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Old April 13th, 2008, 04:32 PM   #1
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New LetusExtreme Owner -- with questions

I took delivery of my LetusExtreme a week ago. I've got an XH-A1 to which I have attached it. While I await the arrival of a 28mm and a 85mm lens, I've been using a Canon FD 200mm f/4 and a Canon FD 50mm f/1.4. I've gotten what I believe to be some great images. However, I'm feeling kind of stupid about a few things:

1. I was never able to actually get my A1 to focus in on the grain in the ground glass -- neither manually or with the auto focus. To me, it just looked like a creamy white blur -- no discernible grain per se. So, rather than "marking" a focus point, I just set my A1 to normal auto focus (not the "instant" auto focus which has a sensor external to the lens). I zoom in as desired on the ground glass. Then I manually focus my 35mm lens. If I deem it necessary, I can make minor focus adjustments with the manual focus ring on the A1. But, I confess I haven't had to do that very much. The auto focus seems to do just fine, unless it's a low-light, low contrast situation.

So, my question: am I missing something here? Why do you suppose I can't seem to see any discernible grain in the ground glass? (btw, yes, the motor is OFF when I'm trying to do it!) And even if I did see the grain and was able to preset a focus point (on the A1 it's easy with its set focus feature), why should I care if the auto focus seems to be working just fine?

2. Here is a link ( http://www.mediafire.com/imageview.p...dfjozz&thumb=4 )to a shot of my ground glass with the A1 zoomed out full. Notice that the glass is offset to the right and also tilted down on the right side. How do I go about adjusting to remedy this problem? Especially the slight angling of the glass.

I'm sure I'll have more questions as I go along. I look forward to being able to pick the brains of the experienced people here.

Also, here is a link to some shaky test footage ( http://www.vimeo.com/895932 ) from my first week of experimentation. One thing I concluded already is that my old tripod head is simply not good enough for smooth pans/tilts with the whole A1/Letus/lens/rails rig sitting on it. I've ordered a new, better tripod head (Bogen 516) which will be delivered next week.

Last edited by Will Schryver; April 14th, 2008 at 01:34 AM. Reason: Switched to Vimeo link
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Old April 13th, 2008, 07:00 PM   #2
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Will, the grain of the ground glass typically isn't noticeable when you have a lens attached and it's wide open. Try removing the lens or stopping down the lens to something like f8--then, I guarantee you'll be seeing some grain.

I'm not familiar with the construction of the Letus but I'm sure there's a way to adjust the alignment of the adapter with the camera.

Autofocus works fine for me too. I'm Brevis + Sony FX1. Go figure.
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Old April 13th, 2008, 07:34 PM   #3
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Autofocus is fine and I routinely use it myself.

It may be prudent to lock it off by switching to manual for individual shots to avoid it hunting on through the groundglass if you encounter a bright pinpoint in the groundglass image.

When using autofocus, set it with groundglass off, camcorder iris wide and SLR lens iris narrow as per instructions.

Then with lens apertures normal, give it a second try with the groundglass running and a sharply focussed image on the groundglass. It is possible sometimes to pick up a trace more sharpness but not always. Only a good large monitor tells the truth.
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Old April 13th, 2008, 11:37 PM   #4
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Quote:
Originally Posted by Ben Winter View Post
Will, the grain of the ground glass typically isn't noticeable when you have a lens attached and it's wide open. Try removing the lens or stopping down the lens to something like f8--then, I guarantee you'll be seeing some grain.

I'm not familiar with the construction of the Letus but I'm sure there's a way to adjust the alignment of the adapter with the camera.

Autofocus works fine for me too. I'm Brevis + Sony FX1. Go figure.
Thanks for the reply.

I followed all the instructions carefully -- I was checking for the grain with no lens attached/very bright background/zoomed in/etc. Maybe I'm expecting something more pronounced than what I see ... I'm not sure.

I guess the bottom line is that others of you are using 35mm adapters in conjunction with the camera's "through the lens" auto focus. Until I see a good reason not to, I'll continue to use it, too. Maybe once I transition to an external monitor I'll begin to notice shortcomings, but for now I'm content with how well the auto focus is working.

As far as the ground glass position is concerned, I carefully removed the cover and examined it -- it seems to be just slightly "out of square/lower right corner lower than lower left" in the same way I see it when I zoom out fully. But there's no apparent way to adjust it. I'm hoping a support e-mail to Letus will answer the question.

Thanks again for your help.
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Old April 14th, 2008, 08:44 AM   #5
 
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Will...

I see exactly the same thing on my LEX with an EX1. Vignetting unequally in the four corners, worst in the lower left. I emailed Letus Custmer Support and was told that the GG screen is significantly biggert than a 35mm image area and that the uneven vignetting would disappear when I installed a lens. In my case, the vignetting is caused by the Canon FD lens mount clear aperture being small enough to vignette on the corners of the GG.

It is true that the installation of a Canon lens mitigates the vignetting. I need to zoom anywhere from 77% to 100% to totally eliminate the vignetting from my captured image. It would seem I would have to zoom less if the image was properly centered on the camera sensor, but, there is no adjustment for axis position.
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Old April 30th, 2008, 07:11 PM   #6
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My Letus arrives on Friday . . .

I have the same lens package you do and wonder if I would be better served to change to a different lens to make the system work better.

Is there a better lens (ie. Nikon, Zeiss etc)

Thank you.
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Old May 1st, 2008, 07:46 PM   #7
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I'm not sure if the Canon has a peaking feature as I have a Sony V1u, but if you engage it when you try and focus manually on the ground glass, the red (or whatever color your peaking is) will stick right out! It really helps in focusing on the ground glass.
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Old May 12th, 2008, 08:00 AM   #8
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EX1 FD Letus

I also run an EX1 with a Letus and FD mounted lenses.

And I also am slightly frustrated by the vignetting. The bare-minimum Zoom number on my EX1 I find is 73 but there is still slight vertical-bar vignetting up both sides and at the corners, especially the left. And so too is my image very much to the right.

When attaching my 28mm FD lens, compared to when it is mounted on my Canon T90 SLR, I find I lose about 10-15mm of my original 35mm frame, thus making the 28mm into something more like a 32-38mm. This is the same with all lenses. A little annoying but something I can live with. (This is at Z73 or more)

One major aid when using the Letus was to turn off the steadycam function on the EX1. You must do this! Otherwise vignetting will be wildly all-over-the-place.

I also find the mounting of the Letus to be a bit of a fine art. And am still unsure if the whole process is worth the money, hastle, added weight and size....
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Old May 12th, 2008, 02:18 PM   #9
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Since my original question/complaint, I have come to understand that the GG on the Letus is considerably larger than traditional "Academy" frame size. I have a considerable amount of zoom capacity left after zooming inside the available frame. In fact, I sometimes zoom in further to achieve a "telephoto" view of the frame.

At this point, I am more than satisfied with what the Letus does for me. In fact, with the exception of low-light situations (like a live music performance I recorded over the weekend) I am finding it hard to ever want to remove the Letus from my XH-A1. It's the greatest thing since 24f.
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