DIY spinning 35mm adapter discussion

[Bob Hart]

Roll up some cardboard cut into strips with straight edges and exact width edge-to-edge tightly around a broomstick. Pull it off and let it spring out inside the Pringles tube. Unravel the coil so that it becomes tight in the inner diameter of the can and you now have a fairly accurate shoulder to locate your achromat against.

You might have to join a few strips end-to-end with stickytape to get a long enough length to make a thick coil. Do the same to make up the space around the rim of your achromat. Use PVA wood glue, the white stuff. Shove pins though the tube to hold the shoulders in place until the glue sets.

To hold the Nikon lens in place when I did my initial set up, I rolled the lens up in a footless sock and shoved that in the tube from the front.

[Terry Lee]

I shall try the cardboard technique soon! Thanks!

About the extension tube, I would construct the tube for the achromat that has a male end toward the camera, and a female toward the front. There I will be able to screw on the extension tube which will make up the remaining length TO the box or THROUGH the box where I will be able to directly attach the lens mount?

Bob, thanks alot for the help. This is very much a joint effort. Couldn't have built this thing with out your help!

Terry.

[Terry Lee]

given up on me? :(

I found this lens mount on ebay... would this work?

lens adapter flange 4 Nikon F AI AIS convert to 55mm 55 - eBay (item 360167019961 end time Aug-31-09 04:59:25 PDT)

[Bob Hart]

From about 5000 miles away it looks okay to me but I am a bit nearsighted so don't sue me if it goes pearshaped. There appears to be a conventional spring behind it and a latch pin. The thread is said to be 55mm. You may be able to screw extention tubes on behind.

The latch pin release on this style of mount tends to bind after a while. Even the P+S Technik one did. Drop a bit of machine oil in under the sliding button every now and then and wipe off the excess. After a while, the light fractions come off the oil, the residue seems to endure and problem solved.

If you experience a jam, don't get the red mist and armstrong it. Gently manipulate the lens back and forth against the pin as you apply light rearwards pressure to the release button, maybe touch a drop of machine oil under the release button.

If you can pull the release button outwards in its clearance which is about a paper thickness above the surface, slide a bit of paper under the rear edge of the button and try again - usually works - by reducing sideload and friction on the pin itself

Don't blame the designer-manufacturers. There is pretty much no other way to do it due to the confined space available.

[Terry Lee]

Alright thanks Bob!

If I stick an extension tube behind it, would that tube extend all the way from the lens mount, through the box and screw onto the achromat? I would then have to cut a clearance in the extension tube for the GG to slide up in the view of the lens correct?


Terry

[Chris Barcellos]

The photos below are of a simple design I had going before I found and fell in love with the Canon 5D.

I used the Redrock spinning disk that they were selling for about $45 at the time. I was in process of firming up the motor mount to make it adjustable so I could get the spinning glass exactly set properly both distance wise and on right plane.

Used extension tube on lens end, and a tube with 58mm thread on other to make things easily adaptable. I had some good first tests, though the shaft on the CD motor I had was a bit noise and drifted some. Focal plane would shift a bit on pointing camera down.

The two tubes aligned because they were mounted on a piece of channel aluminum.

Cover on both ends of the sewer pipe were from nut cans.

[Terry Lee]

Pretty cool Chris, thanks for posting.

I understand from what Bob has told me that the most important thing is getting everything optically aligned so I am trying to pay as much attention to that as possible. So what I am trying to figure out is if I can use an extension tube straight through from the achromat to the lens mount. It makes sense to make it a single straight tube as a guide from front to back. I am just worried about giving the GG enough clearance. I don't know how extension tubes are constructed and if I can cut a clearance slot in where the GG will intercept the view of the lens.

[Bob Hart]

Terry.


Chances are, you may make an error with the first cut for the disk clearance so my preference would be to mock up a tube with cardboard or pvc pipe and experiment first.

A rough method of marking out cuts which are square-on to the centre axis is to get a strip cut from a piece of paper with a known straight edge. Wrap this around the cylinder or whatever it is you want to cut. Slip and adjust the wrap until it becomes straight around the known straight edge, then mark to the edge.

You of course don't need to go to this torment if you have a square front edge to measure back from.

You likely will have to make a second cut to clear the electric motor as well. So your cut may look something like a letter "T" with a very thick shank where the motor goes.

When you cut your tube with a hacksaw, do not try to cut through with the blade of the saw steep-to the job once you have made the first initial penetration. Instead, lead the sawcut around the tube.

It is a bitch job because the saw jumps out and scratches up the surface finish and takes a bit of practice. I start a reference cut and lead it around the tube by using my thick thumbnail as a cut-against guide. Your thumbnail should last about two or three inches before it starts to get a bit thin.

Once this cut has been made in the tube, the tube itself will become weakened. The size and tidyness of the clearance holes you cut in the case will be critical for strengthening the tube.

This weakness is not necessarily a bad thing as it establishes a soft failure point in the event of the combination being dropped, hopefully protecting the camera a little.

I relied on adhesives fixing the tube to the front cover and a very tight tidy clearance in the rear cover for support. For me this was easy as I was using pipe plastic. Metal is a different story.

However this may permit the tube to warp off-axis.

My personal preference would be to add a spacer or rib from front-to-back between the intact upper side of the tube and use three small through-bolts to fix the tube to the upper surface of the case through the rib or spacer. This will ensure the tube remains straight and the optical axes remain co-incident. You will see from Chris's photo, how this spacer rib works except that my suggestion places it inside the case not outside as is Chris's arrangement.

If you can cut a circular contour along the spacer or rib to act as a chair for the round tube, this would be a bonus, albeit probably un-necessary extra work.

If you are at the stage of mounting your motor to the case, examine the adding of an adjustment system. It really enables you to finesse the alignments if you are able to adjust whilst viewing the image rather than having to view image, shut down, add shims then switch on again.

I used a simple flat plastic panel to support the disk motor. I found that the CD disk spindle motor is best supported from the front of its case where there are usually two small threaded screwholes. In most CD players, these holes are redundent as the motors are characteristically supported from a circuit board by the solder tags on the back. You will have to rat a whole lot of electronic appliances from the annual roadside collections, just to find these screws.

Why not support the motor from the solder tags on the original PCB. No reason why not I guess except that a glass disk is heavier and if it runs out will vibrate the motor, maybe fracture the tags over time and the image may jitter as any runout has mechanical advantage over a rear mount arrangement.

You will have to drill a clearance in the plastic for the shaft to pass through. A soft plastic like polyethylene is better, sometimes sold in white sheets of 3/16" approx thickness for whiteboards.

It is a little flexible but over the spans you will work with this will not matter. What does matter is that it is quieter than hard plastic or metal.

Take care when selecting the screws, that they are not too long otherwise they will enter the motor case too deeply and impact the spinning motor armature or lock it up altogether.

End float of the motor armature. In the CD player, this is controlled by a floating nylon fixed pin or ball-end inside of the springloaded or magnetic dummy hub which clamps the CD disk onto the motor hub. It will be iimpractical for you to attempt to install this to your adaptor as it is a mongrel to centre and cannot be made adjustable except if it is supported by a completely separate case structure within the case you are making.

Spacer washers between the spindle hub and the front motor bearing are about the only thing you can do. These are difficult to make and tend to baulk the motor if you happen to pick up the case instead of the front face of the oilite bearing bush inside the case. You will find that the magnetic fields of the motor will centre the disk in operation. This is okay for level operation but when the camera is tilted, there may be a focal shift or jitter.

I used 3 fixed threaded pillars to support the panel. There was a sturdy coil spring between panel and case, a washer between spring and panel, a washer between panel and a nut and this nut to pull the panel against the spring to achieve adjustment.

Use the tail of a vernier from lens mount flange to front of disk to find an initial adjustment. 45.5mm is a safe start. Fit a normal 50mm or longer Nikon lens, then sight it on an infinity target with the lens focus set to the infnity mark.

Pick a significant distant spot like a radio tower. Test the sharpness of this object at all points in the image frame. You will experience a lot of frustration as all screw adjustments interact a little.

Three screws arranged on 120degree centres around the disk ( Mercedes Benz star shape )will all act additively upon each other's adjustment.

However if you follow my arrangement of two screws on 180centres and a third screw on a 90degree centre on the bottom ( Letter "T" shape), then the two screws on 180degrees act additively on all other screws but the screw at the 90 degree centre acts subtractively, with an increased effect towards the outer (upper) edge of the disk.

There endeth the lesson for today.


Chris.

That appliance of yours looks even more sinister and lethal than mine.

[Terry Lee]

Hey bob, Thanks for explaining all that to me. Sorry I don't always reply quickly. I normally read your post when you post it and go try to apply what you said to what i'm working on.

I bought another cheap achromat off ebay for like $20 that is 72mm. The one Wayne sent me is actually a 58mm.

Good call on the pringles can. The 72mm fits perfect.

[Bob Hart]

Wayne's 58mm should be fine. I have been using Century 58mm in 58mm to 72mm threaded rings and even a 58mm to 77mm on an EX1. There was however corner softness which is a unique trait with the EX1 lens system.

The 72mm will give you a little more wriggle room in finding a best position as in distance from front of camcorder lens. There may be a little interactivity between zoom position, camcorder lens forcus and the position or distance of the achromat from front of camera.

There may be positions which introduce a barrel distortion = ((--)) or pincushion distortion = ))--((. The trick will be to find the best compromise.

Take care not to bark at shadows - the camcorder itself may have distortions in the image so check all zoom and focus positions in the range you intend to use against rectangular targets with straight lines drawn across in a grid pattern.

You will likely also discover that not all camcorders were born perfect and free of blemish. Many will have a point in the zoom range, usually at the long end, where there will be an observable brightness falloff in the corners if you point the lens at a uiniformly lit plain surface, another shadow you will bark at. Unfortunately, this artifact is additive to the inherent nature of groundglass devices to darken the corners when wide stills lenses are used.

If there is a camcorder image deficit, it is best to know about it from the start rather than be chasing an impossible dream and find out way later down the track.

Enjoy. - Take care not to drill through anything into punching holes in the furniture or kitchen counter bench.

[Sean Vincent]

I built my own spinning disc adapter earlier this year. It took me a day and cost me £30.

It's pretty much the same design as the others you see on the net... i ripped apart an old CD walkman and fitted the motor to a switch and battery and mounted it all inside a plastic box from Maplins. I got very lucky with the measurements for the distance to put the disc in relation to holes i cut for the lens mount and the macro lens. I made the disc from a clear CDR that comes on the top of the bulk packs and hand sanded it...i have one which is less sanded which gives a different look.

I bought the macro lens off ebay for about £10 and used a back-end lens cap with a hole cut in it for the lens mount. It was all fixed together with a hot glue gun.

Now i wasn't expecting much...but when i mounted it on my DVX100 and then fitted an old chinon 50mm lens to it i was very surprised. It took a minute to get the zoom and focus on the DVX to sit just right on the spinning disc...but i got there.

The images looks great. Ok, a bit murky round the edges but very usable for some arty kinda shots. I even used some of the shots i got with it in a feature.

I always planned to by the Letus... but having seen the Lumix GH1 and Canon 5Dmk2 in the last few months i think i'll go down the DSLR route. 35mm adapters have their place...but i think their market is shrinking by the hour at the moment.

Would defo recommend building an adapter though..pretty easy and will let you decide how much you might actually use one. The upside down image will drive you nuts...so much better to use a cam with a flip function on the LCD.

S