New moving ground glass mechanism

Aaron Shaw · January 1st, 2005, 06:34 PM

Thanks Brett. I have looked at Edmund Optics, the Surplus Shed, and Opto Sigma but the largest I can usually find is 50mm in diameter. I would like to get 60mm at least. For instance, Opto-Sigma only makes a 50mm GG. :(

Steven Fokkinga · January 11th, 2005, 03:48 PM

Hi Dan,

Are you progressing on the adapter? When do you expect to have a testable prototype? Also do you have in the meantime some high(er) quality footage??

Keep the good work up!

Steven

Dan Diaconu · January 11th, 2005, 04:25 PM

Thanks Steven,

I have to wear a few hats (at the same time) in this process, which made me bang the walls, but it's refreshing.........whoa!

I allready have tested the prototypes I made, but I have improved the design. I can drop it on concrete now, pick it up and shoot (if the lens is still there....lol)
Not that I recomend it!!!!

I have seen too many times what an "early release" can do to a lot of work. I can not AFFORD THAT.

I will keep my promise to deliver what I promised.

Daniel Stone · January 17th, 2005, 12:54 AM

Anyone ever used a BosScreen? I hear it's a completely grain-free ground glass with excellent picture contrast. If this is so, it may be an excellent choice for a non-oscilating ground glass unit.

I'm thinking about ordering a sheet just for test-purposes unless someone on here has used it before.

Here's the link:

http://www.stabitech.nl/Bosscreen.htm#top

Régine Weinberg · January 17th, 2005, 12:59 AM

G'day, I do know that link and the only con ---it melts if it is hot
and or direct sunlight --after the sreen is gone to be useless.

Daniel Stone · January 17th, 2005, 01:15 AM

Yea, I saw that - kinda sucks ... but if it's really as good as I've read, it'd be totally worth it to me to treat it with 'special' care.

I've sent them an email to get pricing on a smaller sheet without grid lines. We'll see.

Frank Ladner · January 17th, 2005, 09:36 AM

I've been experimenting with microcrystalline wax and it is definately better (in terms of grain (( none visible )) and sharpness) than any ground glass I've tested. I think it is the best static solution. I've yet to have any wax melt, but I have taken a hairdryer and intentionally melted the wax that was sealed between glass (couldn't escape) to see the effects. After it cooled it was right back to normal. I'm not sure if there would be any discoloration due to reheating over the long term, but I don't think it would be a big problem.

Given the quality of Microcrystalline wax (if you get the right thickness w/o bubbles), I think it would be easier to go through the trouble of building some kind of small cooling system than to build rotating / oscillating glass solutions. (Taking into consideration the precision required with the non-static adapters.)

Jim Lafferty · January 17th, 2005, 09:38 AM

There's no reason to expect a Boss Screen or any other microwax screen to "melt" provided you keep your camera away from blisteringly hot circumstances -- which you do normally, right? An example of how you could melt such a screen would be to leave your camera and adapter in the trunk of your car on an exceptionally hot day for hours at a time.

Dan Diaconu · January 17th, 2005, 10:38 AM

Frank,
Would it possible for us to see a 4 sec clip showing something sharp ECU (about 1/3 of the frame) while barely panning? It would be nice to see how clean the BG looks like when soft. Or even easier: 1.4 (or otherwise wide open ) 50-85-135mm lens, night shot, city lights, focus at the closest setting of the lens. Sloooow pan. It should look nice.

Frank Ladner · January 17th, 2005, 11:17 AM

Dan: I will definately try and capture some closeup, barely-panning footage. I won't be able to do the "city lights" thing for ya, though as I live out in the woods. LOL!

Here's some of the footage / framegrabs I have available now, in case you haven't seen them:
http://209.214.235.122/mwtest/

Dan Diaconu · January 17th, 2005, 01:12 PM

Frank,

I saw the pics and first clip (slooow download to go for the other two but I will watch them) so will only comment on what I have seen so far:

The "look" is definitely there. You've got it and is BEAUTIFULL. Bravo!!!

Sharpness? Is subject to precise focusing (on the SLR lens AND the camcorder lens on the screen)
That is why I suggested a sloooow pan with a CU (precise focused) but since there is too much about focus (and focusing techniques while in motion) a static still is best to demonstrate the apparatus.

So far, the pics seems a touch soft (overall) It may be that the lens was not focused on the GG at best, or.... the thickness of the wax was too big. I have not experimented the wax technic but I can only imagine that if it is too thick, focus will not happen on a plane, but in the thickness of the wax layer (hence soft) you know better what can be done.
However it is amazing (to me) how well and even you managed to spread it.
One "sin" is still there though.
Vigneting. Not your fault (of course).
Here is a thought to overcome it:
Take a "normal focusing screen" from your SLR and wax the matte side. You will get rid of any AF marks or anything may be there and get the best of a static GG that can be made. The Fresnel (from the other side) will help you with vigneting while having the mattest matte surface to focus on, on the opposite side, and you are in business.
I will not try it since I have experienced a great loss of screens trying to "matte" the matte side with acetone, milling them, clear nail lacquer, etc while keeping CLEAN the Fresnel side!!!!. Did not get them to a satisfactory surface. Maybe wax is the solution. I'll be curious if you can get acceptable results. I will define what I see as acceptable: If you can take a still (high rez) and footage (nothing fancy, nothing moving too much, a slow pan at most or just a slow focus roll between MARKED distances!)and display it on a 50" plasma (in a local electronics retailer) and you like the image, than is not acceptable, is very good. You may be your best critic.
I hope this helps.

PS1
Try a 4, 5.6, 8 as well to find out limitations (if any...)
PS2 Saw the second clip. All of the above still valid.

Frank Ladner · January 17th, 2005, 02:42 PM

Dan,

Thanks for checking out some of the footage! Thank you for the compliment!

You are absolutely right about the wax layer. If it is too thick, the image/light gets distributed throughout and becomes too soft. I am not working with the most precise measurements. - I would have to express the distance in terms of how many times the aluminum strips are folded. :-)

As far as the vignetting - I recently got some condensers in and have yet to shoot some new footage with them. They clearly make a difference when I look at the projected image, holding the pieces together by hand, but how the camera will see it is yet to be determined.

I have wondered if waxing a ground glass would work. I know it would help lessen the grain, but I dismissed the idea thinking that I might as well just go for all-wax to get the best possible image. HOWEVER, given the fact that the ground side of the glass is diffuse the wax should distribute more evenly, catching the wax in the 'pits' where the glass has been ground. I think gravity would do the work here. As long as you have an even grind, you should get an even layer of wax.

Once it cools, you would still need a glass covering for the wax layer.

Hrm...sounds like something worth a try.

Thank you for all the feedback and advice!

Brett Erskine · January 17th, 2005, 03:33 PM

Frank great job on he wex technique. I did notice something else that hasnt been mentioned though. It appears that the image becomes increasingly more out of focus near the edges of the screen. I've seen this happen in some of my tests as well. The problem and solution is this:

The problems is your video camera's lens is too close to the wax screen. When ever a video camera films something flat thats extremely close the video camera lens it can not keep the entire object in focus at one time. The reason being is that the distance between the center of the wax screen (or object) and the cameras CCD vs. the distance between the outter edges of the screen (object) and the CCD is slightly different. Its extremely minor but at these very short distances every mm counts when it comes to DOF.

The solution is simple. Simply increase the distance between the wax screen and the camera's CCDs. A few inches should do. This also fixes another problem that you may or may not have noticed - barrel distortion. At these extremely close distances on wider lenses your going to get some. Moving the screen away a few inches and zooming in a tad to reframe will fix this.

To test both of these problems simply shoot a piece of graph paper and make sure the lines stay in focus and perfectly square.

Frank Ladner · January 17th, 2005, 08:59 PM

You are right about the edges being out of focus. I just assumed a condenser could fix it, but what you are saying makes perfect sense. I will mount the glass further away from the camera and zoom in a bit more. This, combined with condensers, should give a pretty nice image.

Thanks for the info, Brett!

Kyle Cutshaw · January 18th, 2005, 12:09 PM

Frank- Can you tell us how you made your wax diffuser? Sounds like a good alternative to gg.

January 18th, 2005, 12:09 PM	#105
Kyle Cutshaw New Boot Join Date: Jan 2005 Location: seymour, tennessee Posts: 21	wax diffuser Frank- Can you tell us how you made your wax diffuser? Sounds like a good alternative to gg. __________________ "Nothing takes the taste out of peanut butter quite like unreqited love." -Charlie Brown

January 1st, 2005, 06:34 PM	#91
Aaron Shaw Major Player Join Date: Jul 2004 Posts: 587	Thanks Brett. I have looked at Edmund Optics, the Surplus Shed, and Opto Sigma but the largest I can usually find is 50mm in diameter. I would like to get 60mm at least. For instance, Opto-Sigma only makes a 50mm GG. :(

January 11th, 2005, 03:48 PM	#92
Steven Fokkinga Major Player Join Date: May 2004 Location: The Netherlands Posts: 204	Hi Dan, Are you progressing on the adapter? When do you expect to have a testable prototype? Also do you have in the meantime some high(er) quality footage?? Keep the good work up! Steven

January 11th, 2005, 04:25 PM	#93
Dan Diaconu Major Player Join Date: Dec 2004 Location: Vancouver, Canada Posts: 804	Thanks Steven, I have to wear a few hats (at the same time) in this process, which made me bang the walls, but it's refreshing.........whoa! I allready have tested the prototypes I made, but I have improved the design. I can drop it on concrete now, pick it up and shoot (if the lens is still there....lol) Not that I recomend it!!!! I have seen too many times what an "early release" can do to a lot of work. I can not AFFORD THAT. I will keep my promise to deliver what I promised.

January 17th, 2005, 12:54 AM	#94
Daniel Stone Regular Crew Join Date: Jun 2004 Location: Washington, DC Posts: 84	Anyone ever used a BosScreen? I hear it's a completely grain-free ground glass with excellent picture contrast. If this is so, it may be an excellent choice for a non-oscilating ground glass unit. I'm thinking about ordering a sheet just for test-purposes unless someone on here has used it before. Here's the link: http://www.stabitech.nl/Bosscreen.htm#top

January 17th, 2005, 12:59 AM	#95
Régine Weinberg Major Player Join Date: Jan 2004 Location: Bordeaux, going to Bangkok, 2011 Posts: 232	G'day, I do know that link and the only con ---it melts if it is hot and or direct sunlight --after the sreen is gone to be useless.

January 17th, 2005, 01:15 AM	#96
Daniel Stone Regular Crew Join Date: Jun 2004 Location: Washington, DC Posts: 84	Yea, I saw that - kinda sucks ... but if it's really as good as I've read, it'd be totally worth it to me to treat it with 'special' care. I've sent them an email to get pricing on a smaller sheet without grid lines. We'll see.

January 17th, 2005, 09:36 AM	#97
Frank Ladner Major Player Join Date: Aug 2003 Location: Poplarville, MS Posts: 453	I've been experimenting with microcrystalline wax and it is definately better (in terms of grain (( none visible )) and sharpness) than any ground glass I've tested. I think it is the best static solution. I've yet to have any wax melt, but I have taken a hairdryer and intentionally melted the wax that was sealed between glass (couldn't escape) to see the effects. After it cooled it was right back to normal. I'm not sure if there would be any discoloration due to reheating over the long term, but I don't think it would be a big problem. Given the quality of Microcrystalline wax (if you get the right thickness w/o bubbles), I think it would be easier to go through the trouble of building some kind of small cooling system than to build rotating / oscillating glass solutions. (Taking into consideration the precision required with the non-static adapters.)

January 17th, 2005, 09:38 AM	#98
Jim Lafferty Major Player Join Date: Dec 2003 Location: Brooklyn, NY Posts: 636	There's no reason to expect a Boss Screen or any other microwax screen to "melt" provided you keep your camera away from blisteringly hot circumstances -- which you do normally, right? An example of how you could melt such a screen would be to leave your camera and adapter in the trunk of your car on an exceptionally hot day for hours at a time.

January 17th, 2005, 10:38 AM	#99
Dan Diaconu Major Player Join Date: Dec 2004 Location: Vancouver, Canada Posts: 804	Frank, Would it possible for us to see a 4 sec clip showing something sharp ECU (about 1/3 of the frame) while barely panning? It would be nice to see how clean the BG looks like when soft. Or even easier: 1.4 (or otherwise wide open ) 50-85-135mm lens, night shot, city lights, focus at the closest setting of the lens. Sloooow pan. It should look nice.

January 17th, 2005, 11:17 AM	#100
Frank Ladner Major Player Join Date: Aug 2003 Location: Poplarville, MS Posts: 453	Dan: I will definately try and capture some closeup, barely-panning footage. I won't be able to do the "city lights" thing for ya, though as I live out in the woods. LOL! Here's some of the footage / framegrabs I have available now, in case you haven't seen them: http://209.214.235.122/mwtest/

January 17th, 2005, 01:12 PM	#101
Dan Diaconu Major Player Join Date: Dec 2004 Location: Vancouver, Canada Posts: 804	Frank, I saw the pics and first clip (slooow download to go for the other two but I will watch them) so will only comment on what I have seen so far: The "look" is definitely there. You've got it and is BEAUTIFULL. Bravo!!! Sharpness? Is subject to precise focusing (on the SLR lens AND the camcorder lens on the screen) That is why I suggested a sloooow pan with a CU (precise focused) but since there is too much about focus (and focusing techniques while in motion) a static still is best to demonstrate the apparatus. So far, the pics seems a touch soft (overall) It may be that the lens was not focused on the GG at best, or.... the thickness of the wax was too big. I have not experimented the wax technic but I can only imagine that if it is too thick, focus will not happen on a plane, but in the thickness of the wax layer (hence soft) you know better what can be done. However it is amazing (to me) how well and even you managed to spread it. One "sin" is still there though. Vigneting. Not your fault (of course). Here is a thought to overcome it: Take a "normal focusing screen" from your SLR and wax the matte side. You will get rid of any AF marks or anything may be there and get the best of a static GG that can be made. The Fresnel (from the other side) will help you with vigneting while having the mattest matte surface to focus on, on the opposite side, and you are in business. I will not try it since I have experienced a great loss of screens trying to "matte" the matte side with acetone, milling them, clear nail lacquer, etc while keeping CLEAN the Fresnel side!!!!. Did not get them to a satisfactory surface. Maybe wax is the solution. I'll be curious if you can get acceptable results. I will define what I see as acceptable: If you can take a still (high rez) and footage (nothing fancy, nothing moving too much, a slow pan at most or just a slow focus roll between MARKED distances!)and display it on a 50" plasma (in a local electronics retailer) and you like the image, than is not acceptable, is very good. You may be your best critic. I hope this helps. PS1 Try a 4, 5.6, 8 as well to find out limitations (if any...) PS2 Saw the second clip. All of the above still valid.

January 17th, 2005, 02:42 PM	#102
Frank Ladner Major Player Join Date: Aug 2003 Location: Poplarville, MS Posts: 453	Dan, Thanks for checking out some of the footage! Thank you for the compliment! You are absolutely right about the wax layer. If it is too thick, the image/light gets distributed throughout and becomes too soft. I am not working with the most precise measurements. - I would have to express the distance in terms of how many times the aluminum strips are folded. :-) As far as the vignetting - I recently got some condensers in and have yet to shoot some new footage with them. They clearly make a difference when I look at the projected image, holding the pieces together by hand, but how the camera will see it is yet to be determined. I have wondered if waxing a ground glass would work. I know it would help lessen the grain, but I dismissed the idea thinking that I might as well just go for all-wax to get the best possible image. HOWEVER, given the fact that the ground side of the glass is diffuse the wax should distribute more evenly, catching the wax in the 'pits' where the glass has been ground. I think gravity would do the work here. As long as you have an even grind, you should get an even layer of wax. Once it cools, you would still need a glass covering for the wax layer. Hrm...sounds like something worth a try. Thank you for all the feedback and advice!

January 17th, 2005, 03:33 PM	#103
Brett Erskine Major Player Join Date: Dec 2003 Location: Anaheim, CA Posts: 445	Frank great job on he wex technique. I did notice something else that hasnt been mentioned though. It appears that the image becomes increasingly more out of focus near the edges of the screen. I've seen this happen in some of my tests as well. The problem and solution is this: The problems is your video camera's lens is too close to the wax screen. When ever a video camera films something flat thats extremely close the video camera lens it can not keep the entire object in focus at one time. The reason being is that the distance between the center of the wax screen (or object) and the cameras CCD vs. the distance between the outter edges of the screen (object) and the CCD is slightly different. Its extremely minor but at these very short distances every mm counts when it comes to DOF. The solution is simple. Simply increase the distance between the wax screen and the camera's CCDs. A few inches should do. This also fixes another problem that you may or may not have noticed - barrel distortion. At these extremely close distances on wider lenses your going to get some. Moving the screen away a few inches and zooming in a tad to reframe will fix this. To test both of these problems simply shoot a piece of graph paper and make sure the lines stay in focus and perfectly square.

January 17th, 2005, 08:59 PM	#104
Frank Ladner Major Player Join Date: Aug 2003 Location: Poplarville, MS Posts: 453	You are right about the edges being out of focus. I just assumed a condenser could fix it, but what you are saying makes perfect sense. I will mount the glass further away from the camera and zoom in a bit more. This, combined with condensers, should give a pretty nice image. Thanks for the info, Brett!