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Old March 28th, 2008, 05:32 AM   #1
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Letus Extreme & EX1 question

A question about the ordering of things: since I now have my Letus and now have two lenses, two focusing rings, two apertures, etc., I want to be clear about how each is used in this setup.

EX1 Focusing ring: fixed on ground glass
EX1 aperture: variable for light control
Letus focusing ring: focus on subject
Letus aperture: depth of field control

Am I right?
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Old March 28th, 2008, 09:28 AM   #2
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And another question

I can still see the ground glass artifacts in the shot, especially in the out-of-focus regions. I think I have everything set up properly (except for the vignetting you'll see in this frame), so- is there a way to avoid this?

Look at the artifacts in the upper portion of this frame. They move with the camera and are not just funky textures in the background.
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Old March 28th, 2008, 09:42 AM   #3
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It looks like your prime lens is not wide open. In my experience shooting with any wider lens then 35mm you should always keep your lens at widest possible aperture.

Also if there is too much light in general you have to use ND in front of the prime lens (not the EX1 built in ND) to get rid of the gg grain totally. With my 24mm f2.8 I need to do this in many situations.

What lens is that? It also looks like there is some vignetting. How far are you zoomed in? I usually zoom in at around 80 or 75 depending on the prime lens.

Sami
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Old March 28th, 2008, 09:46 AM   #4
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These artifacts occur in 2 circumstances.

1: The aperture of the prime lens is to small. (Should be 2.8 or better)
2: The shutter speed on the EX1 is 1/250 or above.

From the picture it looks as it is the aperture.

I've never used an ND filter. Using Canon's 50mm F1.4 in bright sunlight and snow is not a problem.

Check out www.oyvindstokkan.no.

What lens was it shot with? Are you sure the ground glass is vibrating? The letus has some fragile solders that might come off some times.
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Old March 28th, 2008, 09:54 AM   #5
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With my Canon FD 50mm f1.4 I've never had this problem. With my 85 f1.2L I can shoot even without turning the Letus on and no grain will be visible.

With 35mm f2 and 20mm f2.8 I see the grain quite often and Im being really careful and using ND in front of the prime lens as much as I can.

Sami
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Old March 28th, 2008, 09:59 AM   #6
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Thanks, gentlemen- what you say makes sense, but that's not the problem.

I'm using a Canon FD 135mm F2.8 lens. There was very little light today- VERY heavy overcast. The apertures on the prime AND the camera were wide open. The lens is a prime, not a zoom. And the Letus was vibrating- the GG texture is DEFINITELY visible when it's not.

I can see how this effect is exaggerated on a day when there's little contrast in the scene.

I'm assuming that it's advantageous, on a bright day, to stop down the camera's lens so that the GG is as sharp as possible, correct?
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Old March 28th, 2008, 10:10 AM   #7
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Then it sounds as though a 2.8 lens is the upper limit. I'll try my 50mm f1.4 and see what other large-aperture wonders eBay holds.
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Old March 28th, 2008, 10:20 AM   #8
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Originally Posted by Steven D. Martin View Post
Then it sounds as though a 2.8 lens is the upper limit. I'll try my 50mm f1.4 and see what other large-aperture wonders eBay holds.
Im sure you wont have any problems with the 50mm lens. Let us know.
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Old March 28th, 2008, 12:35 PM   #9
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OK, another problem

I thought this was just a viewfinder artifact, but it captures to video this way. I have brown horizontal bands through my images. The attached photo is of the ground glass, motor turned off, It's there when the motor's on, plus it doesn't matter where the camera's pointed.

This is beginning to s*ck.
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Old March 28th, 2008, 12:49 PM   #10
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Hi Steven

Sorry you are having problems. But rest assured you can get good help from the forum members and if it is a problem with the Letus they are also known for their good customer service.

Im just going to ask you the obvious: do you have Image Stabilizer turned off?

And you dont see this when the adapter is detached and you shoot with EX1 only?

I dont see this in the first duck screen crab you provided, do you see it there as well?

Sami
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Old March 28th, 2008, 01:34 PM   #11
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Every piece of new, innovative gear requires a bit of a learning curve, so thanks guys, for your patience.

No, I don't have image stabilization turned off.
No, I don't see the bands when I shoot with the EX1 only.

And, I took the Letus off the camera and just looked through it a few different ways, and I never could find the bands on the GG.

I don't see the bands in the duck frame, but I saw them in another shot I did this morning. They're subtle, but there's there.

So- do you think this is a problem caused by the image stabilization?
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Old March 28th, 2008, 01:36 PM   #12
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And BTW, the GG artifacts are not present with my 50mm f1.4 lens. That solves that.
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Old March 28th, 2008, 01:44 PM   #13
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Originally Posted by Steven D. Martin View Post
So- do you think this is a problem caused by the image stabilization?
I doubt it but I would try it out definately. Try panning slowly and you can see the frame wobble as it tries to compensate for the gg vibration. IS is recommended to be kept off.

I did some shooting with the IS on today and got some cool effects though but in general it should be kept off.

sami
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Old March 28th, 2008, 04:00 PM   #14
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No, I don't have any problem with wobble. It's those brown bars across the screen- that's my concern du jour.
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Old March 28th, 2008, 04:48 PM   #15
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The EX1 is pushing the limits of adaptors more than other cameras. With the 1/2" image area, larger diameter of the camcorder lens.

The size of the path through the flip module the camera actually sees, seems to me to be closer to the edges.

The gradation of brightness top to bottom may be related to angular deflection of the whole adaptor off camcorder optical centre, possibly downwards. You may be picking up a horizontal edge even though it is not vignetting.

Whilst things screw into the filter camcorder mount and one assumes things must therefore be square, in reality, there is quite a lot of compliance in the camera case structure, enough to allow quite a bit of deflection.

With the EX1 this may be more critical as there is less broadness of the path to play with. Prism paths are strange things.

A straight edged area ofbrightness falloff occurs both when the taking lens is just short of beginning to vignette and if an edge of the prism path is beginning to come into the camcorder view.

In my rough experiments with the Mini35 I found it did not take much to bring something like this into view.

The band in the middle is another matter. Have a peek through the adaptor and look for a bit of swarf or a fingerprint on one of the prisms, or if they are surface coated, a bit of missing shiny stuff.

A dob or string of the white adhesive if Quyen is still using it, resting across a surface or hanging in the path somewhere might be enough to do it.
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