Condensers wow!

Donnie Wagner · July 28th, 2005, 02:47 PM

Oscar,
Has you (or someone on this forum) tried arranging lenses the same as shown in the movietube patent, minus the prism?

e.g. 35mm-(|) () (()

Donnie Wagner · July 28th, 2005, 02:57 PM

oops, clicked submit...

so anyway, with this
35mm (|) () (()
I was trying to show lenses in this order...
35mm, pcx, gg, pcx, field lens, achromat

That is what the movietube shows. Anyone tried it?

This site shows why a field lens is used in optical tube-like systems, it seems to be able to fix the hotspot, but i dont know optics well enough to translate this info into our adapter design.
http://www-optics.unine.ch/education...ield_lens.html

Also, according to this page we should be doing this )|(
http://www-optics.unine.ch/education...berration.html

Leo Mandy · July 28th, 2005, 05:09 PM

Interestingly enough, the second picture with the right and wrong way shows that after the light has hit the PCX lens from the flat side, it would come out flat on the other, which is untrue and I can attest for that with the distortion and blurriness I am getting with a condenser. So what is the deal?

Glen Hurd · July 29th, 2005, 01:10 AM

Quote:

Originally Posted by Donnie Wagner

oops, clicked submit...

Also, according to this page we should be doing this )|(
http://www-optics.unine.ch/education...berration.html

Actually, the second example there represents the hot-spot scenario. Light from the ground glass is scattering off the glass in many directions, being most intense where it lines up with your eye (or video lens).

We don't see such hot-spots in film because every crystal on film receives the same amount of light proportional to the scene. The film is a "slice" across the focal plane, getting an accurate representation of the photographed scene's lighting. But we aren't working with slices. We're dealing with projectors.

In the adaptor scenario, the gg is a projector, and creates the hot-spot problem. To act as a projector, it must diffuse light (heavily). This diffusion/scattering causes light to be "lost" as it gets further away from the center of the picture -- your eye never gets to see it since it bounces off in some wild direction. Apparently, the second PCX (PCX2, between gg and video) works by getting that scattered light to refocus along the lens axis to the video camera -- bringing the "lost" light back into the path of the lens, and thus brightening what was once dark.

So, the second example in the link you posted represents a situation where the PCX is trying to refocus the scattered light into a parallel stream, in effect, removing the hot spot.

The first PCX (PCX1, located between 35mm lens and gg) is probably more purposed to reverse any distortion caused by PCX2, since the light entering it has already been focused onto the ground glass at a pretty extreme angle and probably doesn't have any "hotspot" issues in this section of the pipeline. I haven't been able to experiment with it, however.

So I would interpret your link as supporting the (|) configuration that others have been finding to be successful.

Sorry for being so verbose. I can't help it.

Leo Mandy · July 29th, 2005, 06:51 AM

I am also curious about the first PCX in this way - when I have tried it, it makes the image smaller - is this what it is supposed to do? Or is it more a fact that it concentrates the light into one spot instead of the graduated light spread you regularly get from a lens onto a GG?

Glen Hurd · July 29th, 2005, 04:05 PM

My guess is that the first PCX is compensating the second.
One thing that bothered me about the second PCX is that it enlarges the image, and I thought it was simply getting rid of the hot spot by enlarging the bright portion of the screen and ignoring the darker areas. Do this too much, and you completely lose any reason for using an adapter at all (remember, you can get shallow DOF in video just by using a real long lens, or "magnifying" the image).
Now I realize the second PCX is actually redirecting the light back toward the lens, correcting a problem created by the diffusion of the ground glass.
With the second PCX close to the GG, there's not going to be a lot of magnification, but by having the first PCX on the other side, it seems that it would "reverse" or reduce whatever magnification/distortion was created by the second PCX.
Again, I don't have a rig set up to carefully experiment with these ideas, but "thought experiments" can help.

Donnie Wagner · August 2nd, 2005, 06:55 PM

FYI,
I tried this setup and it has given me the best results yet, no noticable hot-spot and no distortion or blurring towards the edges. Also, I set a two tripods up, one with a still camera, and the other with my vx2000 and the lens adapter. I tried my 50mm lens on both to make sure I was getting the same frame and angle of view. "a" OK!

camcorder ) (| 35mm lens

I was concened about putting one of the pcx lenses between the 35mm lens and the GG, so I tried this and it works great for my setup. the two pcx lenses are fl 150mm. And I put as much space between them as I could. Hope to post pics soon.

Leo Mandy · August 2nd, 2005, 08:50 PM

It will be interesting to see what the PCX lens will do for quality of the image. Did you get them at Surplusshed?

July 28th, 2005, 02:47 PM	#16
Donnie Wagner Regular Crew Join Date: Dec 2004 Location: Pittsburgh, PA Posts: 135	Oscar, Has you (or someone on this forum) tried arranging lenses the same as shown in the movietube patent, minus the prism? e.g. 35mm-(\|) () (()

July 28th, 2005, 02:57 PM	#17
Donnie Wagner Regular Crew Join Date: Dec 2004 Location: Pittsburgh, PA Posts: 135	oops, clicked submit... so anyway, with this 35mm (\|) () (() I was trying to show lenses in this order... 35mm, pcx, gg, pcx, field lens, achromat That is what the movietube shows. Anyone tried it? This site shows why a field lens is used in optical tube-like systems, it seems to be able to fix the hotspot, but i dont know optics well enough to translate this info into our adapter design. http://www-optics.unine.ch/education...ield_lens.html Also, according to this page we should be doing this )\|( http://www-optics.unine.ch/education...berration.html

July 28th, 2005, 05:09 PM	#18
Leo Mandy Major Player Join Date: Dec 2004 Posts: 749	Interestingly enough, the second picture with the right and wrong way shows that after the light has hit the PCX lens from the flat side, it would come out flat on the other, which is untrue and I can attest for that with the distortion and blurriness I am getting with a condenser. So what is the deal?

July 29th, 2005, 06:51 AM	#20
Leo Mandy Major Player Join Date: Dec 2004 Posts: 749	I am also curious about the first PCX in this way - when I have tried it, it makes the image smaller - is this what it is supposed to do? Or is it more a fact that it concentrates the light into one spot instead of the graduated light spread you regularly get from a lens onto a GG?

July 29th, 2005, 04:05 PM	#21
Glen Hurd Regular Crew Join Date: Jul 2005 Location: Burlington, NJ Posts: 59	My guess is that the first PCX is compensating the second. One thing that bothered me about the second PCX is that it enlarges the image, and I thought it was simply getting rid of the hot spot by enlarging the bright portion of the screen and ignoring the darker areas. Do this too much, and you completely lose any reason for using an adapter at all (remember, you can get shallow DOF in video just by using a real long lens, or "magnifying" the image). Now I realize the second PCX is actually redirecting the light back toward the lens, correcting a problem created by the diffusion of the ground glass. With the second PCX close to the GG, there's not going to be a lot of magnification, but by having the first PCX on the other side, it seems that it would "reverse" or reduce whatever magnification/distortion was created by the second PCX. Again, I don't have a rig set up to carefully experiment with these ideas, but "thought experiments" can help.

August 2nd, 2005, 06:55 PM	#22
Donnie Wagner Regular Crew Join Date: Dec 2004 Location: Pittsburgh, PA Posts: 135	FYI, I tried this setup and it has given me the best results yet, no noticable hot-spot and no distortion or blurring towards the edges. Also, I set a two tripods up, one with a still camera, and the other with my vx2000 and the lens adapter. I tried my 50mm lens on both to make sure I was getting the same frame and angle of view. "a" OK! camcorder ) (\| 35mm lens I was concened about putting one of the pcx lenses between the 35mm lens and the GG, so I tried this and it works great for my setup. the two pcx lenses are fl 150mm. And I put as much space between them as I could. Hope to post pics soon.

August 2nd, 2005, 08:50 PM	#23
Leo Mandy Major Player Join Date: Dec 2004 Posts: 749	It will be interesting to see what the PCX lens will do for quality of the image. Did you get them at Surplusshed?