Oh no of course not. The GG will be a separate product available to buy for people who cannot afford the complete adapter. There are hundreds, maybe thousands of people out there who have DIY adapters but dont have the perfect GG or who need a replacement GG. Our aim is to cater for people of all budgets and requirements. If someone has an adapter, the last thing that they want to do is shell out lots more money for another one, instead they can just upgrade and buy the GG.

The whole concept of the 35mm camcorder DOF adapter market is to cater for the film industry where big budgets or large sums of money for equipment are not available therefore we aim to cater for everyones needs.

I hope this answers your question.

Well if the grain is ok without moving the gg, why would anyone bother moving it, and introduce the bulk and noise of a spinner for no reason? Making a big gg for a spinner strikes me as a lot of wasted effort if you don't need to spin it, that's all I'm saying.

I didnt say it had to move.

The rotating option is purely only for the adapter, we are not saying that it has to be spun, all we are providing is a GG of a particular diameter designed to fit a rotating adapter to save the cost of having to buy a static adapter. As a rotating GG is generally attached from one side we have developed a seal to ensure that no glass separation occurs to extend the life of the GG.

The GG has a different seal in our static adapter and is of a different diameter so the GG cannot be used in a rotating system.

To simplify your question we will provide 2 GG products.

- One for a static system

- One to fit an existing rotating adapter (GG does not need rotating)

Our website is near completion so sample footage and stills will be available www.digi35.co.uk shortly

For the uninitiated amongst us, what is gg ,some kind of lenes filter or fitting?

It is the focusing screen onto which the image is projected from a 35mm SLR lens. The camcorder records this image. The main concern is visible grain in the material.

Tony, if you plan to create rotating gg option, then 90mm diameter would be a perfect choice. it can be mounted to a cd player motor or a pc motor and have the perfect amount of area left for a 36mm by 25mm frame. that way, your not wasting space by making a much larger cd sized disk.

the only reason people used cd-r sized gg was because thats what was avaible. it in no way needs to be that big. take the Sg35 for instance.

Due to the middle and outer seals we would have to extend the diameter slightly to ensure that a 36 x 24 screen can be captured as the seals are quite wide due to the ultra, ultra thin glass.

Tony.

Just a thought. If people are going to use the GGs dynamically in a spinner design, you might need to consider matching pairs of your glass layers. Maybe your lasercutting process is good enough to get the precision where this is not needed.

I found with what I called composite wax disks, that it was very hard to get a good balance and that I needed to spin pairs "dry" on a hub and motor to match them first beforehand and even then there was no guarantee.

There is also a tendency, however slight for each disk to slip offset relative to the other. Just a fraction of a mm was enough. Bot would still go on the hub no problem.

The wax composite disks were quieter than a single glass disk. I think they would have greater resistance to breakage in the way a laminated car windscreen does.

I gave up on wax disks because arriving at a solution was beyond my technical precision skills.

To ensure accuracy, two sheets of glass are sandwiched together and one pass is made to cut the glass therefore the glass underneath is near perfect to the top piece. O-rings are added to the seal to ensure no movement or separation occurs. The composition of our GG does not consist of any form of wax.

All the GG that we will supply is for a static solution, not rotation is needed. We are only providing a rotating GG to fit rotating adapters as our standard GG for the DiGi35 adapter is of a different size. This is to be a solution for people who already have an adapter but dont want to shell out money for another.

Tony,
How 'grainless' is the GG? Are you able to stop down the SLR lens without grain? Also, how about its diffussion level? This directly relates to the bokeh produced. Only reason I ask is since most grainless static solutions do not produce a very nice bokeh (wax seems to be the exception).

Hi Wayne,

Im going to email you a still that we made using a piece of GG that we made half coated to compare the difference.

Wayne - Sent.

Tony,

OK, i got the email and attached image. I must say im not sure what messege your attempting to get aross with this image, but I must say im a little confused. I feel it fair to post your email here along with the image you sent me, as it sounds a little fishy and think people here should make their own minds up.

I wont say more since you maybe genuine, and I dont want to be unfair if you are, but that image is obviously half guassian blurred in post.

At the time we did not have the correct equipment to carry out tests so we used a half coated GG for comparision. Complete footage and stills will be available in approx 2 weeks.

I see what you mean. I didnt take the image, it was my partner. I was emailed it. I must say that the actual image itself gives it away as where we live there is no house like that. It does look a little to perfect. My actual view would be that the right side would be out of focus is this correct?.

As I said previously I am no expert in cameras etc but I think I have some logic. I have a half coated piece of GG that I can send you if you like, the diameter is 94mm, is this OK.

I also just lined up the line between the two halves and it is too straight. The hlaf coated GG I have is nowhere near a straight as the pic.

This is why I want to have tester do the tests for me to ensure fair images are taken.

I SHALL NOW GO OFF AND HAVE WORDS WITH A CERTAIN SOMEONE NOW!

By doing this can put a reputation down the toilet before it has even started, so all I can do is apologise. 10 GG samples will be sent out shortly so everyone can decide then.

Tony,

So what exactly is the deal with that image you sent me?

I cant say yet, I have just left a voicemail for him to call me back, should call back within the hour. Again all I can do is apoligise if this is the case. I dont know what to look for in these tests until they are pointed out to me, Im still learning. My main part in the project is to design the adapter and seals to enclose the GG and lenses. I have as much experience in this field as a virgin does in the Karma Sutra which isnt much.

As you are local can you email me an address to send a GG sample.

Tony.

Some alternative relay devices can now just come up to 850 TV lines of horizontal resolution off a groundglass image about 30mm wide. That's the benchmark your groundglass must be able to achieve before the marketplace will come hammering at your door.

But if you do develop the genuine article with good bokeh ( quality of soft areas of image ) and the hotspot problem solved, then hammering at your door by customers may reach the desperate intensity of that of the ancient throng at the apothecary seeking the cure for the plague.

As for the .jpg image, if the "clear" area is supposed to be the groundglassed area, it demonstrates a basic misconception of just what these adaptors do. They do not clarify the image but degrade or soften it slightly.

The direct-to-camera portion of the image should be clear, the groundglass portion should be softer. The softer area of your image as posted would suggest a performance inferior to the projects already completed.

There is also no evidence of the differential focus (my words probably not correct here) in the "softer" area of the image, which is the purpose for which these adaptors are made.

That nice sharp edge down the division of the image between soft and sharp can be accepted if the .jpg is a composite or stitch of two separate images representative of the two sections of panel. If this is so, it would have been better to title it as such.

I have published test pattern frame grabs in such a manner.

I think to be credible, you may have to do the hard yards, build this glass into an adaptor yourselves, create the images in realworld conditions and publish the results in a transparent and verifiable manner.

There is a goodwill ethos by and large in this community of tinkerers and engineers in that a sort of open-source process of information sharing goes on.

Tony, for having alot of logic, couldnt you obviously see yourself the image was just a photoshop picture with the guassian blur as Wayne stated. It doesnt take an optical expert to find a fake photo.



here i made a quick groundglass test...
it shows one side coated while one side is not:

http://i11.photobucket.com/albums/a1...ctuureblur.jpg

see how easy that was, it took me a minute to find a picture, and do the blur. who would beleive this was shot of some sort of gg?

Lets not flame Tony, as this could have been a misunderstanding. I live an hour away from him and he says he is sending me a sample of this GG. If it arrives, I will test and confirm his credibility...

I think we have to give Tony the benfit of the doubt here. I've shot with the P+S and the mini 35 and had a quick look at Waynes adapter at it's early stages 6 months ago. I also am going to get a sample of the glass so hope I can shed some light onto this. I'm keeping my fingers crossed it's the real deal.

If I wanted to deceive people I would make sure that I did it properly. That is why I have insisted that people test the GG to ensure a fair test and see for themselves.

May I thank everyone for their help, input and interest.

Tony I hope you don't think I was implying you were trying to deceive anyone. I was trying to say people should stop getting on your case here and let your product do the talking when it's been tested. I'm right behind you buddy. You could potentially blow this 35mm adaptor thing wide apart. Good luck man and I'll email you later about the size of glass.

A fair call Stephen.

I have been looking for a holygrail which resolves like a wax GG without the problems. It costs me $AU50 to land a raw glass disk here in Australia and then I have to do the figuring and polishing, then the one surface of five micron finish.

The whole thing comes to about 15 - 20 hours assuming things go right and don't have to be repeated. Factor in the value of the hours and dressing/polishing materials and somebody else's work starts to become attractive especially if it is of superior performance.

Keep up the good work Tony. R and D is not an easy business.

Hi Tony,

Can your relative glass factory cut out a 90mm diameter glass (3 or 4mm thick) with a center hole same size as a CDR and the glass then coated with your special wax? if can, I would like to order a couple of waxed GG and couple of unwaxed GG. I currently have a DIY mini35 using ground glass which I would like to replace. I don't mind buying some from you if you can do for me in the next couple of week.

Kind regards,

Alex

Email me at ccm@brunet.bn

Thank you for your support Stephen and Bob.

That is exactly what I want to do - let the product do the talking. Hopefully it will say what I hope.

Alex - With regards to your glass the diameter and thickness is fine. You have a choice out of several materials:

- BK7
- Sapphire
- Fused Silica
- Fused Quartz

The first 2 choices are the best for us but the glass is only as good as the spec. Wrong thickness, material, coating = Bad GG.

Email me the exact measurements, material and quantity then I can get a price for you.

NOTE FOR ALL GG REQUESTS:

For all of those who have emailed requesting a GG sample will have to wait until the GG goes into commercial production. Only 10 samples are being sent out for testing. All DiGi35 products both Adapter and GG should be ready for order September 2006 time.

Before that, footage and stills from testers and myself will be available for viewing at digi35.co.uk shortly. A brochure will also be available via post or email which will include product images including accessories, final pricing and other relavent information.

The option to pre order will be given before the release date This will be limited to about 20 units. Take a note of email address: preorder@eldavinci.com

Just out of interest, what would you expect to pay for a high quality GG? At the same time we want to be competitive but we must allow for the cost of process, seals and design which make the glass what it is. The GG will be guaranteed for probably 2 years. This will be finalised.

Hi Tony,

I would like to try the BK7. The size is 95mm diameter with centre hole exactly the same size as the centre hole of a CDR. I think its exactly 15mm. But can't be sure. Can you check if that is correct. I need it to be roughly 4mm or 5mm being max as any thinner it may break. If the price including shipping is good, I would like to order 2 of each, i.e. 2 disk with the wax and 2 black disks. Please get back to me with the price including shipping. Do give me the best offer you can as I would at the same time do a test run for you with my mini35.

Alex.

My disks from Ohara in Japan have been BK7 so I can say the material works.

Your choice of 90mm? That may leave you a little tight on two corners of your movie frame if you are using a CD motor and hub to run the disk. I looked at the smaller than CD-R sized disks and ruled them out for that reason

Your choice for disks may also be a little too thick. I use disks which start out at 1.3mm thickness but come down to 0.9mm by the time they are figured, polished and then one side groundglassed.

Thicker may make them less likely to break but too thick and some nasty optical things may start to happen.

I have found I can fit a 36x24mm image onto a disk of 87mm dia. The SGpro uses a slightly bigger frame then this with a disk diameter of 93mm.

Hi Bob,

Thanks for the info. How do you get your disk? You order online? 90mm was what I started with and with my MX500, it was ok. Upping it by 5mm should give me extra room for filming.

By the way, I wrote to you before if you remember and you sent me some info on your Agus mini35 plan. I assume you are using spinning GG. Or have you moved towards vibrating GG instead.

Now I know this has been discussed before somewhere but may not be in details. But does anyone know how P+S vibrate their GG. I have done one before where I used a DIY vibrating motor to vibrate a focus screen on a bracket setup made out of plexiglass. Unfortunately the vibration was so loud the noise would just get recorded. I scraped the idea. You think by using a proper vibrating motor instead of a DIY one, it could reduce the sound considerably?

Regarding my question about vibrating GG. Its ok, I search the site and tons of info.

Sorry I haven't got to you, I've caught a chest infection off of my daughter so I'm having lots of sleep and Tramadol (wonder painkiller) and antibiotics which knock you out.

The thickness glass we use is 0.56mm (a tiny touch over half a mm) this is OK to use with the diameters that we use, so long as the diameter is within a certain ratio to the thickness you should have no problems. But bear in mind, and adaquate seal and O-rings are needed to add additional support to the glass and to reduce to risk of fracture.

NOTE TO GG DIY'ERS: When sandwiching 2 pieces of glass together make sure that you make some kind of seal to ensure no glass separation occurs otherwise you'll have more then just 2 pieces of glass.

The seal for the rotating adapter mount has been designed to accept a 36 x 24 image frame.

Alex - I take it that you are requesting glass to make a GG and not a specific GG. Email me at the address below with your requirements and I'll get a quotation put together for you. Please specify material, internal and external diameter, thickness and quantity.

I'm back off to bed cos the screen is making my head pound.

Many Thanks,

Stephen - I will reply to your email possibly tomorrow. Haven't forgotten just lots on and not feeling to great.

REPLY

I did not progress to another method of moving the groundglass. Using something else other than a disk makes sense as a lot of groundglass arrea is inefficiently wasted with a spinning disk just to get a movie frame sized image.

The upside with a CD sized groundglass is that it is very simple. The rotating speed does not have to be fast because the linear surface speed of the disk even halfway in to the centre is quite fast for a given RPM.

This means very little vibration. Even with my single 1.5v battery 3/4 flat, the disk speed is fast enough to de-resolve the groundglass texture. On the other hand, an oscillating, orbiting or random vibrating groundglass movement can use a much smaller piece of glass.

However to get eough linear surface speed to de-resolve the groundglass texture, the cycle of movement must be much faster. Because the mechanical principle is not balanced in its nature, vibration will occur.

Three main methods of reducing the vibration are desirable,

---- make the groundglass area as small as possible to keep moving mass to a minimum, barely larger than the image frame, which can cause problems with picking up an edge in the image,

---- adding counter-mass to the mechanism which requires very precise engineering,

---- making the excursion of the groundglass as small as possible to reduce the actual motion of mass to its practical minimum and reducing the amount of countermass needed for balancing, which introduces a problem of needing the vibration of cycle of movement to be even faster for the linear surface speed to be maintained, another precision engineering process.

The upside is that all devices not using a spinning disk can be much smaller and lighter and the use of the groundglass material itself is more efficient.

Method of moving the groundlass in the P+S is according to their own literature as I comprehend it, several half cranks with small vee pulleys on them, driven by a common rubber belt by a electric motor.

This requires very precise engineering indeed. Counterweights can be added to the cranks but I don't know if anyone has bothered.

Keeping the movement very small and fast without adding counterweights and adding countermass in the form of a heavy housing is nearly as good a method and less complicated. But the appliance is then heavier than it should be and there is vibration still to be felt and heard.

Quyen's Letus35 as I understand it uses a different mechanical principle. It is elegently simple and requires fewer precision moving parts. Providing the flexible mounts on the pillars or sticks remain located as installed, there should not be movement of the groundglass off the focal plane due to wear. Vibration remains an issue as with the other methods and Quyen's passive method of moving the groundglass by onboard eccentric mass alone cannot be counterbalanced or the movement itself must fail. Counterbalance could be achieved with a second synchonous motor and contra-rotating counterweight mounted to the case however this would be an impracticable and diffucult system to engineer. Countermass is the only damping method that can be applied. However given there are only the motor bearings themselves which can wear, and there being a constant radial load being applied, there are about between nine and twelve fewer potential sources of future noise due to mechanical wear than in the other more complex methods using cranks.

The simple CD-R sized disk and CD player motor provides a very cheap, simple and reliable method of moving a groundglass. It is the groundglass itself which proves to be the most expensive item if real glass is used.

Making your own glass disk is a very hard task. If Tony Ralph can get his method up and running with an equivalent to an AO5 finish consistently around the groundglass, I would be inclined to buy that in rather than making my own. Getting my own groundglasses made and inventing the method cost me a 70% loss rate until I got the method sorted.

END OF REPLY THIS QUESTION


The tumbler method ("cement mixer") of dressing the glasses is a viable backyard method but not anywhere near the best. While a unifrom finish around the entire disk can be achieved with difficulty, getting a dead flat shape across the disk is another matter.

While my disks flicker or show grain effects little more if any than P+S products, they do move the image ever so slightly due to uneven shaping across the faces which cannot be controlled in a tumbler.

I do not know what went horribly wrong with the post above but it is mutilated and stunted and missing a bit about the polishing.

For the polishing there are first two grinds, the first with a farly coarse 300, then a finer dressing with the A05.

The polish is done by using a fine felt material glued down over a glass disk which is a tight fit in the bottom of the mixer barrel. The BK7 disk still glued down to the brass disk with wax, is moved over this pad in a slurry of cerium oxide. The polish happens in about one hour but if the grinding stages was not finished, the polish has very smooth fine pits in it.

When the polish is complete on both sides, one side is then dressed again with the AO5 against a glass disk to get the groundglass finish. Care has to be taken not to let the AO5 slurry to become too overworked as gouges can occur in the groundglass finish.

Finally, the preceding post describes my own understanding of how the other methods of moving groundglass work and may not reflect in truth the operating principles, so the my commentary should be regarded with some healthy scepticism. If My understanding severely misdescribes the principles of other appliances, then I sincerely apologise in advance.

Hi Bob, thanks for theinfo. Very informative especially on the P+S system. So looks like they too use a simple albeit more sophisticated system to move their GG. I 100% agree with you on the GG. If they are the best you can get, we pretty much solve the problem with image quality whether its rotating or vibrating. I admit I still prefer rotating as they are silent and no vibration as long as the GG is centrally located.

About your method of grinding. I am stump as to the complexity of the device. And looks like for the disk from Ohara, boths sides are not polished. That would mean you have to polish both sides. Getting one side to ground properly is hard enough. To polish it, wow, that is hard work.

I just use simple round cut glass and ground one side with 1200 sandpaper. The image look pretty decent.

I am hoping for a miracle with Tony's idea. If it work, then at least I can spend more time building a proper housing for my mini35. Making it out of plumbing stuff just isn't right as the precision is not there.

Once again Bob, thanks for the info. I am clear now on how P+S works.

Tony,

Hope you get well soon. I have just emailed you on my requirements. Hope you can give me a good offer. Once I accept, how do I pay you?

The ohara glass is definitely not finished on either side and involves a lot of work.

Tony's method of using very thin, very flat slices of BK7 finished glass is the attraction. There should not be any image shake which is nearly as much as a challenge to mpg2 compression as visible moving groundglass grain is.

What his method of finish offers is that one will be able to use a much larger zoom range in the relay stage with FX1 or similar inbuilt lens camcorders to go in closer on the groundglass image to assist framing and composition without compromising the image sharpness as much.

This is why I would still use his glass as a spinner and not simply as a fixed glass. Viewed close enough and there will have to be some texture visible as there is with wax.

But used as a moving GG, the main limitation on zoom-in enlargement of the GG image may well be the sharpness of the SLR lens itself and the camcorder's own limitations.

If only he can get the texture uniform around the entire disk??

Tony,

You feeling much better? This thread hasn't been updated for a few days, thought I'll just checkup on you.

Hi everyone.

Sorry I havent updated you all on the DiGi35 GG, I've just got back from holiday. Website should be up and running next week with footage and stills. To all of those who requested a brochure, that to will also be complete by next week.