Water and oil anamorphic prisms

Aaron Shaw · March 19th, 2005, 04:06 PM

Oscar, yeah those extra prism pieces are there to help correct for color aberration. Might be something to try though I'm not sure it's worth the effort.

Setup looks nice. You might want to consider putting a normal spherical lens in front of the whole prism construction.

You're going to have to balance the compression ratio vs aberrations it looks like. What sort of compression are you getting from the setup with both at 30 degree angles?

Oscar Spierenburg · March 19th, 2005, 05:34 PM

Your right Aaron, this might be the balance you are talking about:
http://doublecam.250free.com/exact-angles.jpg (these are exact angles.)

I checked the aspect ratio of my homemade double camera thing (other tread) which is a bit more than 4:3. So the compression I get with these adjusted angles will be very close to 16:9 and the color aberration is very much reduced.

In the image you can see I meant 30° for the lenses themselves.
And Aaron, what would a normal spherical lens do? (by the way, thanks for your replies)

Aaron Shaw · March 19th, 2005, 08:20 PM

Ah! I understand what you mean now. 30 degree angled prisms.

Looks like a workable setup :). I'm definitely looking forward to seeing some more screen grabs and footage!

Generally, anamorphic cinema lenses house the prisms between lens elements of some sort. You can sort of see an image of a variable anamorhpic lens here (variable because it changes the orientation of the lenses with the turn of the knob):

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&category=4791&item=5756817409&rd=1&ssPageName=WDVW

You can't really see the glass but if you look carefully there is a spherical piece of glass under which the prisms are held. I don't know if you will need one or not. It would be an interesting to test run. The lens, I believe, helps focus the light into the prism. You can change the field of view by changing the spherical glass etc.

Oscar Spierenburg · March 20th, 2005, 06:47 AM

I see, so maybe if you get the right spherical lenses, the water prisms could be much smaller if they are only to stretch the image collected (if this is the right term)by the front spherical lens.
Maybe this means that you'd have to focus the lenses apart from the normal lens? In my (current) case that's not necessary.

I'm definitely going to test a lot the coming days and post the results.

EDIT:
Oh, one more thing, maybe someone knows. It seems the lenses compress the image a bit more to the sides. Maybe there is a way, or better, a plug-in for after effects to stretch it more to the sides. Or less in the middle of course.

Oscar Spierenburg · March 27th, 2005, 07:59 AM

I had to make the small (round) lens over again and made a new one with straight pieces of museum-glass.
To begin testing, I made a rail system to mount the whole thing on.
The first two pictures on my site show my (very big) setup:

http://doublecam.250free.com/

The whole thing has to be covered with something, of course. Maybe some sunshades (flags?) too.

Leo Mandy · March 27th, 2005, 08:24 AM

Oscar, what is the small silver thing that is hanging from the Lens? It looks like a silver pointer stick or something....

Oscar Spierenburg · March 27th, 2005, 08:48 AM

It's a (are, actually) bolt(s) attached to the rear lens to adjust the angle if needed.
In the top image, you can see another bolt in sleeve, this is to adjust the angle of the whole lens.
Maybe I'll 'tune' the angles (for color aberration) with the camera hooked up to a big monitor.

Oscar Spierenburg · March 27th, 2005, 06:31 PM

Here is a new test frame (anamorphic lens and double-cam):

http://doublecam.250free.com/anamorph6.jpg

I still have too much color aberration on the right side of the frame. It's very much visible (like a red blur)on the edge of the right can.
I hope I can get rid of this by adjusting the angle of the rear water lens.

Oscar Spierenburg · March 29th, 2005, 05:22 PM

Anamorphic people, I'd like you to check out my new test, because it's a compromise between the compression (16:9) and the color aberration. I've adjusted the angles of the lenses to the camera lens and came up with almost no color shifting (also meaning a slight blur all over)
But the aspect ratio is quite a bit less than 16:9.

Here's the frame grab:

http://doublecam.250free.com/beer.jpg

This is before I adjusted the lenses:

http://doublecam.250free.com/anamorph6.jpg

If the top link doesn't work, click on the first text on my site:
http://doublecam.250free.com/

Oscar Spierenburg · March 31st, 2005, 08:34 AM

http://doublecam.250free.com/kom.jpg

Aaron Shaw · March 31st, 2005, 07:11 PM

Those look surprisingly good :) ! Great work!

Any chance you could post a shot with and without the adapter (of the same scene)? Just so I can get a good feel for what the compromises image wise are like?

What aspect ratio are you ending up with?

Keith Kline · April 1st, 2005, 12:04 AM

Hey Oscar, sorry I haven't posted sooner. I just wanted to say that I'm impressed with your set up. The footage is coming along nicely. I wasn't really expecting much from the water/oil prism adapter, but I must say that I am very impressed with the images so far. I would love to try and make one of these sometime soon. Do you think you could get an even larger squeeze with different angles? I would love to get a compression to do 2.35:1, but I don't know how well it would look once uncompressed. Frankly I'd settle for anything at this point. Do you know about what compression you are getting now? I know you mentioned that to keep the image problems down you were squeezing slightly less than 16:9. Just out of curiosity, how are you figuring out how much to unsqueeze it? Playing it by ear or are you calculating it somehow?

Anyway keep up the good work and keep us posted!!

Oscar Spierenburg · April 1st, 2005, 05:06 AM

Thanks for the feedback.
I must do a test on the exact aspect ratio. I figured to shoot a grid of some kind. That also will show if the compression is equal all over, which seems like it, but at first, before correcting the angles, it compressed much more to the sides.

Keith, a compression of 2.35:1 would be great, but it has to come from thicker lenses. Maybe Aaron knows how to calculate this, but I'll also try to stack my older prototypes together and see what happens. If the compression is twice as high (with 4 lenses), the calculations would be easy.

Keith Kline · April 1st, 2005, 06:15 PM

I wouldn't mind trying to make a 2X squeeze prism like these, but I have no clue how to go about calculating the squeeze size, shape, angles of the prism. If anyone could tell me how to calculate these measurements, I'd be more than willing to take a stab at making something like this.

Keith Kline · April 2nd, 2005, 02:23 PM

I've been thinking about trying to build one of these the past few days. I just was curious about something Oscar, do you think it would work with a wider lens such as a 24mm or so? Have you tried it with a wider lens or just the 50mm? I would think you might have to make the prisms longer/larger to cover the wider area that a shorter lens would cover. Do you think that would that be true?

April 1st, 2005, 12:04 AM	#27
Keith Kline Regular Crew Join Date: Aug 2004 Location: Akron, Ohio Posts: 153	Impressed Hey Oscar, sorry I haven't posted sooner. I just wanted to say that I'm impressed with your set up. The footage is coming along nicely. I wasn't really expecting much from the water/oil prism adapter, but I must say that I am very impressed with the images so far. I would love to try and make one of these sometime soon. Do you think you could get an even larger squeeze with different angles? I would love to get a compression to do 2.35:1, but I don't know how well it would look once uncompressed. Frankly I'd settle for anything at this point. Do you know about what compression you are getting now? I know you mentioned that to keep the image problems down you were squeezing slightly less than 16:9. Just out of curiosity, how are you figuring out how much to unsqueeze it? Playing it by ear or are you calculating it somehow? Anyway keep up the good work and keep us posted!!

March 19th, 2005, 04:06 PM	#16
Aaron Shaw Major Player Join Date: Jul 2004 Posts: 587	Oscar, yeah those extra prism pieces are there to help correct for color aberration. Might be something to try though I'm not sure it's worth the effort. Setup looks nice. You might want to consider putting a normal spherical lens in front of the whole prism construction. You're going to have to balance the compression ratio vs aberrations it looks like. What sort of compression are you getting from the setup with both at 30 degree angles?

March 19th, 2005, 05:34 PM	#17
Oscar Spierenburg Major Player Join Date: Jan 2005 Location: (The Netherlands - Belgium) Posts: 735	Your right Aaron, this might be the balance you are talking about: http://doublecam.250free.com/exact-angles.jpg (these are exact angles.) I checked the aspect ratio of my homemade double camera thing (other tread) which is a bit more than 4:3. So the compression I get with these adjusted angles will be very close to 16:9 and the color aberration is very much reduced. In the image you can see I meant 30° for the lenses themselves. And Aaron, what would a normal spherical lens do? (by the way, thanks for your replies)

March 19th, 2005, 08:20 PM	#18
Aaron Shaw Major Player Join Date: Jul 2004 Posts: 587	Ah! I understand what you mean now. 30 degree angled prisms. Looks like a workable setup :). I'm definitely looking forward to seeing some more screen grabs and footage! Generally, anamorphic cinema lenses house the prisms between lens elements of some sort. You can sort of see an image of a variable anamorhpic lens here (variable because it changes the orientation of the lenses with the turn of the knob): http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&category=4791&item=5756817409&rd=1&ssPageName=WDVW You can't really see the glass but if you look carefully there is a spherical piece of glass under which the prisms are held. I don't know if you will need one or not. It would be an interesting to test run. The lens, I believe, helps focus the light into the prism. You can change the field of view by changing the spherical glass etc.

March 20th, 2005, 06:47 AM	#19
Oscar Spierenburg Major Player Join Date: Jan 2005 Location: (The Netherlands - Belgium) Posts: 735	I see, so maybe if you get the right spherical lenses, the water prisms could be much smaller if they are only to stretch the image collected (if this is the right term)by the front spherical lens. Maybe this means that you'd have to focus the lenses apart from the normal lens? In my (current) case that's not necessary. I'm definitely going to test a lot the coming days and post the results. EDIT: Oh, one more thing, maybe someone knows. It seems the lenses compress the image a bit more to the sides. Maybe there is a way, or better, a plug-in for after effects to stretch it more to the sides. Or less in the middle of course.

March 27th, 2005, 07:59 AM	#20
Oscar Spierenburg Major Player Join Date: Jan 2005 Location: (The Netherlands - Belgium) Posts: 735	I had to make the small (round) lens over again and made a new one with straight pieces of museum-glass. To begin testing, I made a rail system to mount the whole thing on. The first two pictures on my site show my (very big) setup: http://doublecam.250free.com/ The whole thing has to be covered with something, of course. Maybe some sunshades (flags?) too.

March 27th, 2005, 08:24 AM	#21
Leo Mandy Major Player Join Date: Dec 2004 Posts: 749	Oscar, what is the small silver thing that is hanging from the Lens? It looks like a silver pointer stick or something....

March 27th, 2005, 08:48 AM	#22
Oscar Spierenburg Major Player Join Date: Jan 2005 Location: (The Netherlands - Belgium) Posts: 735	It's a (are, actually) bolt(s) attached to the rear lens to adjust the angle if needed. In the top image, you can see another bolt in sleeve, this is to adjust the angle of the whole lens. Maybe I'll 'tune' the angles (for color aberration) with the camera hooked up to a big monitor.

March 27th, 2005, 06:31 PM	#23
Oscar Spierenburg Major Player Join Date: Jan 2005 Location: (The Netherlands - Belgium) Posts: 735	Here is a new test frame (anamorphic lens and double-cam): http://doublecam.250free.com/anamorph6.jpg I still have too much color aberration on the right side of the frame. It's very much visible (like a red blur)on the edge of the right can. I hope I can get rid of this by adjusting the angle of the rear water lens.

March 29th, 2005, 05:22 PM	#24
Oscar Spierenburg Major Player Join Date: Jan 2005 Location: (The Netherlands - Belgium) Posts: 735	Anamorphic people, I'd like you to check out my new test, because it's a compromise between the compression (16:9) and the color aberration. I've adjusted the angles of the lenses to the camera lens and came up with almost no color shifting (also meaning a slight blur all over) But the aspect ratio is quite a bit less than 16:9. Here's the frame grab: http://doublecam.250free.com/beer.jpg This is before I adjusted the lenses: http://doublecam.250free.com/anamorph6.jpg If the top link doesn't work, click on the first text on my site: http://doublecam.250free.com/

March 31st, 2005, 08:34 AM	#25
Oscar Spierenburg Major Player Join Date: Jan 2005 Location: (The Netherlands - Belgium) Posts: 735	http://doublecam.250free.com/kom.jpg

March 31st, 2005, 07:11 PM	#26
Aaron Shaw Major Player Join Date: Jul 2004 Posts: 587	Those look surprisingly good :) ! Great work! Any chance you could post a shot with and without the adapter (of the same scene)? Just so I can get a good feel for what the compromises image wise are like? What aspect ratio are you ending up with?

April 1st, 2005, 05:06 AM	#28
Oscar Spierenburg Major Player Join Date: Jan 2005 Location: (The Netherlands - Belgium) Posts: 735	Thanks for the feedback. I must do a test on the exact aspect ratio. I figured to shoot a grid of some kind. That also will show if the compression is equal all over, which seems like it, but at first, before correcting the angles, it compressed much more to the sides. Keith, a compression of 2.35:1 would be great, but it has to come from thicker lenses. Maybe Aaron knows how to calculate this, but I'll also try to stack my older prototypes together and see what happens. If the compression is twice as high (with 4 lenses), the calculations would be easy.

April 1st, 2005, 06:15 PM	#29
Keith Kline Regular Crew Join Date: Aug 2004 Location: Akron, Ohio Posts: 153	I wouldn't mind trying to make a 2X squeeze prism like these, but I have no clue how to go about calculating the squeeze size, shape, angles of the prism. If anyone could tell me how to calculate these measurements, I'd be more than willing to take a stab at making something like this.

April 2nd, 2005, 02:23 PM	#30
Keith Kline Regular Crew Join Date: Aug 2004 Location: Akron, Ohio Posts: 153	I've been thinking about trying to build one of these the past few days. I just was curious about something Oscar, do you think it would work with a wider lens such as a 24mm or so? Have you tried it with a wider lens or just the 50mm? I would think you might have to make the prisms longer/larger to cover the wider area that a shorter lens would cover. Do you think that would that be true?