Homemade 35mm Adapter

[Filip Kovcin]

he, he, i already tested it some time ago, and it works.
(shame on me, that i didn't tell you...)

if you are looking for it - just find the cheapest binocular but not with porro prism. the other one - straight one, with that schmidt roof prism. i found one here in poland for 4$ - used one, and bit out of order, but that prism part was not infected, and this works for me. to be honest the picture inside that prism is little bit too small, but it definitelly works. and by conisidence fits perfectly without any glue to rubber eyepiece of my pd100.

filip

[Joe Holt]

Yes! Shame on you for not sharing! ha ha.

I too have ordered the close-out mounted roof prism. I also ordered two other mounted errecting prisms from that site. They should arrive by week's end. I WILL share which of the three work the best.

Is there anyone else holding out on us???? Now's the time to come clean and spill the beans. They say confession is good for the soul. It can't hurt our adapters.

Joe

[Wayne Morellini]

Her is a link to making your own HD camera, it includes a reference to:

Minolta manufacturers some high
tech GG called lentilinear???, or
something that consists of many
micro sized lenses that make the GG
brighter. They may sell us the
material.

In it's homemade idea.

http://www.cinematography.com/forum2004/index.php?showtopic=434

I have to say, that it should be perfectly possible to make a projection plane that takes the projected image, and projects it directly forward like a laser, or on low angle, or even straight towards the image plane (progressively narrowing the angle as it reaches the centre of the image). Result would be near 100% light. If you asked the optical manufacturers some of their staff should know something, if you searched through the US and EU online patent databses you should be able o find references to all the designs under the relavent section. A image plane of the first sort would just consist of a surface array of microscopic condenser lenses.

[Bob Hart]

CD sized optial glass disks have arrived - nearly. They're in customs.

Preliminary methods for mounting these thin disks for hand dressing/polishing are likely to be to use doublesided adhesive tape cut into small 10mm or 3/8"squares to stick glass to a plane metal surface.

Spacing between adhesive squares to be about 1mm or 1/16" to enable entry of solvent to dissolve adhesive. Whole disk to be dipped and left to enable removal from metal surface without mechanically stressing the disk.

The optiCal people I have been observing have not been polishing glass on glass but using a steel surface to polish the glass against, so I shall try doing the same. this may reduce the scratch problem.

[Bob Hart]

Furthur to above, I got the Ohara disks out of customs hock.

They are light enough that the CD motor won't have any trouble spinning them and they are concentrically true.

The downside is that because they are raw cut disks, I now have to polish the front side to clear transparency. the machine at the optical shop takes about an hour to polish a glass lens.

Unfortunately my disks won't fit within the workspace of that wonderful machine

Based on the number of orbits per second I've got four hours of rubbing ahead of me by the armstrong method.

[Bob Hart]

Impatience has prevailed and I have shot some footage through an optical-grade glass Oharadisk which is as yet hastily and incompletely finished.

I have asked Chris to post some images. These are named "agusgla1.jpg" through to "agusgla7.jpg" with number 5 missing. If they are posted they will be found at www.dvinfo.net/media/hart

The disks come in raw unfinished form and are described as cut disks.

The first one spins up on the CD spindle just fine and runs truer than the plastic spacer CD I have been using.

The front surface of the glass disk which should be shiny I have only yet dressed to what might be best described as a satin finish. The rear groundglass face is still the raw form as received.

I was curious to see whether the unfinished front surface, which is a shiny plane surface with pits in it, whilst partially transparent, might also perform much like an anti-reflective coating to reduce flare from internal reflection within the disk.

The results are of course soft and I did not take meticulous care in setting up the backfocus and focus of the lens itself with the tests which were with the camcorder handheld. I wanted to see how it performed for contrast.

The SLR lens was the CIMKO zoom I used on the music video. For comparison through the unfinished glass disk and a finished plastic CD-R disk, the files "mtatk2f1.jpg", "mtatk2f2.jpg" and mtatk2f4.jpg" can serve as references as these were shot through the same lens.

[Bob Hart]

Update on the glass disk.

So far, contrast and colour is good with nice whites. Resolution comes up in moderately dull lighting conditions - just, to the pressed groundglass/backpolished plastic disk but texture or "grain" is more obtrusive.

In bright light or strong highlights, sharpness falls over and the image bright spots bleed more into surrounding image.

So far I have polished the front face clear and the rear face to 300 grade aluminium oxide opacity. I have to try for a finer finish on the groundglass face, or give the boss-screen method a try with two clear disks.

[Alex Raskin]

Anyone knows part number/how to order the Minolta's clear focus screen that supposedly has no grain and no markings?

[Wayne Morellini]

Strange how people don't seem to want to talk about that in this forum, do you have a link? I asked about something like this recently, as well. What ever the case is, the wavelength of light, should enable a screen to be made with a grain far beyond HD.

I have a number of links to technology they use to control and diffuse light in LCD pannels (3M is a good source). They tightly controll light, and it's direction. What ever we get we want the lght rays from the projection to go straight down to CCD size (like a laser, so no 35mm DOF loss), how to do this is another thing, but most attempts so far try to do this. Maybe a projection screen that shoots straight and then a lense to downsize the straight rays, for 3-10% light loose through the projection system. I haven't got time to sort out the refs on this yet, but it is there for anybody to look at. 3M optical products (I think they are the leaders), the Society of Information Displays (SID) has a list of Manufacturers and products, and I have seen about three new style high gain screens (no they don't produce light, they shine it over a more limited angle), one that can be stuck on plain glass, floating around here.

Thanks

Wayne.

[Bob Hart]

Wayne.

I guess in my case it is what I don't know about I haven't talked about. I did enquire about fibre-optics and there are products which can invert and others which can reduce image size in the sense that I understand you suggest. The advice given me was that the resolution would not come up to our requirements.

My modification of a night vision unit to a PD150 would seem to bear this out. There seems to be a 500 TV line limitation though a new product offers sharper resolution which suggests fibre-optics are getting better.

The 3M material seems like it has to have already an existing planar image immediately against it. Of itself it may not be able to behave like a groundglass screen. One would have to have a piece of it to find out.

The material may confer benefits such as less bleeding of highlights into surrounding image which might be aggravated by the relay lens into the camcorder.

For myself, I have too many committments for me to go down another research path at present before I find this one to be a dead-end if it turns out to be.

[Wayne Morellini]

Understood, it is only a suggestion for research, as there is still some optical issues with the present scheems. I too have about 8-10K of printed research pages left around here (most not read), and have spent 100's of hours in relation to some specific display/projection subjects (with an earnest desire not to do so again). While one manufacturer might not have the right product, that doesn't mean that another doesn't have a much better version of it. Maybe if I spent another 100 hours I may well find a extremely good projection material, but maybe this Minolta has something real to offer us (have to look it up).

[Bob Hart]

I think there are some optical effects filter products which perform similarly.

The purpose is apparently to confer a soft image with sharp highlights and microlenses is the way it is achieved.

[Bob Hart]

RE: Prism image erector for Agus35.

I have sent an updated conceptual diagram and support note to Chris Hurd in hope he can post it with the others on

www.dvinfo.net/media/hart

There is much more to be done on it and hopefully, someone with superior electronic drafting skills to my own (nearly none) might be able to translate original 2D plans to 3D model. I have tried and failed. The drawings can be provided in .tcw and .dxf formats

So far it seems the most practicable method will be to make the prism array in craftwood. This material has very small particles and remains reasonably stable if not dampened.

The disk motor drive plate will have to be fastened to it or kept in accurate alignment. The whole assembly will have to be movable for either backfocus and final axial alignment purposes.

This could be achieved by having the motor mount plate adjustable with three spring loaded screws or pillar bolts/nuts which would give two directions of angle and one of adjustment parallel to the lens axes.

Separate fixings would have to be used to provide parallel adjustment across the lens axes.

This might be as simple as three spring loaded set screws tapped into the outer case and oversized holes in the mount plate and oversized washers for the mount plate screws to permit a lateral sliding movement.

Provided the initial build accuracy is accurate, this second adjustment method should not be needed but might be sought by builders concerned with precision.

The precision issue is not with the image from the 35mm camera lens onto the groundglass as the 35mm motion picture frame is smaller that the frame the lens was designed to project.

Critical positioning of the disk outer edge and prism edges will already be fixed in the prism mount/disk motor assembly.

This method however is a very significant departure from the original simplicity of the Agus35.

Desirably, the prism/disk motor assembly would be a separate assembly from the rear camcorder lens mount to reduce noise. The CD-R case would cease to be a structural element and become a simple cover for the groundglass disk.

[Chris Hurd]

They're posted now, Bob -- thanks,

[Bob Hart]

Thanks Chris.

To all.

RE: DRESSING AND GRINDING DISKS.

I have been scheming and planning for means of
cheaply automating the process. The machine is yet to be completed and the following is all unproven theory.

So far it looks like being a gemstone tumbler style thing :-

1 x washing machine AC pump motor.

1 x automotive engine water pump. - or -
1 x automotive power steer pump.

1 x oversize elastic band or flat drive belt.

1 x 50 disk CD-R case outer cover.

1 x 25 disk CD-R case outer cover.

1 x 25 disk CD-R case inner spindle. (Pillar cut off).

Several scrapped CD-R disks for spacers.

One custom brass donut shaped roller, with deep
concentric grooves cut in it about 2mm (1/16") apart.

1 x door hinge.

3 x pieces of chipboard or scrap ply panel.

Assortment of screws gutter bolts etc..

METHOD:

Water pump or power steer pump is mounted by its
bolt-holes to a wooden panel. A clearance hole may
have to be cut out for the impeller.

The 50 disk CD-R outer is mounted to the pulley with bolts or screws. Use sealer or contact adhesive on the heads to lock them.

The washing machine pump motor is mounted to drive
the water pump or power steer pump with a flat belt straight off the motor shaft like a flat belt turntable. (The plastic pump housing, seal and impeller will have to be removed. The plastic seal retainer may be an integral part of the motor and have to be retained for mounting purposes.)

The timber panel is mounted to a base plate with the door hinge. The third piece of timber is a prop. Another door hinge could be used and nails or screws used to make a ledge for the edge of this to hold the main panel at the correct angle.

The whole thing will look like a small cement mixer.

The CD-R 25 disk outer case will slip inside the 50 disk outer case. They are handily tapered. It needs to be removable as it will wear out. The spindle with its pillar cut off is now a lid.

The spacer disks may have to have the centres cut out and stacked until the centre hub of the CD-R case no longer touches an entire disk and the disk will sit flat and steady. These might best be glued in place. The glass disk sits on top of them.

The brass donut rolls along the face of the glass disk in a polish slurry. The tilt angle has to be adjustable for best pressure versus the disk continuing to roll smoothly. The tilt must also be there to keep the slurry pool inside not on the floor.

My version uses a Ford 6 cylinder automotive water
pump. This yields about 70 rpm with an AC 50hz electric washing machine pump motor driving off a 4mm approx shaft. For 60 Hz motors, the larger power steer pump pulley may be needed to keep the drum speed down. Buick V6 water pumps have a larger pulley but may be more awkward to mount.

All the automotive water pumps are doing is providing a bearing, a pulley and something with bolt holes in it to mount it with.

For the Aldu disks, a much smaller drum, maybe a small plastic food jar with a pressed lid and a smaller donut would be needed. For contact pressure the donut might have to be thicker for weight. In both examples the donut should not cover more than about 5/8th of the disk diameter otherwise the rolling action will become erratic.

The motor and pumps should be found in waste bins at repair shops. Whilst components essential to their function as pumps may have become completely ruined, often the bearings and the electric motor in the case of the washing machine pump remains serviceable. Do not wire the motor up yourself but have a qualified electrician do it for you.

No warranty of satifactory performance is made either express or implied.