Ground Glass Woes at DVinfo.net

Riley Stearns · August 6th, 2005, 09:23 PM

I'm trying to gather which of the ground glass/focus screens would be the best option for a static adapter that uses 55mm filter rings. I don't mind having to file down the screen to fit the ring or paying a little extra for better quality. I've been hearing about diffusion problems with the optosigma, but of the screen shots I've seen it looks good enough. Any suggestions would be great. Thank you very much.

Ben Winter · August 7th, 2005, 05:01 PM

This is how I understand it:

Optosigma ground glass: Has issues with letting in too much undiffused light, causing DOF to be lessened. Visible grain but not too bad.

Thorlabs ground glass: Has imperfections and swirling, bad choice.

Microcrystalline wax: Difficult to get a good thin layer of it for use as a diffuser, and it's not reliable. Bubbles and deformations appear in 100 F heat. Many people use it and can still see visible grain.

Paraffin wax: Visible grain, however I've heard success stories with it.

Beattie/Whatever other company makes em focusing screens: These are the screens that go in SLR cameras right before the viewfinder that you look at the image through. It's hard to find one without markings (grids, crosshairs, etc.) but if you do find one, they'res one good choice: The Nikon Red Dot "D" screen. Has no markings and very good light transmittance. It's used by astrophotographers for capturing stars at night, so it has to be decent. "Marla" (www.marlathemovie.com) was apparently filmed this way. I'm trying it myself, I'll let you know how that rolls.

Spinning diffused packaging CD: Spins the fogged up plastic CD that comes packaged with the Memorex? 25-pack. Results appear to be grainless, but you're losing a few f-stops and cmon...do you really want to trust your precious optical image with a piece of packaging plastic?

If I'm missing anything please someone add to this.

Oscar Spierenburg · August 7th, 2005, 05:30 PM

I'd like to correct some confusion about the micro-wax. It's probably the only way to get a static GG with no grain. You can only see a static pattern on smaller apertures. It's most likely that the G35 has a wax screen but certainly the MovieTube. You loose just a little light (1 or 2 F stops)
I made two perfect microwax screens, it's not easy, but not too difficult. It proved to be very reliable with shocks, traveling and high temperatures. I do not recommend anyone to try and make one unless you enjoy messing around with these things. If someone missed it, I made a fairly easy guide on my site on how to make a microwax screen.

Riley Stearns · August 7th, 2005, 07:09 PM

I like the idea of using the Nikon Type D, but it appears to be too small to mount in a 55mm filter ring. Is that correct?

The wax seemed like a complicated proccess back when I started building mine, but now that I've completed my basic adapter it might be worth looking into again.

Ben Winter · August 7th, 2005, 11:32 PM

It is too small. However, I've successfully practiced mounting a focusing screen into my adapter my simply taping it in there with a piece of mailing tape--doing that, I've had to zoom in very little to fill the frame with it. So, what you could do is ake a 55mm UV Filter (we use those things here like scraps of paper lol) and glue it to the filter using four tiny daubs of superglue the size of a pinhead (the amount of glue used can be extremely small and around the edges which don't show up anyway). Then you can mount the focus screen like you would any other 52mm filter. Basically, there's a lot of ways to go about mounting it and I'm sure you could find one that works for you.

I'd also like to remind everyone that reading a tutorial always makes the process seem harder than it really is.

Bill Porter · August 8th, 2005, 03:08 AM

I would like to point out that focusing screens come in much more than SLR cameras. They also come in medium format, large format, and other cameras as well, in corresponding sizes.

Also before you decide a focusing screen is too small, check out the size of the image on your screen/GG that you are actually filming.

Ben Winter · August 8th, 2005, 11:25 AM

I meant that it's too small to mount in a 55mm ring. In terms of the projected image, it's the perfect size.

August 6th, 2005, 09:23 PM	#1
Riley Stearns Regular Crew Join Date: Jan 2005 Location: Austin, TX Posts: 94	Ground Glass Woes I'm trying to gather which of the ground glass/focus screens would be the best option for a static adapter that uses 55mm filter rings. I don't mind having to file down the screen to fit the ring or paying a little extra for better quality. I've been hearing about diffusion problems with the optosigma, but of the screen shots I've seen it looks good enough. Any suggestions would be great. Thank you very much. __________________ i can't yet see Productions

August 7th, 2005, 07:09 PM	#4
Riley Stearns Regular Crew Join Date: Jan 2005 Location: Austin, TX Posts: 94	I like the idea of using the Nikon Type D, but it appears to be too small to mount in a 55mm filter ring. Is that correct? The wax seemed like a complicated proccess back when I started building mine, but now that I've completed my basic adapter it might be worth looking into again. __________________ i can't yet see Productions

August 7th, 2005, 05:01 PM	#2
Ben Winter Trustee Join Date: Jun 2005 Location: Hollywood, CA Posts: 1,675 Images: 1	This is how I understand it: Optosigma ground glass: Has issues with letting in too much undiffused light, causing DOF to be lessened. Visible grain but not too bad. Thorlabs ground glass: Has imperfections and swirling, bad choice. Microcrystalline wax: Difficult to get a good thin layer of it for use as a diffuser, and it's not reliable. Bubbles and deformations appear in 100 F heat. Many people use it and can still see visible grain. Paraffin wax: Visible grain, however I've heard success stories with it. Beattie/Whatever other company makes em focusing screens: These are the screens that go in SLR cameras right before the viewfinder that you look at the image through. It's hard to find one without markings (grids, crosshairs, etc.) but if you do find one, they'res one good choice: The Nikon Red Dot "D" screen. Has no markings and very good light transmittance. It's used by astrophotographers for capturing stars at night, so it has to be decent. "Marla" (www.marlathemovie.com) was apparently filmed this way. I'm trying it myself, I'll let you know how that rolls. Spinning diffused packaging CD: Spins the fogged up plastic CD that comes packaged with the Memorex? 25-pack. Results appear to be grainless, but you're losing a few f-stops and cmon...do you really want to trust your precious optical image with a piece of packaging plastic? If I'm missing anything please someone add to this.

August 7th, 2005, 05:30 PM	#3
Oscar Spierenburg Major Player Join Date: Jan 2005 Location: (The Netherlands - Belgium) Posts: 735	I'd like to correct some confusion about the micro-wax. It's probably the only way to get a static GG with no grain. You can only see a static pattern on smaller apertures. It's most likely that the G35 has a wax screen but certainly the MovieTube. You loose just a little light (1 or 2 F stops) I made two perfect microwax screens, it's not easy, but not too difficult. It proved to be very reliable with shocks, traveling and high temperatures. I do not recommend anyone to try and make one unless you enjoy messing around with these things. If someone missed it, I made a fairly easy guide on my site on how to make a microwax screen.

August 7th, 2005, 11:32 PM	#5
Ben Winter Trustee Join Date: Jun 2005 Location: Hollywood, CA Posts: 1,675 Images: 1	It is too small. However, I've successfully practiced mounting a focusing screen into my adapter my simply taping it in there with a piece of mailing tape--doing that, I've had to zoom in very little to fill the frame with it. So, what you could do is ake a 55mm UV Filter (we use those things here like scraps of paper lol) and glue it to the filter using four tiny daubs of superglue the size of a pinhead (the amount of glue used can be extremely small and around the edges which don't show up anyway). Then you can mount the focus screen like you would any other 52mm filter. Basically, there's a lot of ways to go about mounting it and I'm sure you could find one that works for you. I'd also like to remind everyone that reading a tutorial always makes the process seem harder than it really is.

August 8th, 2005, 03:08 AM	#6
Bill Porter Major Player Join Date: Mar 2005 Location: Ventura, California, USA Posts: 751	I would like to point out that focusing screens come in much more than SLR cameras. They also come in medium format, large format, and other cameras as well, in corresponding sizes. Also before you decide a focusing screen is too small, check out the size of the image on your screen/GG that you are actually filming.

August 8th, 2005, 11:25 AM	#7
Ben Winter Trustee Join Date: Jun 2005 Location: Hollywood, CA Posts: 1,675 Images: 1	I meant that it's too small to mount in a 55mm ring. In terms of the projected image, it's the perfect size.