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Old July 20th, 2004, 10:27 PM   #121
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GG demos and how to spot useless ones

Jesse,
I am sorry that you wasted your money on some of the other GG attempts.
Let me just say something about evaluating them:

1) Posting still images of a GG video is WORTHLESS for evaluating the grain. Period. You need to see a slow panning shot of the GG in use, preferably with some of the scene out of focus a bit and shadows and highlights. Only then do you have a chance to see the grain pattern because it remains in the same place on your monitor while the image moves past it.
So you shouldn't ask for frame grabs of the GG for evaluating it for grain.

2) Posting tiny video of some highly compressed format is also worthless for seeing grain effects. The first thing that a compression codec throws away is the grain pattern! The poster should use a 7 megabit mpeg4 or Media9 video to show the details. Then you can see possible fixed pattern grain effects.

OK,
Having said that, how about I post a small demo video, at a high bit rate Media9 ? My camera is an HD-10 JVC, if it works for that, it will work for DV res. no problem. The HD video will be 1280 X 720 pixels. I can also crop into it and make a smaller version for playback on slower computers. I'm open to suggestions on what to do for the Mac. I hear they play media9 now, but with some difficulty.
So, isn't the proof in the pudding, as they say? ( when the pudding is properly compressed )

-Les
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Old July 20th, 2004, 10:30 PM   #122
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Jesse: I understand exactly where you're coming from. Although you don't see many posts from me, I have been following developments and have spent money on glass, aluminum oxide, wax, etc... only to discover a couple of days and few posts later that there's a better way to do something.

HOWEVER, Les does have an actual device (not just something on paper), and I think the price he's asking is easily justifiable for the parts and labor involved, even if it's not in a housing. I don't see a reason why a 5 micron ground glass mounted on a rotating device would not work. However, I am building my own since it is just fun.

Les, have you tried advertising this on other forums where there are less technically minded people? (ie. consumer type people) Well, I don't mean that in a bad way. I just mean...people that don't like to build these things themselves, since that is what a majority of us guys in this thread are, I think.
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Old July 21st, 2004, 12:09 AM   #123
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Les-

A video clip would be great. I can handle high-res.
Also how big is the target area? Is the vibration isolated in the adapter? Does it shake the camera at all?

thanks
-jes
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Old July 21st, 2004, 12:33 AM   #124
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The cutout size right now is about 42mm X 30mm, but I want to switch to a 4 shaft system that will leave a little larger area. Right now the hole is not centered top to bottom either, another reason I want to change the design. The motor seems to run fine on 6V , four AA batteries are adequate.

There is a small amount of vibration, it's impossible to get rid of it all. I'm going to soft mount it in the housing, to minimize external vibrations. This must be done in such a way to avoid any z axis motion, which would ruin focus.
I haven't attempted to advertise anywhere, as this is really more for the type of person that can adapt it to their own use. It would not ship with a GG, for legal reasons.
I'll try to make some demo video in the next few days.
-Les
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Old July 21st, 2004, 01:45 AM   #125
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Les do we all get royalties for our contributions? ;-)

Im only kidding. Good luck.

-Brett Erskine
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Old July 21st, 2004, 02:33 AM   #126
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my roller ball
I will try to get more of them.
http://www.giroud.com/minidv/roller.jpg
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Old July 22nd, 2004, 03:05 AM   #127
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Where did you pick up your bearings/pulley wheel?
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Old July 22nd, 2004, 07:26 AM   #128
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frankly , i do not know.
i got a friend who got a box full of this, a few month ago, a take five of them to see if they could fit my needs for my video crane.
since the crane is going to a no-cable version, i will probably use these little marvels to the vibrating gg project.
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Old July 24th, 2004, 02:14 PM   #129
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Les,

How's that video clip coming? I'm anxious to see it.
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Old July 24th, 2004, 03:12 PM   #130
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It's finally the weekend, I'll get a chance to work on it!

-Les

<<<-- Originally posted by Jesse Rosten : Les,

How's that video clip coming? I'm anxious to see it. -->>>
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Old July 26th, 2004, 01:56 AM   #131
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Update: I tested with a lens and GG and discovered a very slight ( about 0.0015 inch ) off axis motion that causes the image to move laterally a little. I think one of the shafts is off center, I have to take it all apart and check, I'll probably make a new backing plate for the bearings. This thing has to be very precise for sure to get a good image. Also, I think that a fairly slow rpm will work, the grain moves by fairly fast with my 1.5mm radius.

So no video clip yet.
-Les
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Old July 26th, 2004, 09:48 AM   #132
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Les.

If your device is floating on rubber mounts, you may find you need counterbalance on either side of load centerpoint on each shaft, not just one side, otherwise the counterweights themselves may be creating the abberant motion you describe. It may not be a shaft running out.

Depending on how much of the oscillating mass you manage to balance out you will still get vibration but it will occur directly and not obliquely across the image axis. Make sure wires and other attachments come off at the load centre as well.

If your device is rigidly mounted, then you may have clearance in the bearings being taken up, again by the same offset counterbalance problem.

I am assuming that the bearings are a secure fit on their shafts and crankpins and the housings they fit into and cannot float. If not then you will need to limit movement along the image axis with some sort of guide frame. If this is already part of the design then ignore this commentary.

Don't take my ramblings too seriously as I am not an engineer. I do know that small 2 stroke engines with a half-crankshaft (like the oscillating groundglass devices) vibrate cruel-bad compared to a full crankshaft version of the same power and cubic capacity.
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Old August 1st, 2004, 11:38 PM   #133
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Les -

I'm still interested in your oscillator. If I disappear for the next three weeks it's because I'll be on location in Africa <plug plug> :)

peace
jes
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Old August 2nd, 2004, 02:59 AM   #134
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Jesse,
I worked on it a bit this weekend. It still has some Z axis deflection that I'm trying to minimize. I can test it by looking at the mirror reflection of the GG shiny side, at a grazing angle. Even the smallest deflection, under 0.001 inch is enough to move the image around, indication that there is some Z axis motion. I'm thinking one of my eccentric shafts is off, I think I'm going to remake them, out of brass this time ( easier to machine ).

I want to post some tests soon. HD is very demanding, I don't want to diminish it's sharpness with my DOF adapter!

Africa... be safe, it's rather lawless in many places!

-Les
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Old August 2nd, 2004, 03:13 AM   #135
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<<<-- Originally posted by Les Dit : Jesse,
. I can test it by looking at the mirror reflection of the GG shiny side, at a grazing angle. Even the smallest deflection, under 0.001 inch is enough to move the image around, indication that there is some Z axis motion.
-Les -->>>
Les,
Try to use a small laser pointer and look at the reflection on a screen or surface away from the disk. The "amplification factor" will make the measurement of the deflection easier.
Good luck
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