In a serious production environment, I would not use the on-camera mike except to create a reference audio track for syncing up later to a separate double-system audio recording.


Of course your wouldn't. And of course no one should.

You just mentioned the only thing an on-camera mike should be used for, which is for reference audio.

Double-system is indeed the best way to go.

"The Cage" wrapped today with a good fight scene where Justin is mobbed by three thugs on his way from the train station. Of course he puts them onto the ground in a state of disintegrity.

My shadow footage was not so good today. I was using the 12mm-24mm Nikon lens to enable wide-angle coverage from the boom swinger's position when opportunity permitted. That was my primary occupation for the day. The lighting became a thin high light overcast.

This is the condition which aggravates any flickering tendency with this lens. I had also changed the design and perhaps should have left best alone until this project was complete as the behaviour of the appliance has changed, for the better in some respects, worse in others.

I adapted the old appliance to fit the JVC HD100 on front of the standard lens. The 82mm filter mount on the lens appears to be metal but I think it is plastic. It is not ideal as the 0.7mm thread is easy to crossthread and damage. Some sort of quick release arnangement would be better.

I tried a clamping style of mount onto the lens hood mount around the outside but this causes interruption to the movement of the focus adjustment as the mount distorts enough under compression to bind on the lens body.

The Century Optics +7 dioptre workson front of the standard Fujinon lens but the zone of available sharp focus range onto the groundglass is very much narrower than for the PD150 and FX1.

I think it may be because the focus adjusment physically moves the front of the standard lens forward or backwards and the dioptre moves with it. An image of sharpness comparable to the FX1 ca be had.

Certain combinations of primary focus, camera lens backfocus and zoom can cause the outer zones of the image to become soft in the relay stage. It also performs better if the groundglass image is framed somewhere near midway between the 24mm wide image and the 30mm wide image.

The camera owner also has Les Bosher's Nikon SLR lens adaptor. So we tried the 14mm Sigma f2.8 and the Sigma 20mm f1.8. These work well on it as alternatives to a wide adaptor on front of the standard Fujinon.

The Nikon lens locking pin release button on Les Bosher's adaptor is initially baulky but with practice becomes easy to operate.

The long and arduous road of post-production now begins.

The JVC HD100 camera has been trouble free for the entire shoot. It now goes apparently offshore on another documentary adventure.

"The Cage" hopefully reaches completion in about 6 months time.

Hi all,

Wow! its been a long time since I last posted here and to be honest not sure how much I have missed. Great to be back though. Anyway, if it isn't old story yet, I managed to finish my mini35 using rotating ground glass instead of ground CD. Will be testing the device and see how the video turns out. I left this project in my drawer as I couldn't get a good ground cd. Just a week ago, my bro got excited about videocam and how to get the film DOF look. I told him I had the mini35 built a year ago and its left in my drawer. I took it out and just out of the blue, the idea of getting a round piece of clear glass sprung to mind. I bought the disc today (its off a cheap table clock) and grounded it and it tested well without my DVcam. My DVcam is in the shop due to defective CCDs. I will be posting some pic here in the next couple of days and see if anyone has any comments.

Lately I have looked at two alternatives to the P+S mini35. Its the M@ or Micro35 from REDROCK.COM and the one from GUERILLA35.COM. I think the M2 is much better at USD995. Anyone has any comments on these two mini35? I wouldn't mind getting a set as it is properly built.

For the wider prisms, I found that in being able to go a little wider with the zoom, that the camcorder is now too low by about 1.5mm and picks up the edge of the groundglass disk in the corners.

Moving the camcorder lens axis 1.5mm to 2mm vertically brings the bayonet mount into the edge of the pipe cap which has to have a clearance cut away. The inner face of the cap also has to be kept about 2.5mm out from the image tube end otherwise the bayonet fitting fouls against it.

The SLR lens mount may have to be moved the same amount downwards to compensate for the shift if the SLR lens centre is already too high.

If the SLR lens mount centre was originally correct, the 1.5mm does not seem to make much difference unless you want to go really wide and live with the corner falloff or bury it with dark image areas.

The disk in the new device is a rework of an old glass disk which got scratched on the end of a self-tapping screw in the prsim block which I forgot to trim off.

The aluminium oxide 5 micron was overworked but this time no partial backpolish was done. This seems to cost apparent resolution but the return from the Lemac chart is the same for the backpolished version.

I think this is due to the wider frame now available off the groundglass for the same framing into the camera of the chart.

Hi Bob,

Looks like you have managed to make the image upright. Any shots of your mini35? Would like to see how you manage to do it. I have done one as well using the mirror and prism of an SLR camera. I built a casing out of plumbing pipe end caps. The only problem is that the image is so small and my DV cam has to zoom in so much that the angle of view is reduced. I think I may need to use a wide angle lens to compensate for this but have not tried as i don't have a wide angle lens.

Alex.

The field of view available from the SLR camera viewfinder is really too small. As you mention by the time you get zoomed in past the confining edges of your prism/optical path all you have left is a very small centre image.

My current version uses the following :-

Nikon f1.8 lens >> groundglass >> two x 45mm x 45mm x 62.8mm prisms of 32mm common thickness across all faces. These are set up like porrorprisms in binoculars. >> 7+ Century Optics achromatic dioptre >> camcorder.

The prisms sit in 90 degree opposition which flips the image. One half of the hypotenuse of one prism covers one half of the hypotenuse face of the other. The uncovered half of one prism lets the image in. The uncovered half of the other prism lets the inverted image out.

The prisms are clamped onto a cylindrical shaped block about 10mm thick and rest in channels milled out of the block which is phenolic board.

The cylindrical block prism combination will just fit inside a 100mm PVC pipe and still allow the fit of a Nikon lens mount on one pipe cap at the front end and the camcorder lens hood mount on another pipe cap at the rear end, to fit and still allow true parallel centrelines from SLR lens to camcorder lens.

The FX1 lens hood mount has to be hard against the edge of the cap and about a 0.7mm clearance has to be milled or engraved out of the inside cylindrical surface of the cap to allow the bayonet lug to turn as the camcorder is mounted to the device.

I have not yet redrafted the design to show the new parts. I had the old 40mm x 40mm x 56mm x 40mm common thickness prism design up at savefile.com as a .pdf file but it might have timed out by now. If you want the old design as a general principle guide, send me an email with an email address I can send an attached file to and I'll send it.

The design uses a full CD sized disk. The outer edge comes within 0.5mm of the side of one of the prisms.

Hi Bob,

Thanks for the explanation. I have just emailed you with my email address. Thanks for the info.

Alex

They had the wrap party for "The Cage" in Nedlands tonight (last night actually). I think there may be a few sore heads and some late risers well after the sun comes up.

They have assembled a quick trailer for the party and althoug it was at much lower res than HDV and it was framed small on the projection screen, the action was a treat to watch.

I also got to see some of the "special features" footage I have been shooting on the modified AGUS35 projected on a large wall for the first time.

At its best it looks good and seems as sharp as direct-to-camera origination but has much less contrast and faded colours. However, when the SLR camera lens focus is even slightly off, at projection magnification, it then looks dreadful.

The flicker which comes from using the 12mm-24mm f4 Nikon in a bright high-contrast outdoors environment was much less apparent and the image from this was surprisingly sharp, given that it is a zoom lens.

What also became very apparent as that some footage shot with the same lens, groundglass and camcorder combination but of a smaller 24mm image off the groundglass was much softer as projection than later footage shot from a wider 30mm image after I had replaced the prism block.

I don't see the sharpness in the image. The idea of the adapter is to have a sharp image as you do when not using the adapter, but yet have the ability to control the D.O.F. I don't see the sharpness in your image, perhaps it has to do with the the fact that we are seeing it on the computer screen.



Brett,

We are all interest, show up the design.

Btw, i have been editing the footage of my short feature, and damnit looks awesome...

Here are some pics.

http://altoque.tv/35mmAdapter/DE35MM19.jpg
http://altoque.tv/35mmAdapter/DE35MM18.jpg
http://altoque.tv/35mmAdapter/DE35MM17.jpg
http://altoque.tv/35mmAdapter/DE35MM16.jpg
http://altoque.tv/35mmAdapter/DE35MM15.jpg
http://altoque.tv/35mmAdapter/DE35MM14.jpg
http://altoque.tv/35mmAdapter/DE35MM13.jpg
http://altoque.tv/35mmAdapter/DE35MM12.jpg
http://altoque.tv/35mmAdapter/DE35MM11.jpg
http://altoque.tv/35mmAdapter/DE35MM10.jpg
http://altoque.tv/35mmAdapter/DE35MM9.jpg
http://altoque.tv/35mmAdapter/DE35MM8.jpg
http://altoque.tv/35mmAdapter/DE35MM7.jpg
http://altoque.tv/35mmAdapter/DE35MM6.jpg
http://altoque.tv/35mmAdapter/DE35MM5.jpg
http://altoque.tv/35mmAdapter/DE35MM4.jpg
http://altoque.tv/35mmAdapter/DE35MM3.jpg
http://altoque.tv/35mmAdapter/DE35MM2.jpg
http://altoque.tv/35mmAdapter/DE35MM1.jpg

It looks to me as if either the GG-to-35mm lens distance is off, or the 35mm lens being used is extremely soft at the aperture settings being used.

double post

I am a little confused.

Those are not any images I have posted anywhere. I may have also confused others with my post above.

In terms of sharpness, I should have used the words, "seemed as apparently as sharp as". This is because the footage was transcoded to MiniDV and letterboxed from the camera playback and dubbed straight to a DVD recorder.

The disk from this was played into a video projector so it is not a path which would show differences in sharpness at HDV resolution.

At its best it seems apparently as sharp. The flashing effect of thin bright highlights against dark backgrounds which happen when the camera is handheld on a fixed subject mostly goes away with relayed imaging.

Bob, we're talking about Agus' pics.

Slightly off-topic but references a few posts back in this thread is a low-no budget feature project titled "The Cage" which I have lent a bit of a helping hand to by holding the odd boom pole now and then and shooting some background extras footage for a "Special Features" for their intended DVD-Video release.

For those who may be interested, they have just posted a trailer which was prepared for the wrap party and this apparently is located at the following web address.

http://www.youtube.com/watch?v=hSPQnV2vH8I

I don't know if this here is a clickable link. I don't have the knowing of all that haitch ref stuff which makes the web addresses switch through.

I am enquiring with Ohara in Japan to see if they are still making the cut blanks of CD-R sized optical glass disks with 15mm center hole, 1.3mm unfinished thickness.

Is there anyone else making their own from unfinished blanks?

Bob,

Yes, im having 1.2mm thick toughened glass blanks made. 6mm centre hole, 86mm outer diameter.

Wayne.

If it is not a trade secret best kept, can you advise per unit cost of your raw disks? Would your source be able to make to standard CD-R disk size.

Have you had any problem with the groundglass finish causing outer circumference stress risers in the glass. My disks came with chamfered edges which are apparently a necessary part of the process. I found I had to maintain the chamfers as the disk wore down to 0.9mm in figuring and dressing.

The disks also ring like a bell once they are dressed.

The Ohara disks are S-BSL7, outer and inner circumferences concentric, (they make glass substrates for hard disk drives) capable of a fine GG finish but were AU$50 per unit to Australia in 2004. I am awaiting advice on availablility.

My original enquiry to Ohara was for finished hard drive substrates which would have been ideal and by coincidence, closer to your disk size but for one small issue, the glass is not transparent.

In the end I decided to go with the original CD-R size to keep things simple and to allow higher shutter speeds relative to disk rpm, but Ohara could have supplied smaller had I requested then in 2004.

Bob,

If you can email me at info@sgpro.co.uk, maybe we can sort something out.

If anyone is using the tumbler method of making their own groundglass disks, there is a reasonable fix for the uneven finish problem. It seems the glass disk on which the groundglass disk is ground against, tends to pick up and rotate which messes up the continuiuty of the cycle.

So far with the first AO300 stage where raw disks are figured into shape and smoothness, a piece of automotive tyre inner tube, cut to the diameter of the tumbler barrel, placed between the grinding glass and the bottom of the tumbler barrel seems to cause enough grip to stop the problem.

If it recurs with the finer grades which pick up with more force, I shall try a piece of a non-slip bathmat, you know the ones with the multitude of suckers on them.

Repeat of info.

For tumbler barrel 160mm internal diameter.
Disk diameter 120mm approx.

For Grind - barrel is best at 60rpm.

For Polish on felt, - barrel is best at approx 90rpm. A little faster is okay as long as the platen does not start to swing or bounce inside.

Angle of inclination aprox 45 degrees.

If you make drive belts out of automotive inner tube, put one internal twist in them, (one end inside out not simply crossed over). they run longer and better.

Furthur on the tumbler method.

Best results after stabilising the glass grinding disk seem to come from tilting the barrel up to about 30 degrees off horizontal and putting more slurry in which seems to take a little weight off the platen but it doesn't jump about.

Results so far with the AO5 micron grind seem to be that the groundglass finish is denser than previously, flicker problem is gone but resolution is not as good.

Aperture of f8 can be used on the ultrawide lenses in low contrast lighting conditions without flicker or groundglass artifacts. The disk figuring from raw disks is also better.

The glass grinding disks turn out to cause another problem. The grind now goes out uniformly to the edge of the optical disk whereas previously with the shallower tilt, most of the grind seemed to be happening in the centre. This now causes a distinct ridge to build on the edge of the grinding suface where the optical disk being dressed does not touch it.

When separating the two glass disks at completion of a stage, care has to be taken not to allow the ridge to brush across the ground finish as it scratches or sweeps a wider area clean of groundglass texture.

Hi Bob,

Great to read that you are still working on GG preparation using the tumbler system. But I am very curious, have you looked into using focusing screen as a GG as others have done? Or you are onto something here with the tumbler and grinding system. I felt its just too much work to prepare a GG from rough cut round glass to polish and then to GG. I have been meaning to ask you this a long time ago but felt I kept it long enough and my curiosity just wouldn't keep me quiet. Sorry in advance for being so nosy.

I understand you have done a mini35 of your own, any chance of seeing some pics and video?

Alex.

The home grinding of disks happened because I could not get CD-R sized disks which were glass, thin enough, with a correctly centred 15mm hole, already finished.

At the time, the Ohara disks from Japan were the only source I could find, though I have since been advised Knight Optical in the UK can do them complete.

As I have learned things, most of the glass disks have had several re-works done on them.

Because I have used full CD-R sized disks and my design is built around them, I have not explored the focussing screens.

There is I think a .jpg of the non-erecting and erecting versions of my sewer pipe based device as www.dvinfo.net/media/hart

This folder is in bad need of housekeeping. The files there are a non-systematic accummulation from when I first started experimenting with the idea. I'll have a look there and see if I can find the .jpg name and edit this post.

Alex.

Dvinfo edit timed out and I could not correct the post above.

I couldn't find a .jpg of the erecting "flip" version. There is an image of the earlier version at this address -

http://www.dvinfo.net/media/hart/Aguscam.jpg


Don't attempt to build to any of my .pdf designs. They should be regarded as conceptual only as things have moved on since they were posted.

Bob,

thanks for the direction. Checked out the files. I liked the picture with the oranges on the branch. The color is nice. Not too sharp nor soft. But on other pictures, they are a bit soft and have some hazy feel probably due to light reflecting off inside the Agus35. Not sure how to avoid this though. But generally, the image is nice. Saw the tumbler. Wow, thats alot of work creating the thing. And it really spin very fast too.

Personally, I have at this moment given up the idea of using spinning disk as I couldn't get the right materials to even start. So now I am working on something along the line of Letus35. Design is done and just need to send off to the CNC shop for prototype fabrication. Hopefully can showcase it here in a couple of months time. Using focusing screen, flipped and has rail supports. Won't say anymore and I will wait until its in my hand and I have tested it with some video sample. If nothing great comes out of this, I will shelf the whole idea and buy one thats in the market now. Fingers crossed.

Alex.

The oranges images are probably closest to where my current efforts are at. That particular groundglass disk was the very best I ever did and I have not been able to replicate it since although the last one I have just done comes close. The original got broken at an airshow over a year ago.

Some of the "smoky" images I think were the ones shot through a stack of Hoya close-up lenses 1+, 2+, & 4+ , which yields an inferior image due to bad chomatic distortion. These lenses were never intended to be abused in such a manner.

If your design is close to Quyens in physical size and groundglass image size, my guess and it is only a wild guess, is that you would need something like a +5 achromatic dioptre on front of a camcorder zoom lens setting of between 45mm and 55mm.

Going by the size of his mirrors, the focal point of a +7 might fall short of the distance between the GG and the front of camcorder to get a sharp focus on the GG.

Quyen's implementation is a valid one and the design inherently dampens against noise and vibration. If you have access to CAD design and machining, then you are fortunate.

Interestingly, Quyen's flip design uses larger mirrors than my experiments. It seems he has done this to enable the mirror paths to be oriented at 45 degrees to preserve the prime lens and relay optical centres on a vertical centerline, whereas mine is offset low and to left.

The groundglass is much smaller than a CD-R disk sized groundglass and represents good economic use of materials.

My personal preference would be for the groundglass excursion to be more like 3mm to de-resolve any dust specks which get onto the GG but that would also shake the crap out of any adaptor or cam attached.

The excursion must be orbital, not linear. If linear there will be periodic frames where the groundglass texture becomes visible due to the frames syncing up with the halt at reversal of direction.

While it is very inconvenient to design in, you need to make sure you have facility to accurately set the correct backfocus for the SLR lens on front and that the groundglass is perfectly aligned at right angle across the optical centerline or can be adjusted to this accuracy.

Its not so critical for 50mm or longer focal lengths. However for wides and ultra-wides, if the backfocus or alignment is off, these lenses will not perform at wide apertures or have a soft area somewhere in the image which will not sharpen with moving the lens focus ring.

Some of the modern lenses which are full film frame but also optimised for digital SLRs seem to have better performance related to light distribution across the GG.

The Sigma 14mm f2.8 seems to stop tighter to f8 - f11 without showing the grain in certain lighting conditions. But this might also be my imagination.


Good luck with your endeavours. If ever you encounter a legal practitioner in Brunei by name of Colin Clarke, please pass on my regards.

Another little best practice issue has arisen with using platens in a tumbler and wax to mount the raw disk to them.

There is enough flex in the glass disks, especially after they have been partially processed and have become thinner, they will distort between two mountings and no longer present an entire surface contact with the grinding surface.

If the disk is unmounted then remounted before the next stage of finer grit is done, there will be caused a variable density of texture around the disk. It is enough to cause a flicker problem.

Best practice therefore is to keep the disk mounted on its platen and change the grade of the grinding material, rather than swapping several disks across a single grade. I have only one platen. The obvious solution is to make a few more.

Another handy trick for reducing wax contamination of the dressed surface after boiling the disk off the platen and lifting the disk off, is to fill a sink with hot water and place the boiled pot into the sink and allow the hot water to overflow into the pot.

Slowly run cold water into the sink. Presently, the wax on the surface will set in thin sheets and can be skimmed off. As the water cools, the disk can then be brought out without wax particles setting on the ground surface. There will still be some but solvent based stain remover like Preen will lift most of it off.

I tried making another wax composite disk, this time by placing two ground disks face to face with wax in between and relying on the depth of the grind itself to determine the thickness of the wax. Again, the image is by far and away the sharpest but the variable density problem is still there.

The groundglass grain remains, but the evident contrast of the grain seems to be diminished. It seems to take another f stop of setting on the SLR lens to make it as evident but there was no science involved in this observation.

Brainpick Time.

In regard the Sony FX1 / Z1P PAL camera family, there is a function known as peaking. In the exposure I had to these cameras in getting an AGUS35 to work, I tried the function whilst setting up SLR lens backfocus after disturbing the appliance. I understand peaking to be a focussing aid.

Does peaking artificially enhance the apparent resolution of the image or does it represent the true output of the camera CCD before processing to HDV codec?

I ask this because when the peaking function is selected, the current groundglass I have battled with yields a defined return from the horizontal 850 TV line block on the Lemac test chart, this time without flicker.

When peaking is off, then a faint moire pattern is apparent in its place.

Which represents true resolution at the CCDs, peaking on or peaking off.

Any advice would be much appreciated.

My experiments suffered a bit of a setback tonight or maybe I found a reason for the resolution wall I have hit.

I have up until now reasoned that the limit on the image area off the groundglass had been determined by the available aperture of the prism path at the front face mounting point and true this can be.

However I have since discovered that the optical arrangement I use causes the aperture edges at the rear face prism mounting point to encroach into the image.

By the time I zoom past it, the recovered image off the GG is only about 22mm wide. Ironically, this ends up close to what I understand the P+S Technik to be which is 21mm corner to corner. So I have been chasing shadows for some considerable time and not knowing it.

The arrangement as it is remains quite usable and is a close couple to the camcorder bayonet mount which enables handheld work.

If I use a 4+ dioptre in place of the +7, I get back most of the 28mm at penalty of having to add 45mm to the body to move the GG furthur forward. this adds an uncomfortable leverage to affect the front of the camera body.

camera: dvx100 original
GG: old scratched frosted cd I found in the trash on scrap cd-motor
macro: Generic macro lens from .45x wide angle lens
approx distance from macro to GG: 60mm
lens: Nikkor 50mm Micro Lens

Here's the footage: http://www.schtm.com/cheap35/cheap35.html

You need flash to view it.

I shot it at night in my bedroom so don't expect pro lighting.

Everything is inside a project box I got at Fry's.
Going to start working on a DIY rod system next..

It's always good to see this thread brought up :)
I think somebody should bump it up at least once a month or even make it a sticker so the newer DVinfo generation can see how it started and who started it before people started to run away with his concepts and efforts, which were a fruit of generosity, innocence of sharing and group collaboration, and turn it into enterprises.

Ave Agus!

Back to the honest original AGUS35 and probably still the best in terms of cost benefit and personal satisfaction, with yet 85% or better of potential performance from scratch.

The Micro-Nikkor may be a bit tight if it is a f3.5 but is otherwise a good lens with nice close-up ability and well chosen for a starter project.

Welcome to the obsession and enjoy.

(Probably about time somebody made a documentary because the subject surely now has a life of its own.).

Is the easiest way to find frosted plastic cds still searching many different cd-r packs?

Sheldon.

I think you are better off getting a clear one and putting the groundglass finish on it. The frosted CDs may have the diffusion effect for the full thickness of the disk therefore resolution and low light performance may be disappointing.

For clear blanks or the frosted ones, try duplication houses or local video production outfits who burn a lot of DVDs for wedding videos, commercial TV advertisements and the like or CD-Rs for multimedia.

Clear DVDs and CD-Rs out of retail packs these days seem to be two types, a special moulded spacer or partially completed disks diverted from production which can be seen to have a fine pattern of lines on them.

Diverted disks will run true but are now resistent to good groundlgass textures being ground onto them as they have a scratch resistant quality to them.

Alright, I don't have access to a tumbler- but I can get sandpaper up to 1500 grit from an auto store. What grit should I get? Can I use any blunt hard object to sand it down? How long should I rub it?

Sheldon,

The good news is a tumbler is only a help for lazy people like me. It enables you to conserve and not waste the abrasives as they are contained in use and can be poured off afterwards into a pasta sauce jar for storage and re-use.

Hand-finishing nearly always wastes the entire abrasive solution but you need much less of it at a time.

The tumbler is also useless for the newer scratch resistant blank or clear disks.

For a start, I would probably go with a 600 grade if you are going to use an abrasive sheet. A 1500 paper will probably clog and it will be difficult to get a good uniform graded finish across the entire disk area.

Wet sanding would be the method. Dry sanding will clog the paper and then a big piece of grit will come off and dig a long scratch across your disk.

Sanding with a sheet in any event is going to give you lots of scratches not small pits.

The sanded disk will give you good diffusion but lots of light loss and inferior definition. To get pits you need to use a loose abrasive in a water slurry.

If you can find a big enough piece of double-sided adhesive sheet to glue the disk down onto a flat surface, it is helpful to avoid bending the disk and protecting the clear surface. You need to remove the ridge in the centre section of the disk for this to work if you are fixing the disk down.

Otherwise, stick-on plastic material like schoolbook covering or cheap thin wood pattern style plastic sheet will last long enough in the water to protect the clear surface.

To avoid localised areas of varied finish, it is best to mount the disk onto a firm surface and use the whole disk like a sanding block. You will find progress is painfully slow compared to being able to add pressure to smaller areas on the disk.

How you rub the disk is up to you. I think most hand-finishers are moving the disk on a flat surface rather than fixing the disk and moving an abrasive surface over it.

To get a good grade across the disk you will also need to shave off the ridge which is near the hub centre on the disk. You will find a small piece of break-off parcel knife the handiest for this task used almost upright as a scraper.

Work on the ridge from the opposite side across the disk - more easily controllable.

If you use a loose slurry to dress the disk, the base surface on which you grind it can be sheet glass. You can get abrasive material from lapidary suppliers (gemstone hobby suppliers) as silicon carbide grits.

There is another dry method you can use to get a pitted finish and is not grade dependent. You could use 80 grit paper if you wanted but with care to avoid scratching.

You need to have a stick on backing to protect the clear surface of the disk. You place a sheet of abrasive paper on the disk which sits on a hard flat surface. You then use something to press the grit on the paper hard into the disk to cause pits.

This can be the back end of a BIC pen, but better is the hard round end of an automotive pushrod, either engine valve train or clutch, engine valvetrain pushrod is better.

You have to prevent the paper from sliding on the disk which will cause scratches. You have to periodically move the paper so the pressed pattern is changed.

The rubbing action will eventually wear away the paper. Wet and Dry silocon carbide paper is more robust in this regard.

Another method of applying localised heavy pressure is to get an old bearing race which remains free, fix some sort of axle through it and to use this arrangement like a wheel to roll across the paper. You have to use it raised onto on the corner to generate enough pressure.

Another method is to steal the kid's marbles and place them onto the paper and roll them about with a thick piece of hardboard. They will scratch and chip under pressure so a bunch of steel bearing balls is better.

They also need to be contained by someting like a small steel pie tray or cutdown metal can.

It is a long and arduous process before all the very narrow tracks drawn across the disk evenutally join together to form an even grade, but an acceptable result can be had. This pressing method also deals with the problem of scratch resistant disks.

Blow off but do not wipe off the loose dust on the disk. If you touch the surface at all it will be spoiled and will flicker like crazy.

Before I saw your reply, I picked up a palm sander on sale for 9.99 at Kragen's, attached some 1000 grit sand paper, sprayed water, and appled pressure to the side of a clear disc that I wanted to grind. I set the disc on a big piece of double-faced adhesive paper. The results were great!

The only problem is a flicker at 1/48th shutterspeed-- if I move it up to 1/24th, then its flicker-free/crystal clear.

I'll try one of your methods (most likely the BIC pen method), or at least refrain from touching the ground side after sanding it-- maybe I can reduce the flicker at 1/48 shutterspeed.

Your wet sanding method may yield an easier result than the back of a BIC pen. The pressing method is really long, hard and arduous and you will still get some flicker.

When wet sanding, try to keep the motion in a short circular pattern so the pattern of scratches is a uniform angle across the image frame at any point around the disk.

I gave up on prressing the disks because of shoulder soreness after two disks and used a alternator bearing with a bolt stuck through it for the third then went to dressing in a grit slurry.

Ways of minimising if not eliminating flicker entirely are :-

Set camera automatic gain or automatic exposure levels to manual or slow so the camera does not hunt for the exposure as the disk turns through brighter and darker segments. It makes the flicker look worse.

Shutter speed at 1/60th sec in NTSC land for 60i?

Try to run the disk close to if not exactly on 3600rpm. With a normal CD motor you will probably need about 4.5 volts to get this and the life of the motor may be shortened.

They normally run in continuous duty at lower rpm driving the disk or if used in load-unload actuators or tracking systems, they run faster but in short bursts.

On or very close to 3600rpm, the same piece of disk will pass the camera viewpoint or advance or trail very slowly which will minimise the flicker effect which may only be seen as a slow cyclic rise and fall of brightness, depending on how out of sync with the frame rate the disk rpm is.

If the cyclic rate is really slow, you might try automatic gain on the camera which might then improve things.

You could try 1800rpm but you will likely see a flicker nearly in phase with the interlace fields which may make it look worse.

With 24P I'm not sure how this will work out. My guess is to try as close as you can get to 1440rpm. 1.5 volts will get you close. If there is flicker in 24P try doubling the disk speed to as close to 2880rpm as you can get it.

Flicker tendencies are aggravated by high outdoors contrasts and lighting from behind. Light bright overcast really makes it look bad.

Wayne and Dennis.

If you get a chance to get your hands on one, try the Sigma 50mm-500mm f4 - f6.3 zoom on your devices. With your good groundglasses able to go tighter than f5.6, I think you will be well pleased with what you see.

Up until now, I have used the Sigma into the camcorder with the groundglass removed for ground-to-air shots of aircraft in flight. The image is sharp but I have had to zoom the camcorder right in to get inside the vignette of the big lens in aerial image mode. The big lens also has to be used wide-open which reduces sharpness.

Additionally, the ND filter has to be constantly ridden as things seem to be more sensitive to this feature. The PD150 and FX1 camcorder are best left on auto which is not the ideal way to do things.

In aerial image, the lens interacts conveniently with the autofocus but the autofocus can run away unpredictably if a bird or insect flies through the shot at a close distance. The autofocus then goes for the nearest sharpest object which is the back of the Sigma lens.

With the groundglass fitted, the vignette goes away. The shot can be wider. Corner falloff occurs but furthur out in the image than the vignette, but the bonus is that the other problems all go away as well.

The little bit of resolution loss you take with the groundglass is offset by being able to back off on the camcorder zoom a little and being able to close the Sigma lens down one or two stops to restore sharpness without provoking grain on the groundglass.

I have yet to try it against high light bright overcast which most provokes flicker from my groundglasses.

Except for having to cart this heavy assembly around, these things could be handy implements for wildlife work and sports videography. A tripod of course is a must unless you are built like big Arnie.

Furthur to above.

Some nice glary overcast and intermittent roll clouds came over so took the thing down to Jandakot and shot some real-world tests with light from behind against the cloud.

In these conditions, a little edge falloff is observed when camcorder zoom for relay is taken back past about 48mm.

The Sigma 50mm - 500mm lens at f11 will still yield a flicker free image but against a uniformly dull white glary background, groundglass artifacts appear in the form of faint whiter concentric arcs, no doubt due to inconstencies in my disk grinding method.

Going to tighter apertures on the Sigma and opening the camcorder aperture correspondingly to compensate, does not confer noticeable added sharpness to the image.

When the disk is turned off, the groundglass texture goes really dark brown like burned coffee powder.

There is little apparent difference between imaging through the adaptor with or without the groundglass except the reduced ability to pass light with the groundglass installed. An inspection of the images on a large screen is yet to happen and a different story may emerge.


Imaging path :-

Sigma f4 - f6.3 50mm - 500mm SLR lens >> AO5 moving GG >> 2 x right-angle prisms >> Century Optics 7+ Acromatic Dioptre >> Sony HDR FX1. Settings manual, shutter 1/50th sec, db video gain, relay zoom 48mm - 54mm, camcorder focus - auto. White-balance - manual to white card.

http://www.schtm.com/cheap35drew.html :)

I have attempted to upload some short demo shots from recent experiments including today at youtube. I have no idea if they successfully got where they should have. They seem to have and can be found at these addresses :-


http://www.youtube.com/watch?v=0CXz4oluTpA

which is a test of AGUS35 - SONY FX1 SIGMA f1.8 20mm @ f4


http://www.youtube.com/watch?v=EfC4V1iE-kk

which is a test of AGUS35 - SONY FX1 SIGMA Ff4-6.3 50mm-500mm @ f8


I don't think the resolution is going to be anything to write home about by the time the internet has finished with it.


FOOTNOTE:

I just managed to open them. don't waste your time. They look dreadful.


Sheldon.

I shall have to take some instruction from you on how to make these autoplay videos appear here.

I simply use Macromeida Flash 8 Professional. As of version 8, Macromedia has included an EXCELLENT video encoder that all the new flash-video sites (youtube, google video) use. You simply convert your video from any format to an "flv" file, import the flv file into a new flash project, and voila-- you have a page that'll play your video as long as you have the flash player. Just publish and upload the html, swf, and flv, and you'll have what you need done.

Here's another site for the two tests. They are in wmv9 coding out of PP2 so are not the sharpest examples in the block. One of these days when the cargo plane comes home and brings good things to the mountain top, I'll buy Quicktime for the H264 encoding capability. In meantime, this will have to do.


http://media.putfile.com/20mm-Sigma-f18

http://media.putfile.com/SIGMA-50-500-f4-63-LENS


Sheldon.

Thank you for your advice on Macromedia.



FOOTNOTE:

Sorry. Looks like this sucks comprehensively too. Doesn't work at all. Never did like trying to download video so I don't expect uploading to be any better an experience.

www.savefile.com was the only one that worked and it looks like that one has gone belly-up as I can no longer access the site.

Looks like its back to the .jpg frame grabs.

FURTHUR FOOTNOTE.

Savefile must have been down for some care and maintenance as it is back up again now. I shall send my tests there.

FURTHUR FURTHUR FOOTNOTE.

Savefile is still broken. I probably broke it through mismanaging the account soimehow.

My previous material there had all timed out and dropped off and I am now being asked to change to a new password but my current now redundent password is being rejected so I give up.

In cost benefit terms of time wasted, it is easier to burn and send DVDs by post than perservere with attempting to ram Mbits into the end of a 300m copper overhead pair landline when they don't want to go.

As yoong Albert's moom wunce sedd, "Boy I'm vexed".

I'll try and get some .jpgs up when I can work out how to unstretch the frame grabs from cineform captures.

http://www.schtm.com/kitchen.html :)

Tried again at savefile.com under a new account - no luck. My computer is a bit too old or the landline is too thin for fat files to fit through.

http://www.schtm.com/jungle.html
Can't believe I even considerd blowing 995 on the redrock

Hey Sheldon,
Have you tried the Nivea cream on your GG yet? That is supposed to yield some great results...

<QUOTE>http://www.schtm.com/jungle.html
Can't believe I even considerd blowing 995 on the redrock</QUOTE>
Hi Sheldon,

What did you mean?

I rented the redrock and got inferior results to the agus35 that I used to make the footage above.

oh man and ouch too! what a blow to redrock. Sorry but I am not trying to put anyone down here. Great effort from redrock by the way for a great product and creating a healthy competition, but I have always thought the footage from redrock aren't as great as I expected it to be. I hear alot of comments from people who had good results. But now my doubt is confirmed. I think its their GG. Some improvement probably in order.

Hey Sheldon,
Have you tried the Nivea cream on your GG yet? That is supposed to yield some great results...

Please forgive my ignorance, but what would exactly the Nivea cream do?