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Old August 4th, 2004, 03:17 PM   #1
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Image Flipping on the Agus 35

I built my version of this ingenious adapter last Winter (with the generous help of the DVI community and a friend's father), and the result has been amazing. However, due to the challenge of shooting through a viewfinder that's flipped horizontally and vertically, I've been slow to implement the Agus 35 adapter into any of my projects.

As far as utilizing a pentaprism or a complex set of mirrors, I'd like to keep the light path as short as possible. The Olympus 50mm lens, fresnel, pre-frosted cd, and +10 macro already cut out a stop or two, which doesn't help much on a GL1! I'm also opposed to a complex rig where the camera is flipped upside down, it'd make handling the camera even tougher than it already is with this contraption strapped to it.

What I'm proposing - and I'm quite sure someone else has probably already tried this - using a hoodman type housing over the LCD screen with a mirror inside at a 45 degree angle. In theory - and in my head - this should work like a charm. Just wondering if anyone else has had success with such a rig. I've posted pics of my set-up below, since I always like to check out other people's rigs! Thanks for your help!

http://www.par-t-com.net/mini50_guts.JPG
http://www.par-t-com.net/mini50_wide.JPG
http://www.par-t-com.net/mini50_front.JPG

PS - any ideas on how to dampen the hum that the motor generates?
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Old August 4th, 2004, 03:29 PM   #2
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If the motor is inside the box sound-proofing the box might help
a bit? Otherwise it is probably best to hunt for another motor.
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Old August 4th, 2004, 04:13 PM   #3
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Devin Doyle

There is two option for this,

First one here is I use a wide angle ,cheap one (Ambico V-0310 Fish eye)Whit a prism on top of it that flip the image.
http://www.kheops-tech.com/~ad3d/Aldufinal.jpg

The other way is to make a little modification to the camera
Is is a discution about this
http://www.dvinfo.net/conf/showthread.php?s=&threadid=23982

Alain
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Old August 4th, 2004, 05:58 PM   #4
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Rob - The motor is installed on the inside of the box, I was wondering if anyone was using a specific material to sound-proof the interior to dampen the low hum. It's a cd player motor, so it isn't too loud.

Alain - Thanks for those links, they were helpful. Unfortunately I can't find the "sweet spot" on my GL1 with a magnet; although that is a neat little mod.

Thanks to both of you guys for contributing. Does anyone else have a method that hasn't been discussed?
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Old August 4th, 2004, 09:14 PM   #5
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Re: Motor Hum.

What RPM or voltage are you using?

My experience is that if the camcorder shutter speed is kept down to 1/50th of a sec and if the groundglass is fine enough and most importantly consistent right around the circle, 1.5v or about 1500rpm is adequate to dissolve the grain.

Flickering seems to come about when a larger more subtle defect strobes past the camcorder view. An oily fingerprint on the groundglass side of the disk is enough to do it.

On the plumbers version I had space enough to make the three mount points 70mm from the hub center which gives the mount plate enough flexibility to deaden some of the vibration and for the disk to self-align to some degree. The material I have settled on is polypropolene sheet of 3mm thickness which is not as acoustically live as some other plastics, metals or wood.

I also use silicone bathroom sealant (water cleanup) to mount the disk to the hub. If you get it wrong you can wedge the disk off the hub with a fine blade out of a disposable shaver. To help the alignment, I mount the motor firmly with the disk in a flat position and run it a high speed before the initial set occurs in the adhesive. The disk tends to straighten by gyro forces. About a minute is sufficient. The glue sets and the disk is effectively self-aligned.

I was going to use rubber grommets on the three bolts however found I did not need them.

I am back-engineering my rough prototype and can provide you with .tcw or .pdf files of the method.
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Old August 5th, 2004, 08:53 AM   #6
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Bob - Thanks for your advice. I'm currently running 2 AAA batteries. So total should be 1.5 v, correct? At any rate, the hum isn't that bad, but it would interfere with audio. I'll crack open my mini-50 and try to pinpoint the source of the vibration/noise again, although I've been unsuccessful thus far. I suppose I could focus on that, as well as lining the interior with a sound-deadening material. I'm opposed to glueing (sp?) the pre-frosted cd to the motor itself, as I may want to change it if (heaven forbid) something were to happen to it. Have you - or anyone for that matter - played around with image inversion so it displays right side up? Anyone specifically on finding the "sweet spot" on the GL1? Thanks for your help!
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Old August 6th, 2004, 06:49 AM   #7
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If the batteries are connected in parallel (battery number one's + to to battery number two's + and battery number one's - to battery number two's - , then connected from these common points to load) you get 1.5 volts.

If the batteries are connected in series (battery number one's + to load, battery number one's - to battery number two's + and battery number two's - to load), you get 3 volts.

For 1.5v with a Mabuchi style (tin can) motor common to many CD player decks as disk spindle drive, (long shaft)or lazer head transport/disk tray actuator motors, (short shaft), you get approximately 1500rpm. You get approximately 3000rpm for 3v. These motors can also be found unmounted in some hobby stores but of course you don't get a plastic CD spindle with them.

My personal preference was to use the short shaft motors. Their tasking is intermittent and they are likely to be less worn.

The plastic spindle can be persuaded to slip off the motor shaft but must be pressed off by the small shoulder which ends on the shaft closest to the motor case. If you try to pull it off by the disk shoulder itself, it may come away partially without breaking but then the small shoulder will snap off. All is not lost as you can still use it but it may no longer run true.

I mounted a broken one onto a short shaft motor because of space constraints within the housing I built. This allowed me to place the disk closer to the motor case. This reduces any out of balance effects as the disk mass is closer to the mounting point of the motor.

The Mabuchi style motors provide for mounting by the face closest to the disk mount. This arrangement should be used as it also keeps the disk mass closest to the mounting and reduces its leverage over the structure, therefore less vibration.

The motors have tags on the back which appear to mount the motor into a printed circuit board. This is a design decision to facilitate easy fastening of the board in mass production, not the motor. The tags are not intended to be a dynamic load bearing element.

Take care when fastening the motor using the original screws to a new mounting. The screws can go through into the armature inside and ruin the windings. Screw gently in and rotate the shaft whilst you do this. Any hint of binding of the armature and you should back off and use washers to space the screws out.

As for fastening the disk to the hub, if you use the whole of the CD player disk drive (hub and pressure plate, you need not worry about glue.

As for image inversion, I have built a prismatic erecting version of the Agus to bring the image into the cam upright but it is not an overwhelming success so far, mainly because I have had to go back to my stack of three Hoya close-up lenses which cause rainbow effect, soft focus on the edges and radial distortion in the image. The prism path seems to aggravate this effect though the prisms themselves don't seem to produce any rainbow effect of their own so far.
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Old August 6th, 2004, 02:28 PM   #8
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Any news on flipping the image inside the Agus/Aldu-system by the means of optical elements, or even completely different workarounds?
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Old August 7th, 2004, 12:33 AM   #9
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I have tried but not yet achieved the same image quality as the non-erecting version, mainly becaus I have had to use an older relay lens system which was not as good.

Getting the image upright is relatively easy but for the untrained engineer, the precision required is at, possibly beyond the ability limit.

Instead of working along a single common centerline you are now working with three.

I published a conceptual side view as a .pdf file on www.dvinfo.net/media/hart but don't try to build to it as it is wrong by 10mm due to a misread of a measuring instrument.
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