and could care even less until it stopped, always from reasons other than the deck to main bearing centre anomaly.

The Letus Extreme is not a P+S Technik Mini35. However it does yield similar creative results which might otherwise be unaffordable to the ones who have bought it.

My inclination is - yes, criticise any build issues you find there and address some stern words to the brothers if you feel you should.

I have an old worn down Nikon which was said to have belonged to a photo journo who worked in SE Asia in the early to mid-seventies. True or false I don't know but I find myself pondering the many things the operator might have seen through that lens and what changes or otherwise he may have brought about in people's lives by using it. I see the same lens sitting mint and pristine in a storefront and ask myself, a great example of preservation perhaps but what was the worth of it all.

My inclination and wish would be to have the ability to take one outside and use it, a lot, wearing all the paint off the corners and burnishing the black finish off the corners of the lenses with lots of focus adjustment, flatten a lot of batteries, maybe wear out a motor or two and create beautiful and memorable work and maybe change a life or two for the better. Earning some money along the way wouldn't hurt either.

[Stuart Boreham]

You are funny :-)

s

[Bob Hart]

Stuart.


I sincerely hope I have not caused aggravation by my comments.

There likely is an off-centre situation as you indicate as I also observe it in the specimen I have as far as groundglass to image frame co-incidence goes.

Be wary though of assuming centre of the camcorder handle is centre of optical axis. It may be positioned for best mass balance.

One would imagine the tripod bolthole would be dead centre on the optical axis. I think with the PS150/PD170 it is about 8mm off to one side. I found out the hard way when building my own adaptor.

[Stuart Boreham]

No not aggro at all. English are hard to offend. I hear what you are saying - the UK suppliers are going to talk to the Letus makers this afternoon our time so maybe we will get definitive comments

s

[Stuart Boreham]

Okay, this is where we are currently at. Mitcorp (uk supplier) rang the makaers of the Letus and it appears that the Letus is correctly aligned but that the chip on the camera is not - that there is leeway in the positioning of the chip block within the image circle and that is what causes the misalignment.

Well, I have not tested the camera independantly yet but it sounds feasible enough I suppose. If that was the case then other cameras would show the Letus screen in a different positon and other Letuis on my camera would show the screen in the same position.

Looking forward to having a go at this :-)

s