Homemade 35mm Adapter

[Tom Christensen]

I had the macro on for the first portion. I the zoom was in and I hadn't aligned the gg and lens yet.

Macro is similar to what is on this:

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=2977800904&category=29964

I just unscrewed the macro from the w/a. Mine is a little different .45x but same Japan co. It doesn't state the x on the macro.

Tom

[Tom Christensen]

Also

Back image is at

http://www.arcsand.com/back.jpg

my bad.

Tom

[Filip Kovcin]

<<<-- Originally posted by Louis Feng : I have been wondering what stops the camcorder makers to make their lens work the same way as film lens?

If I'm not mistaken a digital camera has the same DOF as film cameras. Can't Sony just use their digital camera parts on the video camcorder? -->>>

the problem is in CCD size. since film frame is aprox. 2,5x bigger than electronic 2/3" professional CCD. so, the DOF is different when the size of CCD is different. all broadcast optics is constructed and work usualy for 2/3" lenses - (read: lenses with mount prepared for 2/3" CCD).

WHEN they construct CCD for whole cameras as big as film frame - the problem will dissapear. of course, none of video equipment producers will just throw their development and research dep. just because we need DOF same as in film. the problem is of course also with the lenses. whey you change your CCD size, you must change the construction of your lenses, so at least 3 major companies will sell then their lenses VERY cheap :)

BUT i.e. arriflex - the maker of most popular 35mm film cameras is working on it. the camera (prototype) is working on proper CCD size - similar to film frame size (bit bigger). and they WILL achieve the same DOF as in film. the arriflex is using normal film lenses.

just a small addition from me.

filip

[Bob Hart]

For Australian visitors to this site here follows a list of some Iplex parts which are worth a look in the event of a 3.5” (95mm) glass disk becoming available for groundglassing. It might be feasable in any event to mount a CD disk on a mandrel and part it down to 95mm OD in a lathe.

Two compact versions of the non-inverting Agus35 could be made. This would include abandoning the
lens tube aligner and returning to the original and simpler method of face-mounting the 35mm lens to the front of the case.

For 7x macro stack or possibly 10x macro if and when it can be sourced :-

Iplex UPVC DWV, DO7210065, 123.100.65, 100X65mm Offset Reducer. for maincase and PD150 mount.

Any plastic pipe that fits the 65mm end of reducer.

Iplex UPVC 65mm DWV, D105.65, 65mm pipe cap. With careful holesawing and filing and face thicknessing, this could be made into a bayonet style mount straight to the PD150. A support stay or rods would need to be added. The lens set
mounts to the 58mm filter thread and clears the inside of the 65mm pipe and cap.

For modified telescope eyepiece lens set adaptor:-

Iplex UPVC DWV, DO7210050, 123.100.50 100X50mm Offset Reducer. for maincase and adaptor which is
to be machined for a snug fit into reducer. Adaptor which carries the lens set, itself screws into 58mm filter thread of PD150.

For both:-

Iplex DIO5100 DWY, 137.100, 100mm UPVC Cap. for front cover, motor mount attachments, lens face mount which can be made integral with the cap with careful holesawing, filing and face thicknessing for Nikon style lenses. For heavy telephotos, a metal mount would be needed. Although the caps are quite thick and firm, possibly a full span metal re-inforcement to prevent downwards sagging would be needed.

Depending upon the type of motor available, a clearance hole might need to be holesawn into the 100mm cap and a smaller cap glued in place over it. The motor and disk in these versions face towards the PD150.

Two 1.5v pen-cell batteries will just fit separately either side of the motor at an angle from the bottom.

Depending upon whether the 3.5” 95mm disks can be had with a smaller centre hole or not, the disk
centre may have to be offset downwards for the hub to clear the image frame.

None of these versions will be ideal for the standard 35mm still camera gate, only the motion picture 35mm widescreen gate, as the smaller disk outer diameter and wider outer edge of the centre hub will confine the image.

I have enquiries pending with Ohara in Japan and Showadenko in Singapore for clear glass substrate
disks.

Ohara cannot supply CD size glass disks in 1mm glass from existing stock. They may be able to supply 3.5” disks with smaller than standard centres.

Why am I chasing glass versus CD disks? My tests so far hint at a superior image with glass. Some
dense bright colours in strong light seemed to bleed together when the spinning CD disk was used. The fixed glass seemed to reproduce the colours a little better. It also may be possible to coat the clear side of the groundglass to reduce internal reflection and scatter from strong pinpoints on the groundglass image.

[Jim Lafferty]

Wow. Thanks for all your footwork, Bob.

I'm about 1/2 done my latest (third) Agus35 design for my GL1, and by now I'm becoming very exacting with how I dismember and slice CD spindles :) Also, I think I could swim for a good bit in the sea of CDR's I've got here...

You can be sure that when I have it done I will be posting comprehensive pics and a little commentary on a website set up for these endeavors. I have plenty of server space and bandwidth for such a project.

...

Someone recently hit on an idea that I discovered myself -- getting proper flange focal length (the distance from the rear of your film lens and the spinning CD) is very difficult to get, more difficult still to maintain with both surfaces parallel to eachother.

The suggestion that you can keep either the GG or the lens moving is a good idea, and I'm currently working on perfecting the latter...I've purchased a 2" molded aluminum hub from Home Depot that my lens will be affixed to, and with a system of 1/4" screws, metal plates and wingnuts, I plan on rigging it to be adjustable.

However, for those of you trying to put together one of these adapters, what has been your experience? Thinking it over now, I suspect it might be easiest to place the CD motor on some sort of telescoping platform...

- jim

[Tom Christensen]

Jim,

I had the same thought. I started looked at breaking apart some Home Depot door hinges and using those to construct a sliding platform along two metal rods extending from the base. If I get lucky, a common rod will be the same size as the hinge post.

Tom

[Bob Hart]

My inclination would to mount the spindle motor on a piece of lexan or any thin stiff stuff, drilled with three holes 120 degree spacing. If making a noise reduction or balance mount, a large holesaw hole through the lexan would suffice to provide the clearance.

Where baseplate to case screws go through, place them as far out from centre as you can go. This will facilitate less tricky adjustment.

Put small compression springs between the lexan and case and use these screws in combination to adjust for objective (SLR Lens) to groundglass back focus and parallelism. Instead of springs you might get away with rubber electrical grommets though these will slump with time. You could also use a huge diameter thin wire spring in the centre around the motor but this would tend to dish the case outwards and the lexan inwards, not good if your nicely black-finished plastic Agus35 is out in the heat.

Hex head (Allen) screws would look cool. When the adjustments are done, lock the screws off with some sealastic.

[Bob Hart]

Tom. It might be my imagination or misinterpretation of your image at http://www.arcsand.com/back.jpg

Are you focussing your camcorder through the centre hole in your CD into the 35mm SLR lens?

For correct relationship between 35mm SLR lens and CD disk see Agus1.jpg on www.dvinfo.net/media/hart

The image can fall anywhere around the CD groundglass zone you want it to as long as it is being projected by the 35mm SLR lens onto it. Your camcorder then aquires this projected image.

If I am getting it wrong please accept my apology and ignore my coments at will.

[Tom Christensen]

No. I am projecting onto the cd as described in the discussion. I used the vise-grip platform to extend the motor up and out and the image is projected on the middle to bottom right of the cd.

Must be a weird angle from my still cam. Look at the image from the front. The motor spindle occupies the hole in the cd.

Tom

[Ryan Henry]

For those who have lots of CDs now...

I discovered that the fake CDs I had were very poorly made compared to the real CDs (out of balance, wobbly, etc) and decided to try a real cd. I just sanded the label side and it works great and is nearly perfect!

[J. Clayton Stansberry]

Ryan,

So, you just took a normal CD-R and sanded that? I haven't heard that yet and am still looking for the fake frosted CDs. Several have posted about the Maxwell's and I plan on searching those out as my first attempts at sanding the clear fake CDs were a bit of a disappointment. Please let us know...thanks in advance...

[Robert Knecht Schmidt]

"Normal CDs" are just thin clear plastic discs with a thin filmy layer adhesed to the top.

[Bob Hart]

I have thought about sanding the real CD-Rs because I have enough dud disks laying around.

Some Sony CD-R "Supremas" 25-packs have clear CDs which are the real thing without the metal and top layers but it is a bit of a gamble because others have the molded ones. You can see the guide tracks on the real ones only if you can look inside the pack - not recommended as the retailer will get upset with you.

If you find one, you have to make sure it is the guide track side you use for the groundglass surface. Lightly scratch the surface near to the centre where you won't be looking through with the back of a fingernail. If it is the guide track side, you will see the guide track partially erased or scratched through.

These disks are optically true, spin true and relay a better image than the clear molded ones. You als sometimes get a bit of rainbow flicker with the molded ones across strong contrast boundaries in your image.

So the real ones sanded back from the metal side should also work.

[Bob Hart]

Quick note for Australian builders. If you are using plumbers parts for a large version, the Iplex 65mm caps for quick bayonet lens mounts, machine in a small lathe just fine if the speed is kept low the cutter is sharp and you don't try to take too much at once.

When "holesawing" using the lathe and toolpost, take care to stop the machine as soon as the disk cuts through otherwise it may turn side-on and wedge the cap off-centre.

Easiest method to mount is to expand the chuck jaws from inside against the inner circumference of the cap. Make sure it runs as true as you can get it so that the mount face you machine is 90 degrees to the centreline of the cap so the lens fits squarely with the lens tube and is square to the groundglass.

After its all done and fitted, back focus is set by how far you slide the cap onto the lens tube. By this method you can have several adaptors for different lens mounts.

[Taylor Moore]

When a 35mm lens with a 50mm focal length is put on to the camera, what does the DV recorded focal length work out to?

Does a 50mm=5omm or a 24mm=24mm.

Or is it dependent on the DV camera lens?

Make sense?