Homemade 35mm Adapter

[Alex Chong]

Hi All,

Alex here. I have been going tru this site for the past couple of months and with all the info i learnt alot and got down to buidling my very own Agus mini35. I finally sorted out the image inverting problem. I am using the pentaprism from an SLR camera and its 45 degree reflecting mirror. The whole set up is installed close to the ground CD and I just zoom in on the image reflected tru the pentaprism using my MX500 (PV953) DV camera. it worked well when i just place the individual items together by hand. So I have no doubt it works when I fit them all together. Its down to getting the alignment right for the whole set up. Will definitely show you guys the pictures of the set up.

I am actually using 2 nos. of 4 inch white UPVC end caps, four 25mm/6mm dia. nuts and bolt (Stainless Steel preferred), 3mm thick perspex glass cut to shape to hold a small size motor and a 90mm dia. cut CD grounded with a 1000 carbon carbide paper. I am using a 50mm f1.8 lens (Very fast) and a 80-210 f3.8 zoom lens for the canon FD mount. great stuff. everything fitfed properly.

I am having problem with the placement of the pentaprism as its offset alot from my agus 35 setup and it kinda look funny sticking out higher than the agus 35. (I know its hard to understand with words but once I send the pics, you will know what I mean) I am trying to send an autocad file or a jpeg file into this forum. How do I do that?

Anyway, thats all for now. will email some more once I got my pictures safed into the computer. I lost my digital camera cable. So can't download any pic.

[Brett Erskine]

Sounds great. Look forward to seeing it. Sounds like you have one of the few compact video cameras that has a lens that can focus and zoom in close enough to see thru the opening of a 35mm pentaprism. Unfortunately this area is too small for most pro-sumer/pro cameras. You lucky bastard ;-) Alright we'll send off thoughs drawings. If you cant seem to be able to post them email them to me at BErskine@mail.com

Good luck with the rest of your design
-Brett

[Alex Chong]

Hi Brett,

Actually, the pentaprism and reflector mirror create a distance between the camera lens and the image on the ground cd. I think the distance is equivalent to roughly 50 to 60mm. I have to infact zoom in 5-6X in order to get a good view. That roughly means placing my camera lens 50-60mm in front of the image. I hope that makes sense. Of course I am not entirely sure but i guess most cameras can focus on something at that distance, if not 2mm distance.

Sure, I am about to finish off the drawing on the proposal and I can send to you.

Alex

[Christian Loennechen]

Hello!

I just read through the entire thread and is feeling a bit dizzy. Ah well, time to start on the Aldu35 thread then.

But! Why is my first post ever in this thread?
Well, I e-mailed the MOVIEtube people, asking for an approximate price.

Here is the answer:

Hi Christian Loennechen,

the MOVIEtube Pro will cost 14.500 Euros. The estimate price for the MOVIEtube Light is 6.500 Euro.
Thanks for your interest in our product MOVIEtube.

JK-Marketing and Sales-

That is about 18,000$ for a Movietube, and 8,000$ for a Movietube Lite.
Wow! That's a lot of money! Especially if you check out the lite version on their page, it seems pretty simple...

I guess that won't be an alternative. Back to the old plans of making and Agus or Aldu then.

[Alex Chong]

Hi guys,

Finally completed my mini35 adaptor with inverted image. The setup is good but the lighting sucks. Mostly because my MX500 (PV-DV953) sucks in low light. But very good in daylight. Anyway, I can send the images for everyone to see but can someone tell me how to post the image on line. I made the Agus35 version as well. But I am using a small monitor turned upside down to view the inverted video. This version is much better as it allows more light in.

Hi Brett, I can send it to you. I will do that tomorrow as I still have the images in my camera.

By the way, this web page is interesting as it describe how to install and use of the P+S Pro35 adaptor. It even has close up photos of the parts. http://www.dvxuser.com/articles/mini35/

Alex

[Bob Hart]

An update on the raw Oharadisks and the tumbler method of finishing them and dressing out the scratches from failed attempts at a groundglass finish.

The disks are supplied in raw cut form and have to be dressed and polished before a groundglass surface can be created on one face.

So far, the tumbler method seems to work but the conundrum is finding out the right diameter for the polishing disk (donut, roller or whatever it should be called,) It also needs to be much, much heavier than the one I used to polish the glass by hand.

When using the initial coarse grit for dressing out the cutting marks in the glass, the tendency is for the disk to have concentric circles of varying abrasion. Because the donut rolls across the face of the disk as itself is rolling in the tumbler, there are infinitely varying surface speeds between the two faces across the radius of the disk. I would have thought that as high spots occurred, localised pressures would remove the high spots but such is not the case. It may be that the initial coarse cut and intermediate grades of abrasive will have to be done by hand.

As for polishing, a ten minute run with polish shows immediate beginnings of a polished finish, so restoration of disks which have been damaged looks to be an option.

As I mentioned previously, I intend to try dressing the intended groundglass face of the polished disk with 3 or 5 micron AO abrasive by rolling small loose bicycle ball bearings over dry grit on the glass in the tumbler. By this method I hope to create pits, not scratches. I hope it will be also easier to control the amount of frosting effect so that the surface is not too opaque.

The 70 rpm drum speed seems to be okay.

[Agus Casse]

Wow,

I am sorry that i couldnt made a new version of the adapter, the work is killing me. But i really have some good ideas to start making a new version of it. This time i want to really beat the mini35, i think the first shoot was a good start, and seeing how many people got interested got me thinking that i should use again my imagination to come back to this project and make a new and improved version.

So, i will start posting back soon... with a new design of the Agus35 ...

:)

Greetings, and keep the project alive.

Agus Casse

[Alex Chong]

Hi all,

My inverted mini35 was ok but not satisfactory. I have seen better results with static version. The image coming out was abit washed out and I attribute it to the ground CD. It is so difficult to get a properly ground CD. So I scrap the Idea completely and now working on something new.

I got this solution which i think its really good. I was using the focusing screen from my minolta camera (faulty ones) and found that the light dispersion and image formed on the screen is really good. Even my PV-DV953 (which is bad in low light) performed well with it. Then I thought, why not vibrate this screen in a vertical axis using the cam shaft mechanism similar to the car engine. I did a prototype and it worked very well. Except for the vibrations and sound. Its just too much. I am just wondering how the P+S manage to vibrate their GG without creating noise and vibration. I know this method works and the focusing screen really give a good image when put to the tests.

Is there any mechanism out there for models that has this sort of oscillating motion? The distance travelled by the up and down motion need only be 5mm or so to create the effect of a rotated ground CD. And because the Focusing screen is finely made (i.e. no scratches) its perfect. You can use the all matte Type D Nikon screen or the Canon PH screen. (p.s. got the idea from the guys who did the marla video. Thanks)

Agus,

Any idea how to vibrate the screen without so much noise and vibration from the motor. Can you pass me your email. I can send you a schematic of the design so we can all think about how to make it. If this work and I know it will with the proper parts, you can get really close to the P+S equipment at the fraction of the cost.

Alex

[Bob Hart]

UPDATE ON THE ROLLING DONUT IN TUMBLER :-

There needs to be a machined baseplate in the bottom of the CD-R case. Two or three stacked CD-R disks are still too flexible, the glass disk bends and then the donut wears concentric grooves in it.

The donut also has a tendency to hook up then drop across the glass which causes a ripple effect. The face of the donut should have concentric grooves in it at about 2mm spacing. There also needs to be at least eight radial grooves in the donut wearing face and also the baseplate otherwise it is too hard to get the disk off. Even then, the donut has to be carefully slid sideways off the glass disk, then the glass disk off the CD-R or the baseplate whichever releases first.

The outer rim of the donut also needs to be tapered so that the rim closest to the wearing face is the widest part. A tyre (rolling contact) area of about 2mm or 1/10" seems to work okay. This makes the wear pressure adjustable across the glass. More tilt of the drum increases pressure to the centre of the disk, less tilt brings pressure to the outer edge of the disk.

Due to the hollow centre of the donut, a hub builds up in the centre of the glass disk. This is a good indicator of how much wear has occurred. It may not hurt to have the thicker centre. It is not in the projected image area. But it may cause other difficulties in the polishing.

Times for the grits appear to be :-

600 silicone carbide or emery. - 1 hr per face.

300 aluminium oxide. - 1/2 hr per face or until larger pits can no longer be seen.

Polish powder. - unpredictable.

Polish seems to occur within 1/2hr to 3 hrs.

Another stage of 5 micron or even another of 3 micron before polish could be desirable.

Once two faces are polished, the chosen face for the groundglass can be roughened. The best method is yet to be discovered.

[Valeriu Campan]

<<<-- Originally posted by Alex Chong : Any idea how to vibrate the screen without so much noise and vibration from the motor. Can you pass me your email. I can send you a schematic of the design so we can all think about how to make it. If this work and I know it will with the proper parts, you can get really close to the P+S equipment at the fraction of the cost.

Alex -->>>

There is a suggestion of using piezo vibrators. See this post:
http://www.dvinfo.net/conf/showthrea...threadid=27509
I have a GG from a Canon F1 cameras. It has a convex shape top (almost like a fresnel lens). I don't know what will happen with a vibrating optical axis.

[Mike Metken]

Valeriu, nothing will happen to the axis. Mike

[Bob Hart]

FURTHUR INFO ON THE ROLLING DONUT/TUMBLER FOR DRESSING AND POLISHING GLASS DISKS.

I managed to get hold of a piece of soft grey cast iron and turned a metal donut up from that. I did not put the hole in as the bronze version with the hole had caused a hub to build up in the centre of the glass disk. This did cause some problems with the polishing as I suspected might occur.

Otherwise, the iron version is identical to the bronze one with concentric grooves at 2mm spacing and eight radial grooves. The iron roller is not quite as heavy as the bronze. Early indications are it polishes okay but I have not yet gone to clear finish with it.

The hole will remain in the small bronze version for the hand polishing as this did immediately release the disk from sticking and binding.

[Alex Chong]

Hi Valeriu,

Thanks for the link. Unfortunately its difficult for me to get somehthing like this where I live. Is this what P+S are using to vibrate their GG. It will be interesting to know. I am getting alot of vibration from my vibrating GG setup (although the setup is crude) I hope a finer setup will create less vibration. Will still work on it.

Alex

[Brett Erskine]

Vibration can be elimated if you design it to be counter balanced. This will be the big issue for most people if they are designing one from scratch. If its counter balanced right the only purpose for having rubber bushings is to reduce noise. You should also keep in mind that you'll want to make a noise proof housing. Save yourself alot of headaches and keep your eyes open for something ready made that can be adapter for this purpose. Much better than making from scratch.

-Brett Erskine
www.CinematographerReels.com

[Bob Hart]

FURTHUR INFO ON THE ROLLING DONUT/TUMBLER FOR DRESSING AND POLISHING GLASS DISKS.

The hole in the centre of the bronze polishing roller (20mm) turns out not to be the cause of the raised hub area on the glass disk so much as a construction error when machining the grooves. I had in effect skimmed a wider centre hole only .5mm deep of 55mm diameter which was not apparent to me at the time. (More haste = less speed).

The circular grooves probably need to be off-centred relative to each other in pairs as concentric grooves seem to reproduce themselves in negative on the glass disk during the initial surfacing of the disk, how?? I do not know as the centre of the disk is in no way related to the centre of the roller which is smaller. Having fewer, more widely spaced, off-centred circular grooves and more radial grooves in the metal polishing disk may be the answer.