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Old May 14th, 2007, 06:08 PM   #1
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strange focus

Hi guys

How is it possible to get this focus? I have it on all other shots, except wide. Only the center of the image is sharp.

all new hd 200e, 17x5 lens

I mounted the lens on the camcorder myself and tried to adjust back focus.
I hope I did something wrong, so it is not lenses fault.

Thanks

Petr Bastar
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strange focus-right-side.jpg   strange focus-wide1.jpg  

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Old May 14th, 2007, 06:17 PM   #2
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Is this a 17x5mm HD lens? I've seen something similar testing a friend's old 1/3" fujinon designed for 4x3 coverage.

Do you have a wide angle adapter attached to the lens?

Take the lens off and make sure you don't have any "burrs" in the bayonet mount of the camera or the lens mount itself.
Then re-seat the lens and see if there is any improvement.
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Old May 15th, 2007, 03:30 AM   #3
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Hi,

Yes, this is Fujinon HD 17x5 for JVC, I have also the stock lens and it gives me the same. I removed them and attached to the camera several times and it is still the same. Is it possible to mount it wrong on the camera? Everything fits in its place, it is steady. (sorry for my english).

As you said, it gives me the effect like I had a non zoom wide convertor and zoomed in. But I dont have it.

On wide side, I dont see it.


Still dont know, what I am doing wrong.

I shot in HDV 50p, sharpness normal, shutter auto. I also used various scene files.
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Old May 15th, 2007, 04:06 AM   #4
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Hi!
I'm no expert here, but since it happens on both your lens (the 16x and the 17x), it sounds like there's something with the camera's lens mount - probably there's some miscalibration of some sort. Either that, or you are not mounting it correctly...just place the lens gently on it's place, making sure it's not tilted, and then tighten it up.
In case you are mounting the lens correctly, I would take the camera in for service immediately.
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Old May 15th, 2007, 11:36 AM   #5
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After explaining the problem to my supplier, he told me that he thinks the camera needs to be set up on a light box.

Its strange that I have read about many issues with this camera or 100/110s, but never seen this.

Had anyone this problem?
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Old May 15th, 2007, 02:22 PM   #6
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Petar,

I believe what you are experiencing happens primarily at full telephoto. You will notice the out of focus area is somewhat circular, bending around at the corners. This is a common problem with the stock lens as well as the 17x; I have not had a chance to test the 13x or the 18x; Believe me, the stock lens is much worse than the 17x in this regard.

I try not to shoot more than 40mm, where the problem is negligible. If you have to shoot something at full tele, make sure your subject matter is within the center of the frame, and whatever is near the edges is something that is not important to be in focus, or even preferred to be out of focus.

I'm not a lens expert by any means, but the outer edges of the 16x9 frame are possibly outside the designed "circle of confusion" at full tele. These lenses are designed for the 16x9, 1/3 inch chips, but it is very difficult to have perfect focus, paralax etc with the huge range of focal lengths available in one lens. I think we might be pushing the limits of the technology here at full tele. That's why the feature film folks use primes.

All cameras and lenses have their limits and sweet spots. As experts, we can achieve stunning cinematography by just working with them.

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Old May 18th, 2007, 01:59 AM   #7
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My HD200 with 17x5 lens does not exhibit this serious off center de-focus issue. Given that you've seen it with another lens, I would first suspect the lens mount not being perfectly flush, otherwise it might be an internal issue with the camera.
I would assume you'd see this while setting backfocus. Are you using a seimens chart? Images of a chart would be easier to compare, the focal length is important, and the tele end has a drop in quality with both 16x and 17x (probably less with 17x but I haven't tested them together). But the effect is more uniform...
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Old May 18th, 2007, 06:25 PM   #8
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Hi,

exactly as you said Sean. I think, it is not problem of the lens qualities when on telephoto. I adjusted the backfocus with siemens chart. When you adjust it like you want, you can get image blurred, but uniform in the whole image. I am currently dealing with JVC Pro servic centre in Germany. I can tell you nothing pleasant when you buy new "Pro" camera, lens, hdd, mic, batteries for your savings. You read about the camera all info you can and you are looking forward to it. Then you find out it is not working like it should and in the "Professional " service center they tell you, that the picture I posted above is: " slightly out of focus. This is normal."

Slightly....hmm.

I will keep you informed about the problem, the service centre will maybe look at it.
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Old May 18th, 2007, 06:38 PM   #9
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Like I mentioned in my first post, and Sean also suggested, I think you have a problem with the way the lens is seated in the mount. I suspect this because the blurry spot is not a uniform vignette shape.
Sometimes when the moving metal parts of a bayonet mount come in contact with each other you can create small aluminum "burrs" that prevent the lens from sitting flush in the mount. I would take a careful look and use a toothpick to "clean out" the mount in the camera.
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