Mini35 Oscillating Ground Glass Idea

[Brett Erskine]

Thanks for the comment on my demo reel. I dont want to talk off subject too long so I'll make this quick.

Shot on 16mm, Two 2k fresnel bounced into 2 3'X3' foam core, dark smoke colored backdrop, fake snow, 1 girlfriend, 45 fps, heavily overexposed, color shift during telecine, slight highlight glow ala Photoshop.

Half of that demo was shot on the DVX100 and the other two "travel epics" demos were COMPLETELY shot on the DVX100. Amazing camera.

For thoughs interested heres a link to the demos:

www.CinematographerReels.com

-Brett Erskine

Back to the subject - I decided to just take to finely threaded metric bolts and have them spot welded side by side at the tip. Its seems like its going to work well because I can just screw on all of the hardware I need on to it and everything will be rock solid. I'll post pics soon if someone is interested.

Thanks for the info about the audio motors. I may end up going that way but before I do I really want to look into these ultrasonics. I found some small ones but they are AC or only 250 rpm. Havent found any advertised prices...Im starting to think that these little guys are expensive. Anyone else doing research on them?

[Les Dit]

I'm thinking of building a run of parts kits for the oscillating substrate mover. It would be similar looking to the one I posted pictures of before, but with 4 shafts. It would include the motor and mount for the motor. It will be matte black. You provide your own center piece to orbit. The mount will have a hole for it.

It took me about 6+ hours of work to make the first one, but if I do several at the same time, it would make it easier.
I'm thinking $375 for the 4 shaft version, if I get several people interested.
I'm just putting a 'feeler' out there at this time, to see if it's at all interesting to those DOF fans out there.

-Les

[Brett Erskine]

Les-
What city are you from? I'm from Anahiem, CA. Maybe we should work together on our adapters.

-Brett Erskine

[Matthew Miller]

I suppose I'm gonna have to read this thread more carefully to really understand how this device rotates/oscillates/does-its-thing.
Les,
I'm wondering what modifications might need to take place to use a Medium Format lens, which projects an image twice as large as a 35mm lens projects onto the GG. Major Reworking of the design, or just cut a bigger hole and space it all farther out?

[Les Dit]

Matthew, these pictures shows the basic device I made:
( see the dsc named pics )
http://home.earthlink.net/~lesd/hd/

I do plan on making the next one bigger and with 4 shafts to allow more optimum use of the middle area. Using a larger area even with a 35mm derived lens would be a plus.

-Les

[Filip Kovcin]

i was in the hobby shop last friday, and discovered very powerfull (and expencive - about 200$ (at least in poland) ) brushless motor with all cabling etc. - for remote controled model airplanes, cars etc. which can acheive more than 20.000 rpm. and is very quiet. does anyone of you know more about these things?

motor is in my opinion proper in size and if you use lower voltage - it revolves slower. (it starts from 750rpm and each 1v added is 750rpm more)

i understand that for our purpose - we will need minimum 1800 rpm (ntsc) or 1500 rpm for pal countries. yes?

does anyone knows what manufacturer made p+s motor?

================
to les dit:

i'm impressed! great work! what kind of motor you are using with your device?


thanks,

filip

[Les Dit]

Thanks!
I used a motor from a tape recorder.
The motors from the hobby shop you mentioned are high amperage high power for cars and planes. The motor I use only draws about 1/3 amp at 6V , you don't need much power.
The speed depends on the shutter speed as well as the radius of movement.
-Les



<<<-- Originally posted by Filip Kovcin : i was in the hobby shop last friday, and discovered very powerfull (and expencive - about 200$ (at least in poland) ) brushless motor with all cabling etc. - for remote controled model airplanes, cars etc. which can acheive more than 20.000 rpm. and is very quiet. does anyone of you know more about these things?

motor is in my opinion proper in size and if you use lower voltage - it revolves slower. (it starts from 750rpm and each 1v added is 750rpm more)

i understand that for our purpose - we will need minimum 1800 rpm (ntsc) or 1500 rpm for pal countries. yes?

does anyone knows what manufacturer made p+s motor?

================
to les dit:

i'm impressed! great work! what kind of motor you are using with your device?


thanks,

filip -->>>

[Brett Erskine]

Im going with medium format GG because its at least 4X as large (surface area). Contrast, sharpness are greatly increased and grain reduced. I plan on using medium format lenses once in a while but the beauty of having over sized GG is that you can choose between different format lenses. Want to use a 35mm lens - fine, a medium format lens - fine too. Thru test I found that 35mm lens already throw a image nearly the size of 2 1/4 medium format GG so this means even if you stick with 35mm lenses you'll see a fairly large improvement in contrast, sharpness and grain. ANOTHER plus to using medium format GG is you dont have to zoom in as much with your camcorder's lens and you know what that means...You can use a faster f stop on your camcorders lens which is VERY important for a homemade mini35. AND since you dont have to zoom in any more that also means that you dont need to use expensive achromatic diopters.

Im having a custom GG made by a specialist. He really seems to know what he's doing and he claims its the brightest, least grain, most even field GG out there. Well see. I'll let you all know.

So Les how do you like the tape recorder motors? Are you picking up their noise in your mics? Are they fast enough to get rid of the grain...even at 1/500 shutter speed? Are you going to keep them for your next version of the adapter or would you change anything about them if you could?

See ya
-Brett Erskine

[Brett Erskine]

I should mention one BAD thing about using larger (medium fomat) GG. Chances are you'll end up with a adapter that is a hair too large and heavy to safely screw mount to the video cameras lens without the aid of a rod support system. Just something to keep in mind when building.

-Brett Erskine

[Frank Ladner]

Brett: Your idea sounds excellent! However, if you do decide to switch down from medium format to 35mm lenses, you would need to use an achromat and/or zoom, right? (Due to the smaller projected image.) Or did I miss something?

Thanks!

[Giroud Francois]

frankly whatever is the size or weigth or your adapter, i would not recommend using it without some support , without the risk of seeing the front of your camera popping out .
additionally using the upside down camera is a good idea that require some additional mount anyway.
if i got time i will show you some pics of my aluminium mount, it is ugly but very efficient.

[Les Dit]

I agree with Giroud,
The screw mounts on camcorders are very weak, usual held together with plastic components.
If you are serious about going to the effort of mimicking 35mm DOF, you should be thinking of a rail mount system for the DOF maker and the filter holder as well as shade system on the front of that.
Be careful of that little screw mount !

-Les

[Brett Erskine]

Frank-
To answer your question...Yes AND No. All 35mm lens project a image larger than a 35mm focusing screen (36mm X 24mm) BUT how much bigger is the question. I hear that they are all slightly different. The lens I happen to check was a Canon 50mm F1.8 (or f1.4 I dont remember). That particular lens projected a image that nearly filled the entire GG measuring 2 1/4 inches square. If I had to eye ball it I would say the image was 2-3 times larger than a 35mm focuing screen.

What does it all mean? Well if that image size is aprox right for just about all 35mm lenses then you should be able to shoot without any achromat lens (at least with the DVX100. I havent tested other cameras)

As far as a rod support system - Im with you guys. Most cameras only have a 2 or 3 threads in the front of their built in lens. The first time you bump your adapter hard on something...well I wouldnt want to be you. You likely to watch your adapter and film lens fall to the floor and break - only to find later that thoughs 3 threads that are a perminate part of your video camera are also broken. You may never be able to thread ANYTHING on front of your camera again. No thanks.

Which brings me to my next question. Can I see pictures of your rail system Giroud?

-Brett Erskine

[Bob Hart]

A furthur affirmation of a support system for the mount. Close coupling still imposes a load on front of the camera even if the lens hood mount is used.

There is quite a lot of compliance in the lightweight camera body and it is not good to exercise that too much.

[Giroud Francois]

ok , first pictures.
http://www.giroud.com/miniDV/frame1.jpg
http://www.giroud.com/miniDV/frame2.jpg
http://www.giroud.com/miniDV/frame3.jpg
http://www.giroud.com/miniDV/frame4.jpg
probably a good pass with a black paint spay will help to get a more professional look
not seen on picture is the hires LCD monitor from sony, allowing to make sure that focus is ok. It will be fixed just behind the cam in a way you can tilt it a bit .
All is made from very cheap aluminium profile. You just need to cut and assemble together. The full stuff cost me less than 35$.
tubes are 16mm diameter, but unfortunately i do not respect the standard distance between them (should be 80mm) to be compatible with professional devices. not too bad as i do not plan to mount expensive professional item on it anyway.
the lense as a front thread of 55mm and i found an adapter to 58mm so i can mount my wide angle (canon WD58 or my anamorphic wide lens -century optics)
if i got time, tomorrow i 'll put some shot from the camera.

today i was to a photographer shop to see some lenses.
I compare several 50mm 1:1.4 from minolta, pentax, canon, nikon.
Despite having the same optical specs, all these lenses were really different when comparing the diameter of the lense.
there is at least 5 or 6 mm in difference in diameter between the smallest and the biggest lens.
That means you can get a 50mm 1:1.4 lense that has a rear lens of 30mm of diameter when an other lens can have 36mm of diameter. this makes probably a huge difference regarding hotspot and vignetting.
i am starting a 2nd prototype with oscillating gg.
I think you can easily solve the problem of excentric shaft.
you drill a plate and insert the axis into the hole. you just need few mm to get the roller bearing to plug on it.
then you make your Delrin parts twice as high as the roller bearing. in the first half you will put the axis centered. the second half will be drilled to make a hole to cover the roller bearing.
the trick is to drill that hole slightly out of center. that is easy, probably even more than drilling it centered.
an other way would be to drill the second axis out of center, with as better result that the delrin part turn centered.
all the stuff should not exceed few milimeter high.
i thing the delrin part should have a big diameter so you can outcenter the 2nd axis heavily. the result will be that even a slow rotation will induce a big translation. that requires a bigger glass but should cause less vibration.