Homemade 35mm Adapter

[Richard James]

Thanks Devin, Look foward to seeing your final design and footage:D

[Jim Lafferty]

Daniel,

Are these the clips you speak of at bobflash.com.br:

Clip 1

(bobcam-natalbarrozo-01.wmv -- 4.07mb)

Clip 2

(bobcam-natalbarrozo-02.wmv -- 3.47mb)

?

For future reference -- when posting clips, please include the file name and/or size in your post -- that way we know we're getting the right material.

- jim

[Bob Hart]

If having trouble getting the CD disk to run true, three solutions - (1) Use the whole of the CD spindle system including the pressure plate which clamps from the opposite side. This is supposed to let the CD find its correct position through gyro effect with the inner hub acting more like a clutch and centre rather than an alignment. The motor remains hard mounted. (

2) If this can't be done because of limited space and you have to mount the CD rigidly to the spindle, try making a diaphragm mount for the motor if the motor is of face-mount Mabuchi style construction. Make a little thin disk or square out of something really light and pliable. Shim steel would be best. Ice cream or milk container is okay but it will deform out of position in time. Face-mount the motor to this. You'll need to be able to precisely drill 4 holes through it, one for the motor spindle shaft, three for the screws.

( A quick and dirty cheat for making a template is to place an identical motor face down on the platen of a scanner or photocopier. The spindle shaft will have to have been removed though some photocopiers or scanners will accurately scan an object up to half an inch away from the platen. - So you'll probably have to have a second motor to dismantle for this. Slide-tray CD players often
have similar motors for tray and transport drives so these could be used. Print the scan and check the distance between the holes against the motor. Glue the print to the metal or plastic you want to drill, mark or centrepunch through the paper then drill through it. Printing to a sticky label makes the job even easier.) Mount the plate or glue it to the case. When the CD runs up to speed and straightens out, the motor will be seen to be vibrating slightly.

(3) Make a foam rubber sock out of hotwater pipe
insulation. Fix your spindle motor inside this and mount the foam inside a piece of plastic pipe glued to the case. It may be harder to keep the motor is position though as the material will slump in time.

[Bob Hart]

For Aussie visitors, with Chris kennelmaster's help, there may soon be a .jpg of a partly assembled early prototype of the Agus35 non-inverter rotary groundglass principle, using Australian standard PVC plumbing bits for case and lens tube structure, plus a Decor potplant saucer as a soft motor mount. (Yes the sock will be there).

Once the motor and disk image plane positions have been tied down by testing, the lens tube will be shortened to accept a proper lens mount for the objective lens and some sort of attachment, probably 58mm filter thread for the PD150 at the other.

There will be observed a cut-out in the lens tube insude the enclosure. This provides assembly clearance for the motor and disk mount which clips into place. The enclosure case comprises two riser caps and a short piece of pipe inside one purely as an internal guide sleeve for case assembly.

The disk sits ahead of the orange saucer driven by the motor mounted behind - not fitted in this illustration. The battery holder will fit in the rear enclosure with the motor and the switch will be mounted to the rear cover which will be the removable cover for maintenance.

Fixing of the covers will be by long pillar nuts and screws as used to mount circuit boards.

[Zac Stein]

bob sounds great... looking forward to seeing it.

I have some webspace, just email me zac@mindfreeproductions.com

Zac

[Daniel Moloko]

yeah,

these are the clips

i just told about the clips, xmas ones, 24th ones.

thanks

ciao

[Chris Hurd]

Bob Hart's images now online at www.dvinfo.net/media/hart.

By the way, I've finally edited a boiled-down version of this thread which you can read at http://www.dvinfo.net/conf/showthrea...threadid=18950 -- but continue to post responses to this one, please.

The edited version has been chopped down to about half the size of the original, but if anyone sees more stuff in it that can afford to go away, please let me know. Hope this helps,

[Bob Hart]

In relation to using fibre-optics for image inversion I enquired with Electrophysics Corporation in the US who make the Astroscope line of camcorder image intensifiers and have received advice which indicates fibre-optics would not suit our application.

Their representatvie was most co-operative and gave a prompt response even though I was not in the market for their product.

An extract follows :-

"""
Clearly the prism/mirror approach would be lower cost and better performance. There is no existing production of image twisters having 35mm format. In addition, performance will be degraded in several areas:

1) There will be a significant reduction in effective F-number from the coherent fiber bundle (they usually have about 30% transmission);

2) Resolution (MTF) will be significantly reduced due to the limited size of each fiber;

3) They will be costly.

""""
(End quote).

Therefore, it's back to the lenses, mirrors and prisms. Well it was worth a thought.

[Nicholi Brossia]

Wow, that's really cool that they were so informative.

[Jim Lafferty]

For those of you who are looking to build an Agus35 for your GL1/GL2, I'm in the final stages of mine (read: sanding epoxy down and applying the last coat of black paint).

I had it up and running a moment ago and the image is stunning -- the pre-frosted disc makes all the difference in the world, and using a CD motor makes this quieter than a whisper.

Here are the pics:

http://ideaspora.net/agus35/final/front.jpg

http://ideaspora.net/agus35/final/rear.jpg

http://ideaspora.net/agus35/final/motor.jpg

http://ideaspora.net/agus35/final/disc.jpg

http://ideaspora.net/agus35/final/full1.jpg

http://ideaspora.net/agus35/final/full2.jpg

Footage up later today.

- jim

[Agus Casse]

<<<-- Originally posted by Jim Lafferty : GREAT NEWS!

I've discovered where to get pre-frosted CDR's like Agus uses -- Maxell's 48x/700mb 50 spindle has it!

I found this on sale at Tower Records today ($15.99), and since I just ripped the label in order to open the pack, here's an idea of what it looks like:

http://ideaspora.net/agus35/frosted.jpg

- jim -->>>

Hey there Jim, i bought the same spindle,but the label is green, and unfortunaly it didnt came with the frosted CD inside...

Try up finding the blue label ones instead.

Agus Casse

[Jim Lafferty]

The label on mine was blue with a green tint -- sort of a deep aqua. Dunno why yours didn't have a frosted CD? I'll pick up another spindle next week and let you know.

- jim

[Jim Lafferty]

Well, I thought I'd have footage up tonight, but I've just come home and there's a long render ahead. It's 12am and someone's waiting upstairs for me :)

However, as proof of the improved imagery I've grabbed some full-res stills from the footage I shot around the house today. Be aware that it is not "well lit," and was intentionally so -- I wanted to see what the adapter would produce under "normal" circumstances.

Also, there can be seen some minor vignetting in a shot or two -- this is because my adapter is still without a rail setup and consequently there is noticable movement when the focus ring is adjusted on the 50mm lens -- the adapter will occasionally slip out of alignment, bringing vignetting into view. Hopefully I'll have the rod setup done by week's end.

This room is lit by minor exterior light and two 60 watt bulbs. I shot it at 1/60th, f/2.0 on my GL1, with gain set to 6 (yes, I'm aware of grain produced...)

Here you go:

http://ideaspora.net/agus35/teststills/

- jim

[Agus Casse]

Those looks really nice, dont worry about the grain and lowlight... if you light up more the scene, you will be able to reduce it, same happens with the TRV18, i need to put it like 5-6 steps before the max exposure to get some low grain image.

Also, you can underexposure and then light it up in post.

[David Mesloh]

Hi all, I just started reading this thread so I apologize if this has been brought up already.

There is an optical concept where if you wave a stick up and down very quickly with your hand and wrist (like swatting a fly)you can project an image on the plane that the stick passes through. the image appears to be visible in mid-air. My observation is that if you had 2 or maybe 4 propeller-like white arms at 90 or 180 degrees to each other, and had them spinning fast enough, the image would appear on the plane where the arms were spinning. An easy way to test this yourself is to take a slide projector or LCD projector or film projector and hold a piece of paper about 5 feet in front of the lens and focus the image on it. Then remove the paper and while moving the stick up and down rapidly, you will see the image where the paper used to be. The optical principal is called Persistence of Vision.

I will attach the sicence part of this as JPEG's for chris to post.

David Mesloh
just lurking on this one.

I'll attach