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Old June 4th, 2008, 03:14 AM   #1
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Calling all Letus Extreme and GYHD 200 users

Does anyone use a Letus Extreme and GYHD 200 without problem?

I'm really interested to hear how other 200 users focus on the ground glass, if you can!

Apologies for a slight double post in the Letus group, but we've just received our Letus Extreme and we are not able to focus on the ground glass without using macro at full zoom. This obviously means we are unable to use the damn thing! (unless you don't mind using full zoom through all your expensive primes and experiencing awful edge distortion)

The second main issue is the image plane alignment. It's massively off centre!

I'm keen to know if this is a fault specific to the Letus Extreme unit we have just received or whether it's an indication of the JVC 200 not being the best camera for it.

Strange thing is we have hired units in the past and not really experienced this level of difficulty focusing on the ground glass although always been at the end of the focal limit.

Thanks in advance
Stuart
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Old June 4th, 2008, 08:18 AM   #2
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I know that on my HD110 the letus ex has no problem with focus, the stock lens is usually zoomed in between 20 and 30 and focus is around 5... I do not know about the lens on the 200 though... This is actually the first time i've heard of this problem... you may want to check that you are following their directions on how to focus on the GG.

and the image plane alignment is some what of an issues... I have it too, but its not "massively off center", just a bit, so I loosen the screws on the 82mm thread mount on the letus and pop the end out slightly to compensate for the difference, then tighten the screw at that angle.

by the way, you should NOT be using macro to focus... that could be your problem right there... do not use macro, the letus has a built in achromat lens which allows you to use regular lens settings, if you are using macro setting on the stock lens on your jvc, it will put everything at the extreme... So take your lens off of macro and zoom in to the center, then focus until you seen grain on the gg, and there you go.
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Old June 4th, 2008, 08:52 AM   #3
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Hi Giuseppe,

I'm afraid we follow the instructions to the letter, and always have done with other Letus units on hire. with this one you zoom all the way in, see the grain, but can't focus on it. The only way to focus on it is to use macro!!! which is obviously a no go!

So, do I have a duff anchromat within the Letus?

We've done some testing this morning to see how we can find focus on this damn thing and the only way is to have the lens at around 22mm, focus at infinity and macro somewhere around half way. Its ridiculous and not a situation I could ever allow on a job. far too fragile and Heath Robinson when you are charging clients large sums of money.

Is the stock lens on the 110 the same 16x5.5? If so then that proves that not all Letus units are the same surely. I'd allow for minor discrepancies but that much of a difference is not acceptable.
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Old June 4th, 2008, 09:08 AM   #4
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Ok, the zoom settings should be no further than say 30mm so 22mm should be fine, you might actually want to zoom in a slight bit more... the focus should be set at around 6feet (between the 5 and 7 mark) and macro off... if all of that is set you should be able to focus on the gg sharp...

I think your problem could be your Back Focus... this could throw everything out of whack... Get your simions star out and setup and make sure your back focus is correct and working properly... if your back focus is set right and its still not working, It could be a problem with the achromat, but thats highly unlikely...

try to zoom only as far as 30mm on your lens, then focus on the GG by using your flip out lcd... that should help you see the grain on the GG without having to zoom all the way in first... see if that works.
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Old June 4th, 2008, 12:44 PM   #5
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The 16X fujinon is the same for all JVC's- 110,200,250 etc.
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Old June 6th, 2008, 02:41 AM   #6
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Thanks,

I thought the JVC lenses were all the same.

I'm wondering then, why a lot of people with the same camera and Letus unti all find focus at massively different points??? Variations in Fujinon lenses or Letus achromats?

Stuart
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