Low grain bokeh GG screen for vibrating holder.

[Dreamish]

I found a way of making a very good low grain GG with perfect bokeh for vibration holder. But it is not easy to make and quite troublesome too.

I found that EE-S screen is nearly perfect for adapter use. It is grainless, and for some miracle reasons it is almost 100% diffusive, high tech laser matte, and very very low light loss. However, it exhibit few problems.
1.)The fresnel field on the back of the matte screen completely screw up the image. It helps uniform illumination of the GG but it causes radial blur, which become obvious when used with fast lens. So we need to remove the fresnel pattern.
2.)The bokeh is weird. Even it has no aerial image pass through. But there are weird "star" pattern in those out of focus highlights.

And the hand grind GG from snodart is also nearly perfect for adapter use. Because he uses a Nikon F3 focusing screen for GG. Nikon's focusing screen come with seperate condenser screen, which is perfect because we can grind a GG with condenser already integrated. However, unless you use very coarse aluminium oxide. It is impossible to produce proper bokeh.

So, let's just stick 2 together. And it worked LOL. The light loss is acceptable in my opinion. I can shoot even with a Sony V1. So I think the light loss is reasonable. The EE-S screen is used as a projection screen to catch the image. And the "Snodart" screen is used to "filter" out the laser matte pattern. However if you can live with the weird pattern bokeh. You can just use the EE-S combine with a Nikon condernser screen for super low grain low light loss screen.

I used a 9 Micron Aluminium Oxide "Snodart" screen. And stick the matte sides of 2 screens together with epoxy glue(APPLY GLUE TO THE EDGE ONLY, NOT APPLY TO THE SCREEN SURFACE). That's it. The "Snodart" screen diffuses the weird pattern of EE-S screen. And the bokeh become organic and natural. And the grain is same as a 9 Micron screen, which is very little grain. I can use my vibrating adapter stop down to f16 and still see no noticable grain.

However, the most tricky task is to remove the EE-S freshnel field. Which is the shiny side, not the matte side. The shiny side has a fresnel pattern on it which screw things up.

To remove the field. First, you need superhuman patient. You will probably give up but I found that it works great :p And you need a lot of sand paper. From coarse to fine. And very very fine. Get the sand paper from model shop. From grade 200 to grade 2000.

http://cgi.ebay.com/Tamiya-SD-Luts-MSD-FINISHING-ABRASIVES-Sand-Paper-UF_W0QQitemZ120134626818QQihZ002QQcategoryZ84635QQ rdZ1QQssPageNameZWD1VQQ_trksidZp1638.m118.l1247QQc mdZViewItem

You need to first completely destroy the field with coarse sand paper. Make sure it is completely removed. Then sand it with finer sand paper. Step by step, from 200=>400=>600=>1000=>1200=>2000 etc....until the surface is very smooth like silk.
Then you need some model polishing compound.

http://cgi.ebay.com/TAMIYA-S-3-pcs-Polishing-Compound-Coarse-Fine-Finish_W0QQitemZ370041333103QQihZ024QQcategoryZ259 4QQtcZphotoQQssPageNameZWDVWQQrdZ1QQcmdZViewItem

Again, from coarse to fine. And take a lot of patient.
Rub it with these compound until it is 100% shiny.

It is tough, but I did it. The combined screen worked freaking good.
It is not a cheap way to make a DIY GG. So I would suggest you to try it only if you have surplus canon screen and nikon screen and u don't know what to do with it.

[leteeci]

HHmmhmh.. Interesting!!!

But isn't that screen a little bit too heavy for vibrating mechanism??

And how the hack you keep mate side clean when you sand the fresnel out, if the screen is so delicate??

Thanks,

david

[Dreamish]

Yes, it is a little bit heavy. So a little bit stronger vibrating motor is needed.
I use electrical tapes to mask the matte side. That would give it some protection during sanding process. And electric tapes usually won't leave marks on the focusing screen. I guess using RC models' masking tape would give better protection.
Anyway I'm still trying to figure out how to sand it so that surface is completely flat.
But after going throught all this trouble. I'm think if it is worthy to compromise so much things to get the bokeh quality.

[Car3o]

the reason for the EE-s screen has shitty bokeh is because the diffusion isn't enough. so you're really just putting more diffusion to the screen. really more trouble and money than it's worth. use the screen Snodart uses, which is a hand ground made glass and you're money. if you want, then use a condenser to that. maybe i'm missing something in your setup.

[Dreamish]

Snodart screen don't give enough diffusion even using 15 Micron Aluminium Oxide. And anything higher than 15 micron will show too much grain and chips.
So using "clean" EE-S combine micron glass are just right and the grain is fine enough for vibrating adapters. And it gives similar bokeh quality of sgpro r3(I have access to a SGPro r3 adapter and used it for a big project.). Not sure about lightloss.

[Car3o]

ahh, gotcha...i thought his was fine...guess not.
check into light shaping diffuser screens.
you can find them under any LCD screen. cell phones mainly. greatest bokeh you will find. minimal grain depending on type of light screen and and decent on light loss. again depends on the lsd screen. you can get a sample from www.poc.com for like $39.00. Attach it to your vibrating design and should have some great results. Another upside is it spreads light evenly. No vignetting what-so-ever. i use in all my vibrating setups. I'm tackling spinning now, and can't afford one of those big enough. unless i find an lcd monitor or lcd tv that's already broken. I'm not 100% positive, but I think that is what the brevis is using. Their CFL 1-3 is different angles. The lower the angle, the smaller amount of grain and less diffusion, crappy bokeh.

-rh

[Dreamish]

A picture worth more than anything.
Finally I got some grab of this EE-S without fresnel crossover Snodart screen.
They do lose more light. But since EE-S lose so little light and create so much diffusion with those laser matte thingy. The lightloss is acceptable i would say.
Notice the bokeh. You need a very coarse grain GG to reproduce this diffusion quality.
The sharpness is enough for HD video. I will post HD grab later when I got a time.

[Dreamish]

I'm interested in these screen. I have requested a sample from them twice but never got any reply. And I don't think they will be interested to deal with me since I'm living in Hong Kong. Which is pathetic :(