Mini35 Oscillating Ground Glass Idea

[Dan Miller]

Has anybody tried to incorporate an oscillating motor into their homemade mini35's to move the ground glass? I was at an arcade the other day and saw a ticket game called Big Haul that gave me this idea.

Here is a crude depiction (500 Kb animated gif) that demonstrates what I saw... the arm connected to the ground glass and the arm connected to the motor would have to be shorter in length in order to restrict the ground glass from moving so far to each side.

http://www.geocities.com/millertiller12/GG.gif

I have no idea if the 400 series mini35 oscillates the ground glass in this fashion or if this will even work.

[Rai Orz]

Dan: Server not found at: http://us.f2.yahoofs.com/bc/40c66bf9_40cb/bc/My+Documents/GG.gif?bfz8oxABWpLLNYwF

But:
I build a working oscillating 35mm adapter. It will works also with a HDTV Cam because you can´t see any grid. (Excuse my bad English) After very long time, test different construction units and constant new calculation, now it works:
First i used the finest GG i found (with no motion the grid must very, very fine!!! See with HDTV but only a little see with a standard cam). Then the GG is mounted on a plate. This plate is fastened at 3 points with spezial rubber bolts, that allowed mouvement only left and right, NOT!! up and down. On this plate is a motor, like a CD-ROM Motor, with a very low imbalance. With power on, the motor, the plate and the GG is oscillating 3 to 5 times more that the very fine grid. (This oscillating makes an very little circle). You can´t see with your eyes that oscillating, but the gid is never see with the camara. The vibration is very small and kill together with any sounds by using another 3point rubber bolts. This last one is also used to adjust the GG distance to the lens. The whole thing is small and very insensitive in relation to outside vibrations or movements.
Possibly I will arrange a self made kit or will sell the complete equipment. See times

[Dan Miller]

Sorry, try this link:

http://www.geocities.com/millertiller12/GG.gif

[Obin Olson]

Rai, I have a HDTV camera I am building can you send me info for the GG you made right away? I want to try it with HDTV

[Brett Erskine]

Find something no more than a 1/2 inch long that can hold two mini bearings side by side and I'll post a picture of a design that works just like the Mini35 400 series. Its the only thing I havent been able to find.

-Brett Erskine

[Dan Miller]

Brett,

When you say find something no more than a 1/2 inch long... I assume you mean an arm or an extension right?

[Rai Orz]

Obin: Next week i have some web space and i will upload more information about my adapter.

Brett: Do you know in details like the original adapter works? how large is the oscillation (in mm)? Which frequency? Can you post the picture, becouse I have my own finemechanical and electronic workshop, so everything is possible...

[Mike Metken]

Dan,

You need to make the travel as short as possible and the oscialtions or vibrations as quick as possible. The short travel is necessary becuse it is easier to keep the distance from the lens constant. The quick movement change is needed because you don't want this thing to be staionary at the end positions too long.

I suggest that you attach the motor at the top of the ground glass, not in the middle of the arm. It would also help in keeping the distance to the lens constant. If you need some help with the design, you can email me directly.

Mike

[Dan Miller]

Mike,

It did occur to me to connect the oscillating arm from the spinning motor directly to the ground glass as you mentioned. As in this example:
http://www.geocities.com/millertiller12/OscGG2.gif

[Brett Erskine]

Yes. The Mini35 series 400 oscillates a round piece of ground glass in a very tight circular motion. To clarify this is a oscillating motion which is different then spining or rotating the GG. I've seen the system first hand but I dont have exact specs when it comes to measurements but if asked to give a estimate I would say the GG was about 55mm in diameter and the oscillations moved the glass in a circular path no larger than 5mm in diameter. The speed, by eye, wasn't too fast as to create a blur but near to it. For example you wouldnt be able to count the rotations by eye. Of coarse that is at the highest speed setting. The Mini35 is adjustable in speed (more or less apparent grain).

As far as the part I was referring to in a previous post- Yes a arm with one bearing on both sides will work. You will need at least three of these arms all together in order to make a perfect oscillating movement. When I get a chance I'll draw up my design and post it. The design is basic in concept but will need to be made with precision and its important that it finely tuned to be counterweighted as to not add any subtle shake to the footage - let alone noise. Many people may end up making oscillating designs not only for their adapters to be grainless but also because builders of the static version are finding it impractical to keep the GG surface PERFECTLY clean. Because if you dont anything and everything - no matter how small - shows up in your footage.

-Brett Erskine

[Mike Metken]

Hey guys,

Circular motion is the best. I heard that Pro 35 claims to have an elipsoid movement. They have some patent on that unit. The Mini 35 has no patents as far as I know.

A circular motion would mean that there would not be any time when the adapter is stationary. Problem are vibrations and Pro 35 has variable speed mainly to prevent vibrations / oscialtions of the lens.

You could have another identical drive on the top. The two drives would work in mechanical or elecronic sync.

There woiuld be no pivot, just sime kind of sliding mechanism to hold the GG from moving back and forth.

You could also have one drive only, connected to the GG at one end with an arm and you would fix the middle of the arm with a pin and the arm would have a slot about a fraction of an inch long with the pin inside. Then the glass would then make the same circular motion as the pin on the drive.

Mike

[Obin Olson]

thank you Rai

[Dietmar Zonewicz]

Not the PRO35 or the mini35 are patented, it is the principle which is patented, so every design with a moving groundglass is covered by this patent.

For the german speaking guys between the community I found the patent (you have to search for the patent):
http://de.espacenet.com/
Beschreibung: Videokamera-Einheit
Veröffentlichungsnumme r : DE10164138 A
Veröffentlichungsdatum : 2002-10-24
Erfinder : WEIGEL WOLFGANG (DE)
Anmelder : P & S TECHNIK GMBH (DE)
Aktenzeichen:
(EPIDOS-INPADOC-normiert) DE20011064138 20011230

I also found a description how the PRO35 works, including a very informative graphic, but I actually don't know where I have it, at home or at work.

The oscillating is very minimal, I barely could't see the movement of the groundglass at the Pro35, so I guess it is less than 0,1mm that the groundglass moves.

dietmar

[Mike Metken]

The patent is from 2002. It only covers the Pro 35. There are no patents on the Mini 35. That overall principle is not covered. Because the overall principle is not covered, you have many ways to go without infringing on the Pro 35 patent. P+S cannot patent the overall principle because a product was already introduced that is using this overall principle and is not patented.

Why was not the Mini 35 principle patented? Because it was not patentable; the principle existed in other products already and was not originally patented or the original patent expired.

I wander what does that 2002 patent cover, and if it is even enforcable.

Mike

[Valeriu Campan]

Don't forget that both Mini35 an Pro35 use a smaller GG that covers the area of 35mm motion picture film, about half of the stills camera. Diffferent issues regarding vibration and DOF and FOV also.