great work dogus. your design looks great.

could you tell me the diameter of your eccentric shaft .

the outer diameter is 10mm and inner is 5 mm..which makes a 2.5 mm diamterer of motion...
( the measurments of the mill on dodo35-4.jpg picture)

so it looks like the inner diameter of the ball bearing is 10mm . what would the outtside of the ball bearing be .

the diameters are inner outer

big bearing ... 10 19
small bearing .. 5 16

Jim, Richard, Dogus, Les, Brett, etc., etc... i've been off the thread for a bit but you all have great new ideas and links to quality parts guys that i couldn't find previously. i'm very impressed. a couple of questions...

Dogus, what type of motor are you using in your schematics, looks like a low voltage Radio Shack type motor(?)

Jim, as far as parts, i'm looking at 52mm fittings, it would only seem right that the 2" lens tubes from Thorlabs you showed probably would work on 52, but it might be you are using 49mm type of housings for the inside(?)

Richard, also thanks for your great efforts also and your recco's and links to boot. i'm having some trouble visually seeing how the "oscilating glass" works, but i'm VERY interested in seeing if i can improve sturdyness and quality even more. would it be possible if you could give me another example that might help me understand more.

Les, i've had some success with the lens adapters i've made so far, i am also interested in the quality you've achieved so far, could you send me a link to your video tests so far??? please send to dinor@hotmail.com

tkx all...

Dino, link emailed. Send me your comments.

Dogus: I can't wait to see your sample video too, gook luck with your project! Please keep the video high quality as far as compression, if and when you post. Stills of the video are useless to see whats going on, as you know.
-Les

I spent some time with this. And I think this is going to work perfectly. great job

Dino,

I'm unsure about the fittings of the parts. I've gone ahead and ordered the coupling because my best guess is that:

Given that the tubing is 2", with an interior diameter of 50.08mm, threaded on the inside, I will at the very least need an externally threaded coupler to attach the tubing to a filter or step-down ring. That said, 49mm is the closest from among the choices of standardized camera parts to 50mm. So, it's my best guess that this setup should work. Consequently, I'd also bet that 52mm parts will be too big -- nevermind the fact that the tubing is threaded on the interior side.

My parts have already shipped, and are due to arrive on Tuesday -- I'll let all here know right away as to my success or incorrect guesses :D

- jim

c-mount
 

I found a c- mount adapter for the 1 inch tube but don't know about the 2 inch tube yet.

http://www.thorlabs.com/ProductDetai...roduct_ID=1454

Medium format adapter
 

Dino great geat work! We're on the same page - design and medium format wise. I've been pulling my hair out trying to find offset shafts like yours. You said you had them custom milled. If possible, could you quote me a price to have four more made and sent to me? Drop me a email and I'll send you my phone number.
(berskine@mail.com)

Also I noticed you were using a Beatie screen w/ grid markings. I take it that they have no effect on the image once the GG is in motion. The second issue that is surprising to me is your using a focusing screen with the fresnel and GG as one piece. I tried this and encounted a problem and wondered if you have yet to test it and if so how you got over the following issue:

As we all know fresnels exist on one side of focusing screens because it helps reduce the issue of having a hot spot in the middle. It does this by bending/colminating the light to a point - the point where your eye, or in this case CCD is located. Sounds good but put that same focusing screen in a oscillating motion and you move more than the GG. You move the fresnel around right there with it. This causes a problem because that point the fresnel is focusing the light is shifing all over the place - moving to and away from its intended target (the CCD sensor) because the focusing screen and CCD are moving independant of each other. The effect is you begin to see the problem of light fall off show up again. If you turn it very slowly you will see one edge of the frame bright and clear while the other side the light is falling off. Now put it in fast motion and it appears as if only the center of the frame is bright. I hope that makes sense.

So Dino did you see this effect too? If so what are you doing to get around it? Personally I'm fixing the problem by making the GG and the fresnel seperate pieces so that the fresnel is static and always in line with the CCD while only the GG moves. Then I took the idea one step further. I knew that frenels dont produce images that are as optically clear as a traditional lens so I plan on replacing it with one or possibly two field lenses (PCX).

Thats where Im at right now. I'm working with a camera optical engineer to help me find the proper field lens(es) to take over the job of the fresnel lens to produce the ultimate in picture quality.

P.S. Let me know if your interested in a source for custom calibrated medium format screens without gride lines.

dear Bret..correct me if im wrong but the "beatie screen w/ grids..custom mills etc.".. you were refering to me? (dogus not dino?)

bret i would be happy to send you prices and the mills..please drop me a mail at dosealas at tumgorsel dot com.. the beatie screen with grids of course has effect on the final result...i used that screen for testing purposes only..as i found there is a great difference in image quality between the medium and high format..i have made a great research on fresnel lenses..and i have come to this conclusion...when light hits the gg the image is diffused to every direction..light passes through the slr lens and on to the gg...the light enterinng the slr lens comes from all directions also but the light amount that passes paralel to the lens is much more than light rays that go through the lens non-paralel..since thouse non-paralel rays hit the inside on the slr more and dont find their way out..this results as the image being brighter in the middle and dark on the outside .. the fresnel lens has the property of changing the direction of light rays (paralel and non-paralel) to the paralel path...so theoreticaly there should not be any heterogenese light..but this is theoretical and has not been tested yet.. i hope to be testing in this week..(i have final exams in a few weeks and i dont know if i will find the time)..but i have tested on other gg's for i am ready for such a fault in the fresnel lenses..but i must admit the fresnel gg has very low light loss..which is really amazing when compared to ordinary gg..in my experience plastic and glass too differ..the few plastics i have tested all had very low light transmition compared with glass..and even 4mm glass compared to 1.5 mm glass gives a great difference in f-stop values..i think if the beaties screens give results as you mentioned...the step i will take to get over this issue will be your way.

bret what was the gg with fresnel you used?yes i am still studing on this project and i would love to read more about the custom calibrated medium formats.

les can you also send me a link of your work and images..

dino i have not considered any kind of motor yet..i want to first assemble the parts and then see how much power is needed..i have talked with a remote control helicopter freek who makes his own helicopters..we have gone together through the subject and we have left enough space covering a wide range of motors in the design..

Dogus-
Yeah sorry I was thinking Dogus and typed Dino. As far as the issue with the fresnel lens. Its pretty easy to see the problem. Simply hold the screen in front of the lens your planing on using and move it around a few mm by hand. You'll see it.

The calibrated focusing screens I was talking about are the Maxwell screens. They come in all sizes and focal lengths. The fresnel is made up of tighter/sharper groves then even the Beatie screen. They are reguarded by many medium format photographers as the best out there yet many dont know about them because I believe you can only get them thru Maxwell Precision Optics. Keep in mind though that these are one piece fresnel/gg screens so unless you find some way to get over the issue above they will be useless. However they will work great for the people designing static mini35 adapters.

Anyways the email is on the way.

eccentric shaft
 

hi Dogus do you think your machinist. could make a smaller version of the eccentric shaft . 5mm or 6mm ?

yes i suppose he can make them aswell as long as you send a detailed plan of the mills you want..

eccentric shaft with parts list
 

thank you dogus. the plan is to use this parts list

1http://www.thorlabs.com/ProductDetai...oduct_ID=11138

2http://www.vxb.com/miva/merchant.mv?...egory_Code=6mm

3 this will be a link to a 6mm eccentric shaft

4http://www.thorlabs.com/ProductDetai...roduct_ID=1018

5 http://www.thorlabs.com/ProductDetai...oduct_ID=36109

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

the basic plan is 3 cage plates drilled out to fit 10mm od ball bearings. fit bearings in 2 cage plates . (4) 6mm eccentric shafts fitted in the two cage plates. about a 2" by 2" plate with lens holder nested in the middle of the plate; fitted on6mm holes in plate

third cage plate with 1 inch tube ajusted focal length . next c-mount to slr lens

i think i put it in wrong words..i ment cad plan..this is an example of my old design...

http://www.tumgorsel.com/dosealas/dodo35/cadfile.jpg

i can get you custom made mills if u send a plan like this:)

by the way i received my plates.!!!

http://www.tumgorsel.com/dosealas/dodo35/cutplates.jpg

Dogus-
Did you have all thoughs parts professionally custom made? What was the total cost?

Alright...

Got my Thorlabs parts today. They are VERY LIGHT :O

Oddly, the externally threaded coupler -- listed as an accessory to the 2" tubing -- doesn't fit the 2" tubing. I'm frankly baffled as to why this is, or how you'd use the thing at all -- the threading is the exact diameter of the 2" tubing, not smaller, so you can't insert it into the tube :(

The "adjustable focus" piece isn't as elegant as I would have liked, but it will work -- I figured the adjustments would be made just as you make focal adjustments on a lens, by rotating an implement, it would advance or recede. Instead, it's just a threaded tube that you screw in or out of the 2" tubing, that has a locking ring. Not elegant, but hey, it works.

Otherwise -- 49mm UV glass ought to fit perfectly inside the tubing (haven't had time to test this yet), though any 49mm stepdown will not work with the 2" tubing -- I'm hoping a 58mm-52mm stepdown will work properly with the Century Optics achromat, but will not have the time to test this hope out for another couple of days.

Blah -- typing this quickly before leaving for a relative's b-day bash -- sorry for the typos and other grammatical weirdnesses :D

- jim

yes brett..all except the c-mount for the pentax slr lens..strangley when i made my first design.the parts had a thickness of 4 and 3 mm's..it cost me around 90 dollars...i paid that amount..and then we found faults and bad engineering in the design (too heavy)...so i took it from the beginning used 1mm thickness and strangly it cost 40 dollars..i dont know why there was such a price change...if it would have been the 40 dollar first and then the 90 i would have asked:)...they are cut on a laser metal cutter..they are really heavy industrial machines ( i heard the purchase price for such a machine was around 1 million $ ??? ) , but my designer had worked with the place before so i could get this stuff done in such a short time...i live in izmir,Turkey.. and i heard there was about a dozen of these machines in my city..i bet there should be more in cities in europe..if anybody gets the chance..could they inform me on the costs for such parts (as can be seen here " http://www.tumgorsel.com/dosealas/dodo35/cutplates.jpg " )

i have done a test setup with the parts..the laser cutter is so presise that the bearing need to be hammered on the plates to get them in (thats what the guy operating the lasercutter told me to do) you cant get them in bare hand..i am happy with them..tommorrow we will weld a few parts..through some paint on..i have a few parts still missing so i think the final product (without the motor ) will be running (by hand that is..or using as stable gg ) in 2-3 days..

Dogus-
Izmir, Turkey huh. Some great sites out there. I was out there earlier this year shooting Ephesus and went on to Istanbul and Antalya. One of my favorite shoots was some aerials in Capadocia. Heres the footage>
http://www.cinematographerreels.com/gorematurkeymov.htm
Anyways Im very impressed with your setup. Let me know if I can help you in any way. What brand film lens are you planning on using? What format size (645?) Since we are both doing medium format adapters lets exchange info to make this work. Do me a favor and measure your flange focal length and the distance between the CCD plane and the GG. I'll run it by the optical engineer and see if I can get you the specs from the proper plano convex field lens(es).

I received my GG from Satin Snow Glass the other day. I must say that its extremely fine grained - finer than anything that I was able to do by hand. The only thing I can say against it is they are made of glass instead of plastic which means they are heavier. This might cause a excessive amount of vibrations when put in motion.

yes i had seen your footage before..real nice pal!!..

i am using a pentax 1.1.2 lense..actually its a 35mm stand format lense..i got it for around 100$..this project has flew higher than the budget i targeted along time now!:) ..but changing the lense is so simple as i have designed it so it is open for later modification.you can see in the cad drawings..i have a sony trv-940 and the damn thing can focus to a subject nearly touching the camera ..but it does make lighting issues since the object is blocking the light, so i used a transparent object..and calculated that the camera and the gg have about 1-2 cm distance..it can focus easiliy..but the closer it is the biðgger the image will be without the using of macro lenses...but i cant answer your question in terms of distance between ccd and gg..dont know how to? the distance between the lens and gg have a measure between 4-5 cm ..i have desiged the system with a distance of 4.5 cm i will pull an infinite focus and than adjust it aquaretly..the gg can move 5mm nearer or closer to the lense by screws which will be tighting the bearings..

brett i think glass will pay off because plastic has to be really high quality to satify the quality glass gives..


i am also interested in the snow glass..can you send a few images of it with an image projected...

oops..about the message i sent before..the price was for the metal parts only..the mills cost about 30 dollars each..i paid 4-5 dollars to get the srounding metal plates rounded..and another 15 dollars for the custom 37mm screw for the trv..

I was looking at your design and Im alittle curious what your planning to do for a few things:

1)How do you plan on fixing the bearings to their coresponding plates? You mentioned that its a tight fit right now but from your diagrams it looks like frictions the only thing holding them in place. Are you going to spot weld the bearings to the plate or use some other hardware to tighten them to each other? The reason why I ask is because it seems like vibration could eventually make the bearings pop out of their plates they way it appears in your diagram.

2)How are you mounting the GG plate to the oscillating shaft and then securing it?

Personally I came over these two issues by using a oscillating shaft that was threaded. This way I can use lock washers and small bolts to tighten down on the bearings from both sides and keep everything in place and solid. It also keep the shaft from spinning inside the bearing.

brett : regarding the shaft you are looking for, how long does it need to be . and what would the diameter be

brett..

1- my designer told me that the bearing had to be hammered in position..he mentioned welding the bearing would damage them..but he also added that spot welding might work..i think i will have to ask a few people...i let you know when i find out..

2- yep i have the same thing in mind.. my new mills will be ready tommorrow..except for the place where the rubber bands will be..i will put up a picture..

and brett about the snow screen..i sent an email but it returned as no such mail..can u give me a contact..

Richard-
I have some extremely tiny bearings that I bought so that tolerances would be real tight but if you have a great source for offset shafts I'd be willing to find new bearings to match whatever you can offer. If you got something by all means send me the info. Thanks.

Dogus-
Here you go: BErskine@mail.com
The mail box is getting pretty full again so let me know if your going to send a larger file.

oops:) brett i ment i mailed to the satin snow people and i recevied no answer..who did u mail...

sorry about the confusement pal:)

I called. Heres their site:
http://www.satinsnowglass.com/index.html

Thorlabs parts
 

Hi Jim
I was wondering if you were able to do any more tests with your new Thorlab parts. Particularly the issue of what stepdown ring fits the threads.

Did you or Richard also order some of their 1500 grit ground glass? I'm likely placing my order next week and was wondering if the glass would be worth adding to it. The finest AO I've been able to find here is 1000 so I'm assuming that the 1500 would be even better.

Thanks for sharing

Jon

P.S. Congrats Dogus, your setup looks great!

The stepdown is 52mm from whatever your original lens is. For my GL-1 it's 58-52mm.

The glass for inside -- if you want to use something cheap -- should be 49mm UV filters. You have to keep the ring on and it fits fine -- with the glass alone it's a bit small, but anything larger probably won't fit.

- jim

Multi Format DOF Comparison
 

Thought you guys might like this multi format DOF comparison.

To give you a true sense of what each format will give you in terms of DOF I've kept the FOV the same and the distance between the camera and actor the same - thus different focal lengths between formats. I also used real world lenses commonly available for each format which explains the different minimum f/stops used. For the following comparison an actor is placed 10 ft from the cameras postion. The camera is never moved nor is the FOV changed. I choose a common composition - in this case a medium/CU shot (mid chest to top of head) of the actor. Here are the focal lengths and DOF of available lens in each format:

Medium Format (645) - 200mm(FL)/f2.8 = 2.07inches(DOF)
35mm (Still Camera) - 135mm(FL)/f2.0 = 1.92inches(DOF)
35mm (Motion Cam) - 85mm(FL)/f1.3 = 3.62inches(DOF)
16mm (Super 16) - 50mm(FL)/f1.3 = 6.31inches(DOF)
2/3" (CCD Video Cam) - 35mm(FL)/f2.0 = 2ft, 2inches(DOF)
1/3" (CCD Video Cam) - 18mm(FL)/f1.7 = 3ft, 4inches(DOF)

Again the reason why their are different FL for each format is because they all give the same FOV from the same subject distance so in other words they are the same equivalent lens for its format.

Medium format image size/gg is 2.7X larger than 35mm (Still)

Brett:

Just want to clarify something--your 35mm and 16mm numbers seems to be off, but that's probably something to do with the different formats available within those gauges. Were you using a calculator based on field of view? If so, this is a horizontal measurement, but the vertical height of the frame is more relevant when considering a shot of an person (i.e. mid chest to top of head). As an example, standard 16mm and Super 16mm frames have the same height, but the Super 16 has a greater horizontal field of view.

Nominally, the difference between 35mm and 16mm should be a factor of .5x.

Yeah thats exactly right. I was basing my FOV on a 35mm 1:66 frame since it was the closest to all the other formats. I knew that everyone has their preferance between full screen, 16X9, 1.85 and 2.39 so I decided to try and keep the horizontal FOV the constant in each example but you right the important thing here is the vertical FOV because we are talking about shooting actors. If however you keep everything pretty much a 1:66 ratio for each format then these numbers should give you a pretty good idea of the DOF for each. If you would like to post the exact numbers by all means please do.

Satin Snow(TM) Ground Glass
 

Good morning everybody.

I am the owner and producer of Satin Snow(TM) Ground Glass.

If you would like to contact me, our email address is:
gglass@satinsnowglass.com

I have received a few emails about these types of projects and currently would like to find out, which sized ground glass screens would work best for the applications you folks are using them for, I have been told that 55mm and 52mm are two of the sizes that are being used.

Would you require these in regular screw in filter rings, such as used with 35mm cameras?

Anyway, if you would like, I will try and see what I can put together that may be of assistance to the types of projects you are doing, currently our main focus has been Large Format Film Cameras, but have sold a few screens for use in the DV industry and I am sure I can come up with a solution for those of you that are interested.

Thanks again.

Dave Parker
Ground Glass Specialties
Satin Snow(TM) Ground Glass
www.satinsnowglass.com

David.

There is another method which uses a spinning groundglass to furthur enhance apparent resolution by moving the "grain" of the groundglass through the image faster than the camcorder can resolve it, virtually eliminating it. However, a coarser texture to the groundglass will still affect resolution.

Awhile back, I bought in raw cut optical disks from Ohara in Japan. These were supplied as a special order of 10 with a 15mm diameter center hole and outer diameter of 120mm, a whisker over 5 inches which replicates the dimensions of a plastic compact disk. The thickness was 1.3mm and dressed down to about 0.9mm before the cut marks polished out. The concentricity is an issue for balance but a groundglass texture of uniform quality across the glass means the rpm can be kept down to 1500 or thereabouts which limits vibration.

If you can replicate the compact disk profile with your product at an affordable price, there may be a few making AGUS35s (nicknamed spinners) who might be interested. AO5 dressed spinning groundglass seems to yield about 600 TV lines of resolution at best. Finer than AO5 makes the groundglass too transparent. Thanks for the interest in visiting.

There are some on-site images you can find here at
www.dvinfo.net/media/hart and www.dvinfo.net/media/mellor There may be others here but I don't know of them.

hi : welcome a board david. after trying many types of ground glass the best so far is the optmo sigma 1500 it is 50mm and will fit perfectly in a static tube system . this is the one to beat .
it,.s price is $24 the $ 14 thorlabs is on order and will let you know how that looks maybe your technolgy can better these options. for static devices . but I just got a chance to test out the device that we all hope to equal .the $26,000 ps teknik hd pro model and saw first hand the quality of the ground glass in the $26,000device.
and the optmosigma equaled it .as a matter of fact I think they use a lower grit size than the 1500. for a brighter image
it was amazing the amount of grain that you could see when you powered down the motor . the ocillating disk was about 55mm . I think with future devices the biggest concern is precision of the focal plane. the camera rental place told me that the first generation of the ps tecknik with spinning glass
had a lot of complaints .1 was the vortex of hell. this is caused
by the image not spinning at the same rate the outside of a disc will spin much slower than the inside this was corrected with the $26,000 ocillating adapter . motor vibration was the 2nd complaint . brushless motor and precison parts, and we can make this. maybe there is away to make a piece of glass so good we will not need to ocillate it. that would be a dream

maybe there is away to make a piece of glass so good we will not need to ocillate it. that would be a dream

That's the idea behind the microwax design -- my shipment of wax is pending, but it seems to me to be the only realistic setup that promises a grainless static adapter.

For someone like myself, moving parts, a motor and power supply (not to mention a larger profile) make an oscillating adapter out of the question. For these reasons, if microwax doesn't work, I'll just abide the grain.

- jim

I've just spent the last hour reading this thread.

It's fascinating.

I'm sure you know that this business of a video camera looking at an image formed on a ground glass has been around for years in the form of video-assist cameras taking a peek at the ground glass in a film camera. (In fact, by some very weird coincidence I posted in this very forum yesterday about how clients often mistook the resulting image on the playback monitor as being a telecine of the film rushes!)

Here's an off the wall idea. Suppose you keep the gg stationary, take the lens off, and record an image of the gg illuminated from a light source in front of the camera assembly. You then subtract this image fom the image you get when you have the lens on and focussed on a target. You would have to ensure that the gg stayed absolutely in position.

Also, you might find it interesting to check out the Spintec Lightweight Rain Deflector

Good luck!

I have found a self adhesive sheet of frosted material from AVERY the same people that make the labels. Probably any sign shop have some scraps. Worth to have a look.

The problem with such materials Valerie is that they have a thickness. Once the light hits one side it will form a sharp image, but will continue to diffuse as it travels through, and become slightly blurred by the time it is viewed from the other side.

A ground glass has a diffusing surface on only side and avoids this.

I personally don't understand how a hot spot is avoided - hotspots are a real bugbear when rear projecting film onto a traditional cinema screen.