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Old May 18th, 2009, 11:43 AM   #1
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Another HFS10 SGBlade shoot to Cineform

Hi all,
I have been grinding away again to determine the best DIY Rotorazor.The last one I made was a bit too light fast but this time I made this one just a little bit faster than the Rotorazor 1.The results are worth it and
I am thinking of settling for this one.The colours are also so much more vibrant out the box so I did not even need to add saturation.Thanks to the model - Sarah a friend and again thanks to Wayne for the glass discs.
I am having such fun getting different looks.

This in my opinion makes the SGblade the most versatile of all the DOF adaptors - being able to go for different looks at will.

HFS10 SGBlade composite HD capture to cineform - Sarah on Vimeo

Download the Full HD version for best viewing.
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Old May 18th, 2009, 10:55 PM   #2
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Henry.


Try this one.

Grind one of your disks to a 5 micron aluminium oxide finish. Backpolish the sharp peaks of the grind finish with cerium oxide (used for final finish of lenses). You only backpolish just a mere trace. Too much and the bokeh looks like gummy eyes and like video.

Don't forget to maintain a chamfer around the sharp edge of the glass disk otherwise some chips may come off the corner, roll under and gouge your good work.

Against a scene without bright pinpoint higlights, if your camera autofocus hunts through the groundglass for the aerial image you may have gone too far.

Getting the backpolish even across the entire disk can be difficult unless you use some sort of machine or rub the disk itself across the polishing surface. To avoid bending and breaking my disks I supported them on a machined metal plate by mounting them with candlewax.

The method - shave some wax onto the metal plate with a cheese grater. Lay the disk on top. A slow cook over a stove top until the wax melts and creeps under the glass. Small bubbles don't matter. Gently slide the plate off the heat and let it cool in place. Remove disk of metal after finishing by boiling in a pot of water. Use a roasting skewer to slide the disk off the metal.

Don't pull the disk out into cold air as it will crack. Let it cool with the water in the pot. Wick the wax off the surface of the hot water with a paper towel. Toss in some household liquid detergent while the water is still hot. Cleaning the wax off the glass is a real chore. You'll probably need some paint thinners. Watch out for the chilling effect of thinners. It may crack the glass. The original Preen the great unstainer for spraying on shirt collars works quite well on wax. The newer Preen product is not so good.

For a wearing surface for the backpolish I used a sheet of glass with a thin felt layer glued down onto it with contact adhesive. There are some yellow cleaning cloths made of a synthetic felt which work quite well for this. Out here they are called "Jif" cloths and are made by Unilever. You likely have this product in the UK.

The cerium oxide and water is a light slurry.

You have to stretch and fold the felt cloth over the edge of the glass and glue down onto the back as well otherwise it wrinkles and patchworks your polish.

You do this in two stages, gluetacking the felt cloth onto the face of the glass, stretching it reasonably tight. Let it set. Second stage - firmly glueing the overhang of the felt around and onto the back of the glass. I found that an overhang of about 10mm was enough.

For glueing the overhang onto the back of the glass, you use the conventional method of coating of both surfaces with the glue and allowing the glue to dry off before applying both surfaces to each other. Pull and wrap so that there is some stretch applied to the felt so that it does not gather back onto the front in wrinkles.

The glue coat on the wearing face of the glass has to be very thin and evenly spread otherwise it will make hard high points in the felt. Do not put glue on the felt, just let it cling to the glue on the glass.

The glue coat on the back can be very generous like the normal method of using contact adhesive. Make sure the glue gets good penetration into the felt on the back surface but that no hard hight point seeps around to the front surface.

I had trouble getting an even finish by hand around a CD-R sized disk and made a machine to do the job. You will likely have much better luck handfinishing the smaller SG disk.

Wear gloves when using any of this grinding and polishing stuff otherwise you may reap the whirlwind twentyfive years down the track.

Done right, you can achieve sharper apparent resolution. You may get some ghosting on highlights so keep your out-of-focus backgrounds darker. White bark on tree branches may ghost cruelly.The vision from this disk will intercut almost seamlessly with direct-to-camera vision.

Enjoy.

Last edited by Bob Hart; May 19th, 2009 at 08:18 AM. Reason: errors
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Old May 19th, 2009, 03:17 AM   #3
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Hi Bob

Ta mate for the thorough lengthy advice.I think I have followed your posts on wax screens - not sure if it was you.Been there done that and can't get rid of the DIY bug.Oh to get that last ounce of resolution.Will keep at it for sure and post results as and when.Again - thanks for the advice.
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Old May 19th, 2009, 08:03 AM   #4
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I did a bit of testing with wax with mixed blessings. Best image but bad flicker due to variable density due to thickness changes in the layer. I figured my own disks and they were never absolutely true. They also warped when creeping the wax layer in as they were only 0.9mm thick.

These were CD-R sized disks (5" diam). The smaller SGPro disks may be viable for wax composite disks. A wax composite (wax betrween two glass sheets is a mongrel to keep centric, balance right and is heavier. I also tried fruit wax as a single sprayed on layer but it was not successful.

The names Oscar Spier and Jim Lafferty come to mind relating to wax experiments. JIm was also doing some interesting stuff with a synthetic. I don't know where this work ended up, successful or dead-end. Jim, if you are there maybe an update if there was a successful outcome. There were other names, however short of trolling back through posts on a slow internet I cannot otherwise recall them.

Here are some links to some stills of wax tests I did, shot with a PD150. The wax layer was a bit thin and there is some aerial image ghosting. They tested to the resolution limit of the PD150 with a chart at 530 lines. The wax blend was about 15% beeswax in parrafin wax. If you search "bienenwachs" and "Movietube" on this site you may find the relvent archived posts.

Temp footnote. Can't get to the links. Got a 403 forbidden error message. May have to log in again. Look up www.dvinfo.net/media/hart

If you can get in, the waxdisk tests should be on the bottom of the file list.

Furthur footnote. Got the forbidden message again, so I cannot help you with the lists.

There is another old archive www.dvinfo.net/media/mellor which might be worth a look.

Last edited by Bob Hart; May 19th, 2009 at 08:22 AM. Reason: added text
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Old May 19th, 2009, 04:34 PM   #5
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Ta mate

Those links seem to be archived or something.Anyway - the SGblade made me forget about the wax screens.What are you doing now?Still experimenting or moved on completely.To be fair I cannot wait till the day when I can just pull out a DSLR type camcorder that will rid me of these bulky DOF adaptors.
My rant at this time is that I do suspect that the major players are all colluding to hold the tech back.Every DSLR that shoots video is, it seems, purposley deficient in a key area and not because of a lcak of know how.Codec, frame rate,no HD output etc.Guess time will force their hand and of course RED.
I cry sometimes when I see what is being produced with the 5D and imagine what it could be.I had placed my order but cancelled because of the deliberate crippling - oh well.Hopefully in time we can get what we need....rant over...have a nice day Bob and will follow your posts closely.
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Old May 20th, 2009, 10:02 AM   #6
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No more R&D on my own adaptor. - I progressed it as much as I could with the tech I have. The Letus, SGPro/Blade, Cinevate and Redrock can all do better these days. I could improve it by a furthur redesign and new prisms but there is little point except for being able to do fast shutter speeds.

My current obsession is getting a pre-prod promotional trailer made and waiting for the EX3 relays from Letus to multiply and get turned loose all fattened up to market.

I have modified an Extreme for centricity and a wider groundglass view for the SI2K. It works sort of okay with the Voigtlander for Nikon 40mm or Nikon 45mm primes as relay but I think may work a whole lot better with the EX3 relay which will be sharper for its focal length.

Deliberately crippled? Maybe, maybe not. There is a lot of compromise in trying to wring the absolute most out of of what is essentially a half-decent home computer shoehorned into a DSLR body. There is also the Jack of All Trades thing where one combined product will never do all jobs equally well.

My imagining is that Canon and Nikon may well be playing it careful not to push motion video manufacturers to go all predatory in their stills marketplace. Having RED roll around across both sectors is a bit of a wild card for them - how to cover the bases and yet not provoke the motion video specialists and vice versa.

Unfettered competition in business can be a good thing but there is also a point where it goes a little awry and can become a barely affordable luxury. There has to be a long enough production run of any one item for economies of scale to kick in.

For all things to be sustainable there needs to be a balance. Maintaining that balance in a fair and just way is the challenge.

Those of us who were messing with groundglass adaptors made our own predictions on the extinction of our endeavours by the 35mm sensors when they came along. Perhaps there is a little sentimental regret. What is for sure is that in the way of movies, a lot of dross is going to get made and be harder for people to sift through for the gems because much of it will look so good because of the new tech which is upon us.
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Old May 20th, 2009, 06:22 PM   #7
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Quote
'What is for sure is that in the way of movies, a lot of dross is going to get made and be harder for people to sift through for the gems because much of it will look so good because of the new tech which is upon us.'


True words Bob.
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