Oscillating a one piece fresnel/GG
 

"This may have been mentioned a while back, but by oscillating a focus screen ( like from a 35mm or medium format camera) with a fresnel already "built-in" to the ground glass, you should be able to do away with all the condensor madness. The fresnel lines should be invisible because the screen is moving."

Unfortunately you cant do this without another problem showing up. If you do you'll find out that your hot spot has suddenly reappeared when the fresnel is put into motion.

This happens because the fresnel is focusing light roughly to one point. When you move the fresnel in any way your changing where that point is pointed as it relates to the CCD's. Bigger the motion worse the hot spot effect will be. Now IF you could get it to oscillate in a path that is extremely tight (I mean no more than 1 or 2mm) then it shouldnt cause any problems at all. But having such a small movement means you'll have to move it quite a bit faster in order for the grain of the GG to "disappear". This is exactly what Im currently attempting to do. I'll let you all know if it works.

<<<-- Originally posted by Les Dit : OK, link sent. Let me know what you think! -->>>

hi

can i see the footage as well. also has anything really come of the oscilating GG idea. im planning to shoot with and xl2 and some sort of homemade mini35 device with can ef lenses.


lilbowrabi@hotmail.com

<<<-- Originally posted by Les Dit : OK, link sent. Let me know what you think! -->>>

hi

can i see the footage as well. also has anything really come of the oscilating GG idea. im planning to shoot with and xl2 and some sort of homemade mini35 device with can ef lenses.


lilbowrabi@hotmail.com

Link sent.
-Les

I want to see!

oolsen1@ec.rr.com

Curious...

Why all the talk of oscillating the glass and no ideas of spinning it anymore?

If you step back and think about it, there's a perfectly stable way to rotate ground glass from its edge -- instead of its center -- and thereby maintain the compact size, and relatively low cost of the current adapters. What you need to do is sandwich your ground glass between two ball-bearing rings, with machined teeth at the edge of the GG. Then, mounting a motor externally, rotate the GG from its edge.

I've already worked out light sealing issues in theory but have yet to execute my plans -- just figured it might simplify things for those of you who are finding moving GG necessary (understandable at higher resolutions.)

- jim

That way you will need a really high RPM motor I guess...or a big gear....

for your info it was made on first model of the real miniDV.
They stop because the "vortex effect".
Obviously rotating something has always a common point.
The center moves slowly than the outer edge, even the center point does not move at all. this is the problem.

The key is there is a difference between rotating the GG and oscillating it. With the later, there is no common spot that will have no motion and be visible.
-Les

Good point. Thanks for that. Though this is a problem only if it's assumed that the projection is cast on the glass's center...

I don't understand, Les -- what do you mean?

- jim

Jim, in the design I used, the glass is moving in an 'orbital' motion of about 1.5mm radius only . The middle is moving the same amount as the center. The glass is not spinning, it makes little circles.


<<<-- Originally posted by Jim Lafferty : I don't understand, Les -- what do you mean?

- jim -->>>

Yeah, I get your design -- my question pertains to the above suggested spinning glass as a GG spun from its edge -- if the image is projected off-center, and the glass spun sufficiently fast, what visual anomalies would arise (if any)?

As a related note -- why hasn't anyone taken up the wax process? Are the claims of it showing no grain false, or is the process too costly -- in time, money or energy?

- jim

Oh, OK Jim.
I think the spinning glass can work just fine. The adapter will be a bit bigger than an orbital system, obviously.
I don't see why spinning it from the edges would be of any help. You can't use the center anyway, so there may as well be a tiny axle there to spin it.
-Les

Well, if you spin from the edge, you can use space up to the center, and the rig will likely be a smaller design than one with the motor placed at the center -- especially given that where a center axle rests, you'd have to also place your motor just behind (or further complicate things with belts or gears to move it off-center).

I'm getting somewhat handy at 3dsMax -- when I get the time, I'll put up a model to more directly explain what I mean.

- jim

Jim-
I undestand what your trying to say and IF you put the motor in the middle with a axis right there then yes it could be too large and cause a line of sight problem.

IF you want to rotate the GG from the outside like you mentioned I might recomend the smoother, quieter option of using large ring bearings. If you havent heard of them before image a sealed ball bearing thats as large as say a CD but has a inner hole just a few mm smaller than the outer diameter. In other words the bearing is the size of a CD but only a few mm wide and deep leaving a huge opening in the middle for you to see your image.
By mounting your GG to something like this you dont have to work about it shaking at the edges and ruining focus.

Its definately easier to build than a oscillating GG mechanism BUT your setup will be at least twice as big as it would have been if you had oscillated it. Also there could be a small chance that the "vortex" grain problem will still be there if you rotate it.

Personally I would oscillate it but if you dont have access to precision tools to make a oscillating adapter then the ring bearing is going to be your second best choice.

-Brett Erskine

To Les Dit

I just read about the 4 shaft 12 ball bearing offered kit, with motor,belt, misc parts to make a complete GG orbiter for $350,

Is that offer still there? If it is - could you then please send me some further info to my e-mail??

Thanks

Email sent.
I'm trying to see if at least 4 people need these kits. Then it's a go.
-Les

Thanks Brett -- I'd only rotate the glass anymore if I could do it at a smaller scale than you're speaking of.

Otherwise, I'm editing footage done with my static adapter at the moment and I'm finding the grain all but disappears on an NTSC viewing source, and for web delivery it's gone when the file's compressed to even a 1mb/sec, 360x240 Quicktime file. Since the grain really makes itself evident in the highs, a little Glow filter does a bit to suppress it as well.

The real problem I'm having is the damn dust -- there's four glass elements to keep clean with this thing :(

edit: Just now reading this thread closer from the beginning, and Giroud's stills look fantastic! I'd love to see some footage, though...

- jim

Les
 

Les,

i really need this Kit.

this one works with the JVC HD10U ?

send me the email too

danielmoloko@hotmail

ciao

To Rai Orz

Have you made a working relaylens for the XL-1????

<<<-- Originally posted by Rai Orz : Justin, in principle yes......Arround the 35mm solutions, i think this products are possible:

Prism-Set, suitably for the backside for UP-Side-Down correction

Relay-Lens-Set for XL1 or other

The products are here on my table, but yet i dont know details about prices or delivery. -->>>

<<<---Have you made a working relaylens for the XL-1????--->>>


Yes

Would you share how you made it???

Perhaps you could reply on the Canon XL-1 Relaylens for use with the 35mm adaptors thread (so this thread isn't messed up):

http://www.dvinfo.net/conf/showthread.php?s=&threadid=23377&perpage=15&pagenumber=7

Thanks!

I am interested in Les' Kit too
 

Hi Les,



Just want to let you know let you know I am interested in your kit too.
I also would be interested in getting an email from you as I have a couple of questions, including about the possibility to adapt your kit for medium format GG (see Brett's posts), as I am using a DVX100 and would be glad to get rid of one lens and get some extra contrast and brightness at the same time.


Thanks in advance for your reply.

Best Regards,


Emmanuel

Les,

Could you send me some information as well? My email, if you can, is admin at weet.us

Email sent.
-Les

Me too!

jamey at sunrushmusic.com

I'd be interested as well Les.

jon1million at sympatico.ca

Thanks!

Hi Les

How is the osc. device coming along - any news?

OK. I'm a complete newbie to this whole 35mm adapter concept.
I have been doing my best to read through all these threads (there's a LOT of material to sift through!) but I may have missed a few posts (in fact I'm sure of it).

Firstly, I've gotta say this is really a fantastic project! Congrats and kudos to everyone working on these.

I'm bitten by this 35mm bug, and had a few ideas I was considering for my own project and was curious if anyone has had success or failure with any of this....

1) What about a small speaker connected to a tone generator for an oscillator? Would that be too weak? Maybe it depends on the mass of the GG material.

2) Would a "frosted" bit of transparency (overhead projector "film") on a slide frame be a sufficiant focal plane, or is genuine ground glass the preferred medium?

3) I've seen broken camera bodies of all makes on ebay in the $10 range. Could the front plate from these be used for a lens mount?

I have several Minolta lenses which are now mostly unused since I went digital. Would be great to put them to use on my GL2. :)

Thanks.

thank you agus
 

Hi welcome aboard I feel guilty not offering advice at what won't work. I think after building everyone of the devices. the second augus 35 in the americas. this needs to be built in a optical tube
there is no way to get pvc , plastic project boxes , or even lens tubes to the tolerences we need . I am proud of my agus35 and bring it out @ every party. I think the focal length of
50mm camera lens to ground glass is about 1 1/4 inch thorlabs sells a stackable tube 1 1/2 that will fit a50mm 1500 grit ground glass that cost $14 a50mm plcx behind this and you have your static adapter. the cool part is these parts are the base for a ocillating adapter I am building . the empty lenses tube model was good but the tubes could not handle the weight of the camera lens and get a precise focus with the ground glass .
I t came apart and died a glorious death in times square. you can all wait untill my parts come in and I will tell you how all this works.

Hi Anders and others,

I am busy adding some CNC to my milling machine, so I haven't got to the next stage of improving my oscillating GG mechanism yet.
I do think there are enough people to go ahead with a limited production run of these, for $400 each. I will prepare a simple web page for easy information gathering for those who want one.

Again, if you are interested and want to see the high definition video clip of my prototype in action on a rack focus, send me an email an I'll send you a link. I have to do this with email because last time hundreds of people downloaded the 22 meg clip and used up my bandwidth!
Thanks
-Les

Just curious, for those of you who have built versions of these before what is the focal length of a 35mm lens in, say, inches or mm? Does it change dependent upon the manufacturer?

focal length
 

I think the distance is 1 1/4--- 1 3/4 for slr lenses. If you build the system in this tube you could adjust it to any slr lens thread retaning ring to focal point add ground glass and plcx and you have a static adapter .http://www.thorlabs.com/ProductDetail.cfm?DID=6&ObjectGroup_ID=213&Product_ID=1481

ocillating adapter
 

this is the link to a cage similar to the one I plan on using for the oscillating adapter . It will fit precisely on the tube system the other end will also have more of the tube system then to a c-mount then lens. from one end of this tube to the lens .the tolerences will be perfect. the failure of my filter ring system
was the tolerences . this has to be perfect.


http://www.thorlabs.com/ProductDetail.cfm?DID=6&ObjectGroup_ID=183&Product_ID=474

Re: ocillating adapter
 

Yes, the tolerances are the critical part of this design. The alignment of the bearings and the shafts is the hard part.
The one I make has to be good enough for my JVC HD camera, which shoots 1280 x 720 video. Not much room for error!
-Les


<<<-- Originally posted by Richard Mellor : this is the link to a cage similar to the one I plan on using for the oscillating adapter . It will fit precisely on the tube system the other end will also have more of the tube system then to a c-mount then lens. from one end of this tube to the lens .the tolerences will be perfect. the failure of my filter ring system
was the tolerences . this has to be perfect.


http://www.thorlabs.com/ProductDetail.cfm?DID=6&ObjectGroup_ID=183&Product_ID=474 -->>>

static adapter
 

hi everyone this is a still from a clip made with a filter tube version .the plcx is about 3mm away from the ground glass could not get sharp focus . this was made with 1500 grit ground glass
and 60mm fl 50mm plcx the camera is a one chipper. the tube system should correct the focal distance to the ground glass and allow the plcx to fit directly on the ground glass.


great bokeh



http://www.dvinfo.net/media/mellor/PDVD_540.BMP

That looks pretty good to me. Is that from a static or oscillating glass? And is this the 1500 grit disk from Thorlab? I'm going to opt for their lens tubes as well . I just hope the threads actually fit a 50mm ring.

Jon

This thread is not for static adapters.

While stills may be fun to look at, the only real test is moving footage with out of focus objects and a slow pan, full resolution at a minimum of 5 megabits/sec compressed data rate. That's where almost all of the adapters show the undesirable 'fixed pattern grain' that makes it unacceptable for work other than some kind of artsy fartsy dream sequence.
-Les

ocillating adapter
 

les I am building a ocillating adapter all of the static parts will be used in the final design this will be the design. camera lens c-mount tube , cage system back to tube . this is what a cage system looks like. the tolerences on this are .000005.
lens tube (2)$56 cage rod (4) $24 cage plates $60 .
$140 total. the focal plane on this system would be perfect .
We would all be able to build this together . with part numbers
and test results .you could start with a static adapter and add on as
designs become perfected


http://www.thorlabs.com/NewGroupPage...ctGroup_ID=180



http://www.thorlabs.com/ProductDetai...roduct_ID=1480


http://www.thorlabs.com/NewGroupPage...ctGroup_ID=180

Richard,
Thor labs has some nice stuff! I have some of their mirror mounts for a laser project I was building.
So the missing part is the part that causes the motion of the GG.
Whatcha gunna use for that? That is the hardest part, in my experience. The eccentric.

I'm glad someone else is trying this, I will be fun to compare notes!

-Les