Homemade 35mm Adapter

Bob Hart · February 19th, 2004, 05:41 AM

Matthew

It's best you don't go near your CD with sandpaper or any other paper for that matter if you are going to rub it across your disk. Okay you will get an opaque surface on one face of the disk but the performance will be less than it need be for the same amount of resources and sweat.

You need pits, not scratches on your disk.

The best result will be with a fine aluminium oxide powder of 300 grade, mixed with water and rubbing your disk in very very small circles (quarter inch or less if you can do it) on a very clean glass sheet. This is done without pressing on the disk but allowing the powder to do its work by rolling along under the disk and stamping pits in it, not fixing to a lower surface and then drawing long scratches across the disk. It takes a long time as high edges on the disk rim and centre have to be worn down first. The fine powder may not be readily available to you.

If you use paper, then anything courser than 600 grade will be a waste of time. Preferably you should place your disk facedown on a clean surface, on a clean piece of thin soft cloth.

Place your 600 grade paper face down on your disk. Wet and dry silicon carbide paper is best as pieces are less likely to come off and get on the clear side of your disk and scratch it whilst you work.

Hold the paper from moving across the disk and use a hard round ended object about the size of a pen or pencil and scrub this firmly back and forth across the paper to make the grit press pits into the disk surface. You can automate this process a little by finding an old ball bearing race at your local auto shop or wrecker, holding the centre and using the outer race as a roller. Doing it this way will also save premature wear on the back of the wet and dry paper. You'll need to tilt your wheel slightly so high local pressures occur on the paper. Lift your paper off often, move it slghtly and put it on the disk again. Don't allow it to rub. When you first take a peek at your disk, it will be covered with all these criss-cross wheel marks. You've just got to keep going until the whole of the disk surface has been pressed. Be patient. It will take about two hours to do properly. You'll get good light transmission but possibly some centre hot spot in your image depending how big an area of the disk image you use for your frame.

If you've get plenty of clear disks to waste with experiments, you could try automotive paint cutting compound in water on a sheet of glass and using it like the aluminium oxide. I don't think it will be graded well enough and there may be odd scratches from large particles.

If you end up with a disk which is too opaque, washing it first to get rid of any pieces of scratchy grit or dirt, then back-polishing it on a piece of flannel cloth will restore some light transmission. You can do this with a sanded disk but the scratches remain and flare in the imag around strong highlights is likely.

Matthew Campbell · February 19th, 2004, 08:30 PM

thanks a lot that is actually a really big help because i wasn't getting the greatest quality picture the other way.
but, can i get some instructions on how to put the entire device together, like i said before maybe it was posted somewhere and i missed it but if someone could explain that or tell me what page that particular peice of info was on i would be much obliged.

Bob Hart · February 20th, 2004, 05:47 AM

Matthew.

If you go back to the beginning of this series there are images to be found of the early versions. Chris the webmaster has also created a condensed version of this thread.

There's a great variety of versions of the Agus. The original and simplest is Agus Casse's version which uses a bulk CD-R disk retail container as an enclosure for the groundglass disk which is a clear spacer from a retail pack of 25 CD-R disks.

An image comes in through a lens on front and appears on a groundglass surface, in his case a clear compact disk made opaque by sanding. This image is upside down and has to be inverted in post or made to appear the right way up by using the camcorder upside down. The image on the disk will be defected by having fixed marks or grain on it. To eliminate this defect the disk is spun so that the image remains constant but the surface texture moves past the image plane faster than the camcorder can resolve it unless high shutter setting are used. To spin it most people have been gutting dead CD players to get a motor and spindle and glueing their disks to the spindle. The voltages applied have been between 1.5v and 9v. I found 3v adequate. There's no rule on this as operating voltages across all the CD player designs are too many to even try to collate. Similar Mabuchi style DC motors can be found in some hobby shops and they are labelled for 1v to 9v.

I have used the term non-inverting Agus35 for this version but there may be other tags for it.

Results from this version can be comparable in quality to the P+S Technik Mini35 with a good SLR lens used and best quality imposed on the dressing of the groundglass CD.

On front is a mount for a SLR 35mm still camera lens of personal choice. The mounts may come from a variety of sources, wrecked cameras or adaptors or a person might make one's own. The still camera lens which I shall call the prime lens has to be positioned so that it is the same distance from the disk as it would be from the film in the SLR camera it came from. This distance can be found by measuring a camera from the mount face of its lens to a O mark with a line through it on top of bottom of the camera, which delineates the focal plane inside the camera (where the film is).

The camcorder sees the image on the disk.

Most camcorders will not be able to see the image on the disk unless some sort of close-up lens or macro lens is used. See Brett Erskines posts on this subject. Various macro lenses suited to individual camcorders maty be used. I have used a telescope eyepiece so that I could get my camcorder within 45mm of the disk image so I could close-couple the Agus for handlholding and general tidyness. The downside is great difficulty in controlling distortion of the image but it can be done. The general workable range of macro lenses seems to be in the region between 7+ to 10+. This places the CD disk image between approx 3" and 5.5" away from the camcorder.

When an erecting version (image right way up version) of the Agus is made using mirrors or prisms in the disk image to camcorder stages, then 4+ to 5+ seems to be ideal macro lens power as the prisms and mirrors add length to the image path while maintaining a short distance between the disk image and the camcorder. The erecting versions are still being developed.

The original CD case version will not lend itself to convenient adaptation to an erecting version. In keeping with the original objective of low cost and absolute simplicity, it is probably not appropriate to want to change this.

Another version which has been made in project boxes or homemade box style enclosures tagged Agus55 will more conveniently facilitate inclusion of an erecting system once it has been sorted.

If you want a quick and acceptable result use the original Agus35 version. If you want something more robust use the Agus55 version. A detailed how-to on this version can be found at

http://ideaspora.net/agus35/

You can find a more or less evolutionary history of my own project in pictures at www.dvinfo.net/media/hart

Start from the earliest dates and you'll get a general idea of where I went with it. The files agus1.jpg to agus3.jpg give an idea of where the prime lens should sit relative to the disk and what the camcorder sees. I have revised the disc motor mount method since this version as posted but have not yet made new pics of it. To enable backfocus adjustment for the prime lens I recommend the motor mount be a flat plate of some kind, fixed to the front of the Agus with three small screws/bolts fastened through into the case then a spring, then the plate, then another nut on the bolt and maybe a locknut on top again although the spring pressure should be enought to lock the first nut. This enables accurate backfocus adjustment.

Bob Hart · February 20th, 2004, 07:06 AM

Furthur to above, I have just received an email from Hiro at Ohara Glass. They are able to supply unfinished cut optical glass disks of 120mm in 1.3mm thickness. These have an opaque finish all over. I am going to handfinish the groundglass finish on the back myself.

I shall have a local optical glass shop which normally does spectacles do the polish on the smooth front face. The accurately centered 15mm holes remain a problem. No one here in WA I have contacted so far can do it. Hiro is looking at getting it accurately done in Japan. This would yield a glass replica of a CD disk.

I am going to order 10 disks. I am probably going to go through one or two before I get mine right. If anyone else is interested in getting some unfinished disks perhaps you might consider posting a note here. On such a small run there won't be any economies of scale but it may be helpful for there to be only one production run of the centreholed unfinished disks. (With Agus Casse's permission they might be called Agusdisks.)

Brett Erskine · February 21st, 2004, 01:35 AM

Bob-
Besides the static ground glass option, you should know that the latest version of the P+S Technik mini35 no longer ROTATES the ground glass because it caused problems with the visual quality of the video. Instead they now rotate the ground glass in place in a small circular motion. That way all of the grain in the ground glass is moving at the same exact speed. Doing it this way also doesnt require you to drill a hole perfectly in the center and makes the overall adapter much much smaller.

-B

John Gaspain · February 21st, 2004, 04:18 AM

ie: the Pro35

Bob Hart · February 21st, 2004, 05:20 AM

Brett.

An orbiting groundglass? - Interesting.

I guess they ran into the same problems we have, ie., run-out of the disk which could be expected to occur in time and use, gyroscopic stress on the groundglass causing momentary soft shifts in backfocus and relay focus when the appliance is agitated. A little movement is very obvious especially in close coupling like my monster.

An orbiting groundglass would be one hell of a lot smaller than our CD-Rs and bullet proof for sudden movements of the camera.

To be any good it would have to have three cranks and a frame around the glass. Slides or rockers would cause an irregular orbit, tendency towards wear and noise. The orbiting groundlgass would need to be in a sealed enclosure or surely there would be a screen-full of faint fuzzy "O's".

For most of us, it may not a convenient option as my understanding of the principle would require at least seven extra parts, all mounted in precise relationship along with some smart dynamic balancing. I'm talking 0.005"? precision or maybe better and that is way out of the hacksaw and gluegun league which is my comfort zone. However the entrails of an orbital sander could show some promise. Come to think of it, the Italian R.U.P.E.S. "Super Stork" sander which was an industry favorite for many years, used a floating platen AND a clever diapragm sleeve fastened by two fine hose clips to replace three or more idler cranks. Alignment was maintained by a very robust crank and 4 x ballbearing set.

C-l-e-v-e-r. I'll wager P+S Technik have gone there. Like the R.U.P.E.S. sander, provided the diaphragm sleeve is not ruptured, no dust gets in, only one single crank is required and the diapragm keeps it relatively quiet.

As you might guess this has been an un-edited stream of consiousness analysis. Two large bottle caps, postage stamp sized groundglass inside one, crankshaft out of model airplane engine, piece of bicycle tube, two hose clamps and you are in business. Actually it would be much more complicated than that and still require engineering level precision to rig.

(So please don't be going out there to rat your little brother's radiocontrol model airplane for the crank out its Supertiger or OS Max engine.)

Ben Gurvich · February 21st, 2004, 10:37 AM

Did Agus ending making that website tutorial.

If so where is it.

Also does te lens have to go up to f1.8

Brett Erskine · February 21st, 2004, 02:01 PM

Bob-
I abandoned the idea early on due to two things: 1) the level of absolute persion needed to create the mounts and mechanics and then properly counter balance such a device. 2)Advances in the quality of ground glass to the point of being able to use it statically.

If you still want to follow my first design I would try and find some piece of equipment out there (like you mentioned) that already has the basic hardware your looking for otherwise you'll be going nutts trying to get it right...even with the right tools.

Good luck.

BTW why are you choosing to still move the ground glass?

Bob Hart · February 21st, 2004, 07:56 PM

Brett.

Why the moving groundglass? I thought fixed groundglass was fine too. So far with my experimentation, a moving groundglass of identical material seems to provide a more uniform image and perhaps a very small superior low light performance.

With our larger disks, the variation between inner and outer surface speeds and the arc angle number across the enture frame is less.

I'm also rolling my own as much as I can and there are ability limits. W.A. is also on the fag end of the just-in-time supply line and some commodities and services have been down-inventoried out of the state. Transport is good however.

For reason of weight, a thin glass disk will run truer than a CD-R. There's also some interesting weird stuff you can do with a 180 degree or 2 x 90 degree paper shutter glued onto the disk and a speed controller on the motor.

I may well come back to the fixed groundglass as the whole thing is a lot more compact but it would require a complete rebuild of what I have done so far.

Brett Erskine · February 21st, 2004, 09:15 PM

Well if you continue you can make a CD run more smoothly by having the outer edge run inside of the groove of outside of bearing.

Bob Hart · February 22nd, 2004, 05:03 AM

Brett.

What type bearing are you referring to? The most compact ballraces I have run into are router tips or salvage out of till scanner mirror or VCR drum motors. Do some of these have an external circlip groove in them. Whichever, it would have to be in good condition otherwise the operating noise would be cruelbad loud with severe loading on any direct drive motor. I'm not too sure how good the glass disks would be in this circumstance. Plastics are largely self lubing but I can see edge spalling and dust being a problem straight up with glass.

Brett Erskine · February 22nd, 2004, 05:14 AM

Try taking a common grease filled bearing found in rollerblades and skateboards and put it into a core that has some type of groove. Mount the bearing to the adapter's housing and your set. If I was going this route I would probably have three or four of these.

Bob Hart · February 23rd, 2004, 07:30 PM

Brett. Thanks for the clue.

Dino Reyes · February 23rd, 2004, 11:04 PM

so i just put together and have a running version of the Agus35 for my xl1s. i had always envisioned it being a little different in design from the original Agus35 in that instead of a 30pack CD spindle, i used a portable CD player and basically cut a 2 inch diameter hole in it and connected via PVC pipe. it's similiar to taking a shotgun and blowing a hole clean through the unit at one corner. i degutted the electronic parts, placed a lcd light on it to make sure i knew if was running if i forgot to turn it off. i picked up a 2 sheets of 5x6 frosted glass (1.7mm thickness) from Edmunds Optical, sanded at roughly 220 grit, for $15 bucks each. i paid a stain glass cutter $10 to cut it into an a perfect shape of a CD (she broke one in her first attempt) and popped it in the CDplayer and it was perfectly balanced. i put two high powered double AA batteries in and it runs whisper quiet, infact so quiet have to check if it's on or not all the time. i didn't put a on/off switch on it as i wanted to test it out. i support it with some 15mm rails i bought for it. as for the image reversing, i just flip the eye viewer and it is right-sided easily. there are just two things i need to improve, one is that the image is still on the darker side, and a bit fuzzy, yellow, halo-ish-as, i believe, the gg is not fine enough, so i am ordering some 600grit aluminum oxide to improve the opticals and the next is getting a slightly wider "relay" lens. the current one i have is a 55mm, nikkor f1.2. i believe it's a little too narrow for what i am doing and i would like to pick up more of the gg image. I am using a 50mm f2 lens for the primary.

Would you reccommend i get a Macro type lens as my Nikkor isn't one, just a standard, and I think that might be a problem. I also have a +10 close-up lens in front of my "relay" lens. I also have a fresnel lens in front of the gg, concentric rings facing the gg. would you think i need to put that after the gg?

i'll also post some nice schematics in the next day or so to show how i did it.

I am also working on a Aldu35 Static verison for the XL1s. But, right now i'm interested in brightening up my image and trying to refine and test. Any thoughts would be appreciated...

-D

February 21st, 2004, 04:18 AM	#966
John Gaspain Major Player Join Date: Oct 2003 Location: WA-USA Posts: 371	ie: the Pro35 __________________ The glory of the World passes by.

February 21st, 2004, 10:37 AM	#968
Ben Gurvich Major Player Join Date: Dec 2003 Location: Australia Posts: 329	Agus Website Did Agus ending making that website tutorial. If so where is it. Also does te lens have to go up to f1.8

February 23rd, 2004, 11:04 PM	#975
Dino Reyes Regular Crew Join Date: Dec 2003 Location: brooklyn Posts: 66	Agus35 for xl1s so i just put together and have a running version of the Agus35 for my xl1s. i had always envisioned it being a little different in design from the original Agus35 in that instead of a 30pack CD spindle, i used a portable CD player and basically cut a 2 inch diameter hole in it and connected via PVC pipe. it's similiar to taking a shotgun and blowing a hole clean through the unit at one corner. i degutted the electronic parts, placed a lcd light on it to make sure i knew if was running if i forgot to turn it off. i picked up a 2 sheets of 5x6 frosted glass (1.7mm thickness) from Edmunds Optical, sanded at roughly 220 grit, for $15 bucks each. i paid a stain glass cutter $10 to cut it into an a perfect shape of a CD (she broke one in her first attempt) and popped it in the CDplayer and it was perfectly balanced. i put two high powered double AA batteries in and it runs whisper quiet, infact so quiet have to check if it's on or not all the time. i didn't put a on/off switch on it as i wanted to test it out. i support it with some 15mm rails i bought for it. as for the image reversing, i just flip the eye viewer and it is right-sided easily. there are just two things i need to improve, one is that the image is still on the darker side, and a bit fuzzy, yellow, halo-ish-as, i believe, the gg is not fine enough, so i am ordering some 600grit aluminum oxide to improve the opticals and the next is getting a slightly wider "relay" lens. the current one i have is a 55mm, nikkor f1.2. i believe it's a little too narrow for what i am doing and i would like to pick up more of the gg image. I am using a 50mm f2 lens for the primary. Would you reccommend i get a Macro type lens as my Nikkor isn't one, just a standard, and I think that might be a problem. I also have a +10 close-up lens in front of my "relay" lens. I also have a fresnel lens in front of the gg, concentric rings facing the gg. would you think i need to put that after the gg? i'll also post some nice schematics in the next day or so to show how i did it. I am also working on a Aldu35 Static verison for the XL1s. But, right now i'm interested in brightening up my image and trying to refine and test. Any thoughts would be appreciated... -D

February 19th, 2004, 05:41 AM	#961
Bob Hart Inner Circle Join Date: Dec 2003 Location: PERTH. W.A. AUSTRALIA. Posts: 4,477	Matthew It's best you don't go near your CD with sandpaper or any other paper for that matter if you are going to rub it across your disk. Okay you will get an opaque surface on one face of the disk but the performance will be less than it need be for the same amount of resources and sweat. You need pits, not scratches on your disk. The best result will be with a fine aluminium oxide powder of 300 grade, mixed with water and rubbing your disk in very very small circles (quarter inch or less if you can do it) on a very clean glass sheet. This is done without pressing on the disk but allowing the powder to do its work by rolling along under the disk and stamping pits in it, not fixing to a lower surface and then drawing long scratches across the disk. It takes a long time as high edges on the disk rim and centre have to be worn down first. The fine powder may not be readily available to you. If you use paper, then anything courser than 600 grade will be a waste of time. Preferably you should place your disk facedown on a clean surface, on a clean piece of thin soft cloth. Place your 600 grade paper face down on your disk. Wet and dry silicon carbide paper is best as pieces are less likely to come off and get on the clear side of your disk and scratch it whilst you work. Hold the paper from moving across the disk and use a hard round ended object about the size of a pen or pencil and scrub this firmly back and forth across the paper to make the grit press pits into the disk surface. You can automate this process a little by finding an old ball bearing race at your local auto shop or wrecker, holding the centre and using the outer race as a roller. Doing it this way will also save premature wear on the back of the wet and dry paper. You'll need to tilt your wheel slightly so high local pressures occur on the paper. Lift your paper off often, move it slghtly and put it on the disk again. Don't allow it to rub. When you first take a peek at your disk, it will be covered with all these criss-cross wheel marks. You've just got to keep going until the whole of the disk surface has been pressed. Be patient. It will take about two hours to do properly. You'll get good light transmission but possibly some centre hot spot in your image depending how big an area of the disk image you use for your frame. If you've get plenty of clear disks to waste with experiments, you could try automotive paint cutting compound in water on a sheet of glass and using it like the aluminium oxide. I don't think it will be graded well enough and there may be odd scratches from large particles. If you end up with a disk which is too opaque, washing it first to get rid of any pieces of scratchy grit or dirt, then back-polishing it on a piece of flannel cloth will restore some light transmission. You can do this with a sanded disk but the scratches remain and flare in the imag around strong highlights is likely.

February 19th, 2004, 08:30 PM	#962
Matthew Campbell Tourist Join Date: Feb 2004 Location: Helena Montana Posts: 2	thanks a lot that is actually a really big help because i wasn't getting the greatest quality picture the other way. but, can i get some instructions on how to put the entire device together, like i said before maybe it was posted somewhere and i missed it but if someone could explain that or tell me what page that particular peice of info was on i would be much obliged.

February 20th, 2004, 05:47 AM	#963
Bob Hart Inner Circle Join Date: Dec 2003 Location: PERTH. W.A. AUSTRALIA. Posts: 4,477	Matthew. If you go back to the beginning of this series there are images to be found of the early versions. Chris the webmaster has also created a condensed version of this thread. There's a great variety of versions of the Agus. The original and simplest is Agus Casse's version which uses a bulk CD-R disk retail container as an enclosure for the groundglass disk which is a clear spacer from a retail pack of 25 CD-R disks. An image comes in through a lens on front and appears on a groundglass surface, in his case a clear compact disk made opaque by sanding. This image is upside down and has to be inverted in post or made to appear the right way up by using the camcorder upside down. The image on the disk will be defected by having fixed marks or grain on it. To eliminate this defect the disk is spun so that the image remains constant but the surface texture moves past the image plane faster than the camcorder can resolve it unless high shutter setting are used. To spin it most people have been gutting dead CD players to get a motor and spindle and glueing their disks to the spindle. The voltages applied have been between 1.5v and 9v. I found 3v adequate. There's no rule on this as operating voltages across all the CD player designs are too many to even try to collate. Similar Mabuchi style DC motors can be found in some hobby shops and they are labelled for 1v to 9v. I have used the term non-inverting Agus35 for this version but there may be other tags for it. Results from this version can be comparable in quality to the P+S Technik Mini35 with a good SLR lens used and best quality imposed on the dressing of the groundglass CD. On front is a mount for a SLR 35mm still camera lens of personal choice. The mounts may come from a variety of sources, wrecked cameras or adaptors or a person might make one's own. The still camera lens which I shall call the prime lens has to be positioned so that it is the same distance from the disk as it would be from the film in the SLR camera it came from. This distance can be found by measuring a camera from the mount face of its lens to a O mark with a line through it on top of bottom of the camera, which delineates the focal plane inside the camera (where the film is). The camcorder sees the image on the disk. Most camcorders will not be able to see the image on the disk unless some sort of close-up lens or macro lens is used. See Brett Erskines posts on this subject. Various macro lenses suited to individual camcorders maty be used. I have used a telescope eyepiece so that I could get my camcorder within 45mm of the disk image so I could close-couple the Agus for handlholding and general tidyness. The downside is great difficulty in controlling distortion of the image but it can be done. The general workable range of macro lenses seems to be in the region between 7+ to 10+. This places the CD disk image between approx 3" and 5.5" away from the camcorder. When an erecting version (image right way up version) of the Agus is made using mirrors or prisms in the disk image to camcorder stages, then 4+ to 5+ seems to be ideal macro lens power as the prisms and mirrors add length to the image path while maintaining a short distance between the disk image and the camcorder. The erecting versions are still being developed. The original CD case version will not lend itself to convenient adaptation to an erecting version. In keeping with the original objective of low cost and absolute simplicity, it is probably not appropriate to want to change this. Another version which has been made in project boxes or homemade box style enclosures tagged Agus55 will more conveniently facilitate inclusion of an erecting system once it has been sorted. If you want a quick and acceptable result use the original Agus35 version. If you want something more robust use the Agus55 version. A detailed how-to on this version can be found at http://ideaspora.net/agus35/ You can find a more or less evolutionary history of my own project in pictures at www.dvinfo.net/media/hart Start from the earliest dates and you'll get a general idea of where I went with it. The files agus1.jpg to agus3.jpg give an idea of where the prime lens should sit relative to the disk and what the camcorder sees. I have revised the disc motor mount method since this version as posted but have not yet made new pics of it. To enable backfocus adjustment for the prime lens I recommend the motor mount be a flat plate of some kind, fixed to the front of the Agus with three small screws/bolts fastened through into the case then a spring, then the plate, then another nut on the bolt and maybe a locknut on top again although the spring pressure should be enought to lock the first nut. This enables accurate backfocus adjustment.

February 20th, 2004, 07:06 AM	#964
Bob Hart Inner Circle Join Date: Dec 2003 Location: PERTH. W.A. AUSTRALIA. Posts: 4,477	Furthur to above, I have just received an email from Hiro at Ohara Glass. They are able to supply unfinished cut optical glass disks of 120mm in 1.3mm thickness. These have an opaque finish all over. I am going to handfinish the groundglass finish on the back myself. I shall have a local optical glass shop which normally does spectacles do the polish on the smooth front face. The accurately centered 15mm holes remain a problem. No one here in WA I have contacted so far can do it. Hiro is looking at getting it accurately done in Japan. This would yield a glass replica of a CD disk. I am going to order 10 disks. I am probably going to go through one or two before I get mine right. If anyone else is interested in getting some unfinished disks perhaps you might consider posting a note here. On such a small run there won't be any economies of scale but it may be helpful for there to be only one production run of the centreholed unfinished disks. (With Agus Casse's permission they might be called Agusdisks.)

February 21st, 2004, 01:35 AM	#965
Brett Erskine Major Player Join Date: Dec 2003 Location: Anaheim, CA Posts: 445	Bob- Besides the static ground glass option, you should know that the latest version of the P+S Technik mini35 no longer ROTATES the ground glass because it caused problems with the visual quality of the video. Instead they now rotate the ground glass in place in a small circular motion. That way all of the grain in the ground glass is moving at the same exact speed. Doing it this way also doesnt require you to drill a hole perfectly in the center and makes the overall adapter much much smaller. -B

February 21st, 2004, 05:20 AM	#967
Bob Hart Inner Circle Join Date: Dec 2003 Location: PERTH. W.A. AUSTRALIA. Posts: 4,477	Brett. An orbiting groundglass? - Interesting. I guess they ran into the same problems we have, ie., run-out of the disk which could be expected to occur in time and use, gyroscopic stress on the groundglass causing momentary soft shifts in backfocus and relay focus when the appliance is agitated. A little movement is very obvious especially in close coupling like my monster. An orbiting groundglass would be one hell of a lot smaller than our CD-Rs and bullet proof for sudden movements of the camera. To be any good it would have to have three cranks and a frame around the glass. Slides or rockers would cause an irregular orbit, tendency towards wear and noise. The orbiting groundlgass would need to be in a sealed enclosure or surely there would be a screen-full of faint fuzzy "O's". For most of us, it may not a convenient option as my understanding of the principle would require at least seven extra parts, all mounted in precise relationship along with some smart dynamic balancing. I'm talking 0.005"? precision or maybe better and that is way out of the hacksaw and gluegun league which is my comfort zone. However the entrails of an orbital sander could show some promise. Come to think of it, the Italian R.U.P.E.S. "Super Stork" sander which was an industry favorite for many years, used a floating platen AND a clever diapragm sleeve fastened by two fine hose clips to replace three or more idler cranks. Alignment was maintained by a very robust crank and 4 x ballbearing set. C-l-e-v-e-r. I'll wager P+S Technik have gone there. Like the R.U.P.E.S. sander, provided the diaphragm sleeve is not ruptured, no dust gets in, only one single crank is required and the diapragm keeps it relatively quiet. As you might guess this has been an un-edited stream of consiousness analysis. Two large bottle caps, postage stamp sized groundglass inside one, crankshaft out of model airplane engine, piece of bicycle tube, two hose clamps and you are in business. Actually it would be much more complicated than that and still require engineering level precision to rig. (So please don't be going out there to rat your little brother's radiocontrol model airplane for the crank out its Supertiger or OS Max engine.)

February 21st, 2004, 02:01 PM	#969
Brett Erskine Major Player Join Date: Dec 2003 Location: Anaheim, CA Posts: 445	Bob- I abandoned the idea early on due to two things: 1) the level of absolute persion needed to create the mounts and mechanics and then properly counter balance such a device. 2)Advances in the quality of ground glass to the point of being able to use it statically. If you still want to follow my first design I would try and find some piece of equipment out there (like you mentioned) that already has the basic hardware your looking for otherwise you'll be going nutts trying to get it right...even with the right tools. Good luck. BTW why are you choosing to still move the ground glass?

February 21st, 2004, 07:56 PM	#970
Bob Hart Inner Circle Join Date: Dec 2003 Location: PERTH. W.A. AUSTRALIA. Posts: 4,477	Brett. Why the moving groundglass? I thought fixed groundglass was fine too. So far with my experimentation, a moving groundglass of identical material seems to provide a more uniform image and perhaps a very small superior low light performance. With our larger disks, the variation between inner and outer surface speeds and the arc angle number across the enture frame is less. I'm also rolling my own as much as I can and there are ability limits. W.A. is also on the fag end of the just-in-time supply line and some commodities and services have been down-inventoried out of the state. Transport is good however. For reason of weight, a thin glass disk will run truer than a CD-R. There's also some interesting weird stuff you can do with a 180 degree or 2 x 90 degree paper shutter glued onto the disk and a speed controller on the motor. I may well come back to the fixed groundglass as the whole thing is a lot more compact but it would require a complete rebuild of what I have done so far.

February 21st, 2004, 09:15 PM	#971
Brett Erskine Major Player Join Date: Dec 2003 Location: Anaheim, CA Posts: 445	Well if you continue you can make a CD run more smoothly by having the outer edge run inside of the groove of outside of bearing.

February 22nd, 2004, 05:03 AM	#972
Bob Hart Inner Circle Join Date: Dec 2003 Location: PERTH. W.A. AUSTRALIA. Posts: 4,477	Brett. What type bearing are you referring to? The most compact ballraces I have run into are router tips or salvage out of till scanner mirror or VCR drum motors. Do some of these have an external circlip groove in them. Whichever, it would have to be in good condition otherwise the operating noise would be cruelbad loud with severe loading on any direct drive motor. I'm not too sure how good the glass disks would be in this circumstance. Plastics are largely self lubing but I can see edge spalling and dust being a problem straight up with glass.

February 22nd, 2004, 05:14 AM	#973
Brett Erskine Major Player Join Date: Dec 2003 Location: Anaheim, CA Posts: 445	Try taking a common grease filled bearing found in rollerblades and skateboards and put it into a core that has some type of groove. Mount the bearing to the adapter's housing and your set. If I was going this route I would probably have three or four of these.

February 23rd, 2004, 07:30 PM	#974
Bob Hart Inner Circle Join Date: Dec 2003 Location: PERTH. W.A. AUSTRALIA. Posts: 4,477	Brett. Thanks for the clue.