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Old October 11th, 2004, 07:13 PM   #1171
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Bob,
Very possible that I don't have the SLR mount exactly aligned with the dv lens. I'll get that right on my new housing.

I'm trying to talk Les out of one of his oscillators. I'm putting together a low-cost micro35 kit for those guys who don't want to build them for themselves.

I did all the machining my self. The diopter is a dual element. Half of the coupler around the dvx lens is filled by diopter. It's a Hoya. I've got a call into century optics about getting one or two of theirs. My feeling is that's what's causing the halos.

I'll have some new footage and caps this weekend using the setup above.

Thanks for the input Bob!
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Old October 12th, 2004, 01:03 AM   #1172
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James.

If the Hoya is dual element then there probably should be no rainbows or edge softness.

I would be inclined to give it another chance.

When I set up the telescope eyepiece adaptor I found that the exact positioning of it relative to the groundglass was quite critical even though I could get sharp focus with the camcorder focus adjustments over a range of distances.

Because I machined up the new enclosure for the lens set I was able to play around with the distance between the camcorder lens front element and the diopter rear element. I found close was better for the vignetting problem I had with the internal 44mm diameter I was stuck with on the lens set. You don't have the same options with a factory diopter but you also don't need it as you don't seem to have a vignetting problem.

The telescope eyepiece front element sits only 12mm to 18mm off the groundglass so the magnification is a bit savage. A lower power magnification such as yours will have a wider permissable depth of focus but the ideal camcorder to groundglass distance may be just as critical, though probably less difficult to set up. With your rod mounting arrangement finding that best distance will be a lot easier than messing around with toilet roll centers and gaffer tape as I did.

Brett Erskine created a 4:3 24mm x 18mm image target for printing on inkjet color however I ended up using a standard barcode which gave me more contrast and used Brett's for the finer adjustments. Brett's target has a grid pattern of squares at millimetre intervals

I found furthur away than ideal or closer than ideal caused either a barrel distortion (( II )) or a pincushion distortion )) II ((. Both gave me color errors at the edges.

The final arrangement for my setup was a bit of a compromise in that I had to settle for losing about a millimetre off the 4:3 frame edge in order to get a true image. I went this course because on the PD150 it gave me a very close couple to the camcorder body which facilitated unsupported handholding with lightweight SLR lenses.

7+ gives me a nicer image but the adaptor has to sit off furthur outboard which pretty much negates handheld shots.

For the prism erector version I ordered a Century Optics 7+ achromatic diopter and first rough tests conferred a rainbow free image. The earlier proving images through a stack of three Hoyas to get 7+ was muddy and rainbowed at the corners.

7+ is about as powerful as you need to be for an erecting version through prisms as they shorten the distance from camcorder front to grounglass plane. If you are eventually going for an erecting version, you won't want more than 7+ as the prism path won't fit inside that distance.
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Old October 12th, 2004, 11:52 AM   #1173
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The prisms are next. Any recommedations?

I remember seeing Brett's directions on setting up the frame. I need to dig through the posts to find that link

Thanks again for the input Bob. I'm not going to stop this time until the adapter is finished! Look out PS!
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Old October 13th, 2004, 06:42 AM   #1174
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James.

Re: Prisms. I'm using two 40mm x 40mm x 56mm prisms which are also 40mm thick across all faces. These are a sort of standard commonly stocked size. Anything else is going to be expensive if it has to be custom made. There is wasted area of about 8mm on each down one edge but this also allows for some misalignment.

In matching up the prisms themselves, I found it impossible to design a simple method of mounting and alignment which was in the league of 5mm construction error the non-erecting Agus35 layout will tolerate and still work.

So far I am examining fusing two prisms together at the hypotenuse faces to take care of the most difficult alignment errors, that of parallel axes and exact 90 degree opposition and to eliminate one generation of internal reflection.

There is a Loctite product No 358 which is a clear bond which is set off by ultraviolet light. You don't have a problem of glue setting until you are ready for it to set.

With the prisms unitised, the mounting whilst a little more awkward initially because of the odd combined shape, will lend itself to more unskilled construction providing adjustment can be built in and the prisms can be protected from mechanical damage.

For initial mounting I am examining using several blunt-ended brass screws to hold the arrangement in place and adjust alignment of the composite prism array in the plastic tube.

Once that is set correctly, the idea then is to coat all nonreflecting surfaces with optical black, then mask off the reflecting faces and in/out faces and inject yellow foam into the enclosure to permanently immobilise the prisms, then remove the adjusting screws. That should be pretty bullet-proof for impact damage from being dropped.

The external Agus35 version I built around my original prism path will not have to be altered. It is still made from plumbers parts, a bit bulky but light enough, about the weight of a SLR camera.
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Old October 13th, 2004, 09:22 AM   #1175
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Sounds interesting Bob. Do you have any pics? Where did you pick up the prisms?
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Old October 14th, 2004, 09:05 AM   #1176
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James.

As I am in Australia, the source may not be a lot of use for you except they may know who supplies into your neighbourhood.

The supplier was Francis Lord Optics. Their email is sales@flo.com.au. the contact person who arranged my order was John Schmid. The 40mm x 40mm x 56mm x 40mm thickness on all faces was something they had to order in so it may be available readily in the US.

The designs Chris Hurd posted for me at www.dvinfo.net/media/hart were posted as conceptual information only and attempts to directly build to them should not be made. It's been a while since I made this warning and its probably buried a bit deep on this discussion by now.

I have some other committments right now so have not advanced the drawn designs any furthur to the point of reliability.
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Old October 15th, 2004, 11:11 AM   #1177
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Ok this may be dumb but...

Why is it that people use GG adapters instead of an purely glass system?

It wouldn't be that hard to design a relay type lens which would compress the 35mm frame size down to that of a 1/3" CCD.... In fact I have been thinking about designing such an adapter.

My only question though: would this retain the 35mm depth of field? I can see good arguements both for and against the idea...
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Old October 15th, 2004, 11:25 AM   #1178
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It would not retain the DOF.
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Old October 15th, 2004, 01:37 PM   #1179
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Can you explain why that would be?
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Old October 15th, 2004, 11:49 PM   #1180
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Brett Erskine:

I gathered from some posts that you are the resident expert on condensor lenses.

I am trying to narrow down what to purchase from opto sigma, as I don't want to buy 5 or so lenses. What is your advice on focal lengths for pcx condensor lenses, as well as any general advice on condensors.

this is the link i plan to chose from:
http://www.optosigma.com/miva/mercha...herical+Lenses

If anyone else can field this question, have at it. I am starting the arduous process of trying to build an adapter for an xl1s, as it seems that no one but Dino Reyes, who seems to have disappeared, has been at all successful in building an adapter for this camera. Now that the xl2 is out, it seems like this adapter would be in high demand. But alas, the groundbreaking is yet to be done.

If anyone is curious on the progress, or wants to lend their knowledge, I, and everyone else involved would much appreciate it. Both threads:
http://dvinfo.net/conf/showthread.ph...5&pagenumber=1
http://dvinfo.net/conf/showthread.php?s=&threadid=23451
are being posted in.

we have decided to try to build from scratch, using an achromatic doublet as our relay lens (20-25mm), a pcx as condensor, and gg from optosigma (1500 grade).

stephen birdsong
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Old October 16th, 2004, 04:19 AM   #1181
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Stephen.

Awhile back, I did some rough and ready tests with "C mount lenses into a 1/3" Kampro single chip security camera. The results I posted on one of the XL1 discussions.

Do C-mount to Canon XLI/2-mount adaptors exist or is the back of the C-Mount lens too close to the filter face in the XL1/2 optical path? As a macro lens, the C-mount lens I tested with had to be mounted about 3mm furthur away from the camera focal plane.

With a bit of luck, this extra distance forward just might allow enough clearance to fit up to the XL1/2s and not touch the camcorder's internal bits. A small C-Mount lens body may fit back inside the XL1/2 mount if it has to be brought closer to the image plane than a 35mm still-camera lens might be able to be positioned.

The task I guess is to find out from someone who pulls the cams apart for a living :-

If there are any extra internal lenses in the optical between the mount face and the CCDs. I have seen reference to "on-chip" lenses in Sony and JVC 3xCCD products.

What is the flange to focal plane distance? Given that dimension, it should then be possible to test with a single chip security camera to find the right lens focal length.

Don't take too much notice of my comments. I'm full of theory and not much proven fact on this subject.
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Old October 16th, 2004, 08:25 AM   #1182
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Quote:
we have decided to try to build from scratch, using an achromatic doublet as our relay lens (20-25mm), a pcx as condensor, and gg from optosigma (1500 grade)
Let us know how this works -- my bet is that 1500 grade GG will show noticable grain, especially with the higher-res sensors of the XL-1/XL-2.

- jim
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Old October 16th, 2004, 11:47 AM   #1183
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Jim,

If 1500 grade is not fine enough, what alternative to I have?

Bob,
I *think* c mount to xl adapters do exist. The fortunate thing about c-mount lenses (perhaps all lenses), if you increase the flange depth, you decrease your min focal distance. Thats a bit of information I got from a schneider optical engineer. Schnieder makes the lens used in the mini35 xl relay lens.
From what I understand, a c-mount lens would not need to be behind the cameras flange, or in other words, in the recess of the camera body, it would be able to mount similar to the stock lens. I vaguely remember seeing an adapter for c-mount, but it was pretty pricey.

stephen
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Old October 16th, 2004, 09:04 PM   #1184
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Quote:
If 1500 grade is not fine enough, what alternative to I have?
1) Accept the look of the grain.
2) Rotate or move the glass somehow.
3) Perfect a micro-crystalline wax screen.
4) Pioneer a new focal plane material :D

- jim
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Old October 17th, 2004, 04:36 AM   #1185
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Stephen.

1500 seems to be about the practical limit. You can force the grade in the slurry to become a little finer by working the grit to exhaustion but that will require a machine as you will become exhausted before all the particles of the grit do so, ie., there will remain one or two larger particles which will get back into the mix when you get almost to the end if you do it by hand and you will have to start over. (Do the words RSI mean anything.)

I found that forcing the slurry yields a finer groundglass texture but this then results in a partially transparent groundglass. I understand 3 micron does the same thing. The partial transparency improves light transmission and apparent sharpness but causes a sort of halo or ghosting effect when highlights in a softfocussed background are overlit. Normal lighting and compositional practices can resolve this but the image does have a slightly surreal and un-natural look. It would work great with a human face in a dark environment overlit by only a key light as an effect.

I am also using a spinner and cannot vouch for how uniform the texture from a forced slurry will be across the grounglass.
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