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Old June 5th, 2008, 11:11 PM   #16
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Stuart.


Furthur to above posts, the JVC camera I want to play with is in hospital with the usual firewire malady and also being firmware upgraded for the DR100, so I cannot do the homework for you until a week or more down the track.

A hint on setting backfocus which I am sure you already know but repeating anyway because I have pedantic tendencies and am simply getting old.

The Fujinon lens needs to be set at its widest aperture in order for the best focus point to be found. This means closing the aperture on the SLR lens to provoke the groundglass texture and also keep light into the camera at an acceptable level.

If the forward offset of the whole appliance forward of the camera gives best sharpness and no edge softness or distortions, then my inclination would be to make a new longer spacer ring or another threaded spacer to add length.

Don't go to any of this trouble just yet. Another solution might be found, maybe even something as simple as an achromat swap in back of the Extreme.
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Old June 6th, 2008, 02:37 AM   #17
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Bob,

Many thanks for all those thoughts. We're taking them all on board and your gesture of a test at your end is most generous. I'm extremely grateful. If I was anywhere near Perth I'd buy you large beer! (mmm, the majority of my family in law live in Perth...)

In reply to some of your points;

I don't think the 82mm thread on the Letus is specific to the JVC. I might be wrong but I'm sure the hvx200 is 82mm also. This may mean it's more of a generic adaptor!?

We will test for misalignment due to load on the rails in a minute. That's good thinking. However, to see how good the Zacuto rails were we loaded the Letus end up with everything before we put on the JVC. I have to say, hardly any movement under load. Really quite impressive. My initial thought of a stepped bridge was one of scepticism, but I can say that it's exceeded my expectations easily.

As for the focal plane point on the Letus being the rear of the Letus support; well, that's how I've always understood it too. However, when we were testing we noticed that all the distances on all the lenses were consistently out by about 10mm! We then assumed that we'd just misinterpreted the instructions so now measure from the front of the support, which now gives accurate distances. I can accept that some internal collimation error on the SLR lens can occur, but not on all 7 that we have!

Now, when my employer sent me on a camera engineering course (many moons ago) I have to admit I never really paid that much attention. (I was always more concerned with making nice pictures than how it all worked etc.. and also, can I go to the pub now please?...) so, that said could you explain what you mean by A and B blocking on the star chart. Fortunately I'm conversant with Moire so I'm Ok on that one at least!

I had a long chat with one of my partners last night and we've agreed to abandon in camera vignetting, so we'll be taking your good advice and doing it in post from now on. Like you say, salt an' all that.

Now, we also came to the conclusion that we are not under any circumstances prepared to alter, adapt or take apart the Letus in any way. If we have to do any of that to obtain a sharp image then its simply not the right product for us and is not truly fit for the purpose it was sold to do. Either it's faulty or it's simply not compatible with 'ALL' JVC GY cameras.

So with that in mind, as a business, we can not afford to risk it on jobs right now. We are due to use it next week (although I'll be hiring again now, which really makes me cross as I have one sat in my bloody office that I can't use and I'm pissing money down the drain on hire again) and again at the end of June. I think that if we get nowhere with it and are left with no option but to adapt and alter then I'll be sending it back, getting a refund and buying another product. Apart from the fact I'm simply not able on a fine engineering level I'm just not in the business of buying things and having to mess around with them so they work.

I've heard nothing but good things about this unit, which is precisely why I bought it. I just hope I can be another one to say good things about it, but right now I can't!

I'm still hoping!

I've not yet had a reply from the manufacturer other than 'what's wrong with using macro? lots of people use it'! so I'm still hoping for some more constructive advice. In the mean time I'll try to remain patient (for a few more days at least).

Stuart
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Old June 6th, 2008, 05:52 AM   #18
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Stuart.


The Lemac chart is a A4 sized cardboard chart which has 4 Siemens stars one in each corner, other markers, a contrast row and two rows of boxes made up of vertical or horizontal lines and aspect ratio guides.

The upper row of blocks as I call them are "A", "B" etc starting from sharpest which is film, "B" which is 862 lines then on to lower resolutions. The lines are upright for assessing horizontal resolution

The lower row of blocks starts at "F" which is film, the "G" etc onward to lower resolutions. The lines in these are horizontal for assessing vertical resolution.

The 10mm or so consistent error suggests lens flange to focal plane being very slightly off. To get a 10mm increment focal plane to actual subject is a mere whisker on each of the threaded adjustments I have built-in to my own home made adaptor, a movement of less than about 1/10th of 0.5mm, in kitchen terms, maybe about the thickness of clingwrap. I am no engineer, just a hack-artist which is why I had to design in the ability to adjust.

P+S Technik do a full collimation with a projection rig and install superfine metal shims where needed as is normal lens collimation practice. They are ARRI camera engineers after all. Again this is where the cost premium comes from with the MINI35.

What process is used in the Extreme I do not know. I imagine that for product consistency, they would use some sort of assembly jig to get identical placement in all examples.

As to turnkey utility out of the box, that has obviously not happened for you, understandably a real disappointment

A local here opted out of groundglass relay of all flavours for his ad work for reason that the extra time taken to manage the system to his standards and extra lighting requirements amounted to productivity lost and moved up to a F950.

Hopefully your issues will be resolved when the direct relay systems for the JVC, Sony Z7 and Canon XL family are sorted. Of course this does not help you right now.

Please let us know if you still have the unit in about a ten days time. That is about when I will be able to get at a JVC camera.

Last edited by Bob Hart; June 6th, 2008 at 05:56 AM. Reason: error
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Old June 6th, 2008, 08:19 AM   #19
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Hi Bob,

I remember the chart now. Think I might even have an old one somewhere! It'll be one of the things I took home when one of the studios I worked in closed down. I'll have a look for it. Nice to know what its true purpose is!

As for the Letus; well I spent another couple of hours trying to get things sharp this morning without success. I am 100% confident there is no problem with the JVC end, which only leaves the Letus or the 35mm lenses at fault. Given that the same soft images occur on all 7 lenses I'd wager it's the Letus.

I'll have a rest from it this weekend and it looks like we now have Tuesday free, so I'll commit the day to yet more testing. If nothing comes to light by then I'll be sending it back. I can't waste any more time or money on it. Sadly I've still not had any further reply from the manufacturer which all adds to me wanting rid of the damn thing. It seems it was not the right thing for us to have bought. What a shame as we had high expectations from it.

Stuart
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Old June 6th, 2008, 09:00 AM   #20
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Stuart,
I don't know if this will help you, but here's what I do with my canon h1 and a1. I've only had the Extreme for a couple of weeks, and had to spend some time fooling with it ,along with another camera guy who is more tech than me, and had experience with the brevis. I had a hard time seeing the ground glass, until I figured out a solution.
1-Without the slr lens yet attached, I zoom in on a lighted white wall. Even zoomed in , it's very hard to see the little black particles for getting focus. I realized that using my "magnifying" function on the Canon made it possible to see the ground glass.
2- Once I had the Canon focused in, i use the "focus preset" button to lock down a focal point. Even if I mistakenly turn the camera's focus ring, I can use the prest to go back (it's right at .9mm).
3-I hear what you're sying about the gg image being off horizontal plane. I tried adjusting, but it seems to always go back. Anyways. i zoom back out to just before vignetting, and set that point with my "zoom preset" button. This way, if i zoom in tight, i can always go back to the correct spot.
4- put on the slr lens and focus.
Hope this helps.
Bruce yarock
www.yarock.com
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Old June 10th, 2008, 02:16 AM   #21
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Well I've enjoyed a nice weekend watching England hammer New Zealand at Trent Bridge and having been away from this infuriating problem I started the day fresh with enthusiasm, hoping to get this sorted.

It got quashed quickly!

I'm fed up now. This bloody thing is useless. It's either not designed for the JVC or I've got a dud.

I'm going to try one more time. The sharpest point of focus with it is simply NOT SHARP!

So far it's been an absolute waste of my time and money, and still no reply from the manufacturer.

Anyone got any more ideas?
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Old June 10th, 2008, 09:24 AM   #22
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Stuart.


I got hold of the JVCHD100 tonight to set it up with the MINI35 for this weekend's shoot.

I put the Extreme on first.

The Fujinon needed just a touch of macro for sharpest focus.

The results off the Extreme and the MINI35 were comparable, the Mini35 slightly better on a movie sized frame off the groundglass.

I rolled some tape however was not able to capture, as the cam's fire wire seems to be dead despite having been fixed by the doctor or claimed to have been fixed. The battery went flat before I could port it across via component to the Z1 at 1080i.

If you send me an email, I'll mail you the tape.
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Old June 10th, 2008, 12:02 PM   #23
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Hi Bob,


So...maybe I'm expecting too much from the Letus then? Maybe the sharpest image I can get is as good as it gets?

You are a real star for doing a test your end. I'll send you a mail. I'd really love to see your results.

Any chance you could tell me the exact method you used to achieve sharpness (well soft sharpness).

Many thanks Bob

Stuart
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Old June 10th, 2008, 06:56 PM   #24
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Stuart.


I cannot say your particular unit is not defective. Being so far off-axis as you describe points to something if the actual mounts are straight.

No doubt you have already checked the face where the 82mm ring goes into the back of the Extreme. This should be located firm against the body all the way around with no high places.

Half a hair will put you more off-centre than it might otherwise be. This will also push you a little more off sharp focus without macro selected.

That macro thing does discomfort me a little but that is what it is there for. It is the same element within the Fujinon lens that moves as is moved by the backfocus adjustment.

There is really only one way to be assured the image is as sharp as you can get it and that is with a bigger screen to look at.

With the JVC LCD screen you can get close with the test patterns and using moire to get to the sharpest point, but out there in the real world sharp focus is a harder ask especially if you are nearsighted like me and perfectly adapted to soft images.

Sorry it has not worked for you. Your expectations may be beyond what the system can deliver for you but until I can see a comparative image between two different camera/Extreme combinations I can't make that judgement validly either.

I'll see if I can get the tape captured over the weekend.

Last edited by Bob Hart; June 10th, 2008 at 06:59 PM. Reason: error
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Old June 11th, 2008, 09:39 AM   #25
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One thing I did notice is that when you tighten the grub screws to lock the SLR lens attachment on to the front, it pushed slightly off kilter. You have to have one person pushing the adaptor against the Letus while the other slightly tightens each grub screw. Its really easy to end up with one side about a mm or 2 away from the Letus body!

I'm now wondering whether;

a: the best image I'm getting is as sharp as it gets with this unit (that was the Siemens star previously attached) and that my expectations of the Letus were just too high. I appreciate the DOF adapters give softer images to that of a HD lens for example, but, wow. Softer than I thought!

or

b: There is something slightly out of alignment within the unit giving me soft images.

The results from the tests so far look like the image is sharp but has been softened afterwards. Does that make sense? It's like a sharp image that's been gaussian blurred!

We are going to get it as best as we can and shoot with it next week. I don't know if I'm mad or not to risk this. We will aim to shoot everything without the adapter too as backup!

The only way I think I can get better test results is to get hold of a very large HD monitor, which I can't do right now. On that subject you should be able to get sharp images using normal crts. I even know that mr Phil Bloom shoots a lot of his stuff using the viewfinder only!!!!! And there's nothing wrong with his pictures, although I've never seen them on anything other than a PC.

So, this infuriating saga continues....and oh...STILL no reply from the manufacturer!
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Old June 11th, 2008, 10:48 AM   #26
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Stuart:

I've shot a couple of Letus adapters, as well a few self made on 4 different cameras (VX2000, FX1,HV20, HVX200), and every one of reacts to the achromat combo provided by the manufacturer in a different way. With a Letus35a, I had to replace their achromat, with Cinevate's to make things work. However, with the LetusFE (predecessor to the Extreme) I could mount on all 4 and be able to get a decent focus on the ground glass.

I suggest that what is happening is as you zoom in, you are losing focus capability. You may think you are still in the focus range, but you are not likely there, and this is typical. What you are trying to do is get zoomed just inside the vignetting on the image, but no more. In some instance, you have to live with slight vignetting.

You can resolve by adding tubes to extend distance between camera lens and ground glass, or changing achromats. It takes experimentation. I note that BH Photo sells several different versions of the Letus, for different cameras, because of this issue, I suspect, so have you checked with Zacuto regarding that.
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Old June 11th, 2008, 11:20 AM   #27
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Stuart,

i have downloaded the siemens star you posted. We cant objectively verify the situation you are in since this image doesnt include targets for the corners where we can also help you gauge wether what your getting is the "acceptable" image from the letus adapter.

I suggest this, if you dont have a focus chart try to print additional siemens stars (photcopy?) and mount them on the wall in a way that would fit the corners and sides of your 16x9 framing. check perpendicularity of the wall against your cam/setup, Focus as best you can then post the image, zoom and other lens settings on the fujinon and 35mm lens.

this way, most of us who has experienced working with adapters especialy those with the same setup as yours can confirm or comment on the results you are getting.

With an adapter on the hd100 i suggest to set detail to normal or -1 up to -3. min or lower detail will add to the diffusion introduced by a focusing screen.

Ted
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Old June 11th, 2008, 06:48 PM   #28
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Ted has beaten me to it. I was about to ask the same question.

There are some contentions as to sharpening detail, the groundglass texture being visible to the camera and the risk that extra detail load on the codec will cause softening due to the codec throwing it away to preserve frame rate.

I contend that in good lighting, adequate groundglass motion and correct shutter speeds, there should be actually less detail load on the codec with selective focus going on.

When it bites is where there is low light combining with tighter lenses already provoking artifacts. The added video gain noise makes the sharpness disappear dramatically.

My personal preference is to bring the detail up a little. You may have to drop it back a little with wide lenses. With wides, lots more background textural detail will be in sharper focus and the camera may want to try to sharpen it all.

Last edited by Bob Hart; June 11th, 2008 at 06:54 PM. Reason: error
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Old June 20th, 2008, 10:55 AM   #29
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Quote:
Originally Posted by Bob Hart View Post
My personal preference is to bring the detail up a little. You may have to drop it back a little with wide lenses. With wides, lots more background textural detail will be in sharper focus and the camera may want to try to sharpen it all.
What a great suggestion. The detail is set to min. Why didn't I think of that?

I've just got in from a huge unexpected short notice job filming 6 open heart operations in a hospital. So, as soon as i catch breath and sort myself out for the next shoot (which should be with the Letus) I get back to you with my next test results.

How did you get on with your test Bob?

Stuart
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Old June 20th, 2008, 10:17 PM   #30
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Stuart.


I shot some footage on the EX1 last weekend and it is posted now at www.exposureroom.com under the membership DARANGULAFILM. Any videos with Congoro in the title header was shot on it, only one minute each of slow-mo of medieval extras slugging it out with swords etc..

My relay zoom setting was about 42mm.

As for the JVC HD100, I did give it a short try but the firewire port was still burnt out and I could not capture it and had to hand the camera back for the weekend shoot. I could not copy out analogue to the Sony on 1080i. It just would not do it - blue screen only.

There was I recall a similar offset to that seen on some of the other images posted here. I was able to get 862 or better lines of sharpness on the Lemac chart.

You can gain some apparent resolution compared to the P+S when you zoom back as far as you can off the groundglass without vignetting. On the same frame size as the P+S, you lose some and the contrast off the P+S is better.

This of course is not a truthful comparative test as the P+S is direct relay and the Letus image is going through more pieces of glass via the Fujinon lens.
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