Anamorphic prism adapter that works with 35mm adapter idea...why not like this? at DVinfo.net

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Old March 20th, 2006, 01:36 PM   #1
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Anamorphic prism adapter that works with 35mm adapter idea...why not like this?

Ok, so I've seen some people trying to use prism based adapters, but most people seem to be putting them in front of the 35mm lens, or in between the lens and the ground glass. Why?

Is there any reason something like this wouldn't work:

http://joshuanitschke.saber-x.com/fo...orphicidea.jpg

It seems like it'd be so much simpler, after you focus your camera and zoom in, you wouldn't have to ever worry about the focal lengths changing or anything.

Is there something basic I'm missing about this? It seems pretty simple; I can't have been the first to think of doing it this way, so I'm sure it won't work for whatever reason.

The prisms work like this for people unsure of what I'm talking about. As long as the prisms aren't coated, they'll work with any wavelength, right?
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Old March 20th, 2006, 01:54 PM   #2
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Anamorphic prism pairs play no part in flipping an image, and are therefore useless in a 35mm adapter situation. Also diffusing an image twice with two GGs is just silly and totally bogus. Try reading up on the basics of 35mm adapters first:

http://en.wikipedia.org/wiki/Depth_of_field_adapter

Then you may understand more clearly that no adapter is "based" on prisms, they are merely used to flip the image right-side up.
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Old March 20th, 2006, 02:03 PM   #3
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Quote:
Originally Posted by Ben Winter
Anamorphic prism pairs play no part in flipping an image, and are therefore useless in a 35mm adapter situation. Also diffusing an image twice with two GGs is just silly and totally bogus. Try reading up on the basics of 35mm adapters first:

http://en.wikipedia.org/wiki/Depth_of_field_adapter

Then you may understand more clearly that no adapter is "based" on prisms, they are merely used to flip the image right-side up.
I think we have a misunderstanding.

I want anamorphic. Squeeze the image. Like this adapter Panasonic made did clicky

I don't care about flipping the image, I want to use my full CCD surface to make a widescreen image.

I didn't mention anything about flipping the image or making my own 35mm adapter, please read my post. I want an anamorphic adapter.

Quote:
Also diffusing an image twice with two GGs is just silly and totally bogus
I said I didn't know if it'd need it or not to focus on the image coming through the anamorphic prism set....if it doesn't, obviously I wouldn't. However, if it's the only way to get my widescreen, I'd consider it.
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Old March 20th, 2006, 02:11 PM   #4
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Ahh. Gotcha. Yeah I suppose that would work. Although you definately couldn't get away with two focusing screens.
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Old March 20th, 2006, 02:12 PM   #5
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Quote:
Originally Posted by Ben Winter
Anamorphic prism pairs play no part in flipping an image, and are therefore useless in a 35mm adapter situation. Also diffusing an image twice with two GGs is just silly and totally bogus. Try reading up on the basics of 35mm adapters first:

http://en.wikipedia.org/wiki/Depth_of_field_adapter

Then you may understand more clearly that no adapter is "based" on prisms, they are merely used to flip the image right-side up.
Actually he wasn't talking about flipping the image in any way shape or form. Before making rude comments to someone on the board for just asking a question maybe you should read up on the basics first...

http://www.dvinfo.net/conf/showthread.php?t=38336

Not trying to bash you here, but I find it ironic that you're telling this guy to read up on the basics when he obviously has. This place is for people to gain information not be criticized for asking questions.
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Old March 20th, 2006, 02:20 PM   #6
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Joshua

I think there is alot of things that could be experimented on with this idea. I know Oscar and I had planned on a few experiments with mouting the prisms behind the prime lens instead of in front of the adapter itself. I'm not sure which would be better tho mounting it infront of the GG or behind. I think adding a second GG to the mix would cause more problems than it would solve, but it's worth a shot. I think having the prisms inside of the adapter instead of infront of the adapter itself would make things much easier, but it's getting everything in there and working that's the problem.

I still plan on going back to the idea in the near future, but right now just working on perfecting my adapter itself.
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Old March 20th, 2006, 02:26 PM   #7
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Thanks Keith.

I didn't make my own adapter, I pre-ordered the Brevis35 which Dennis Wood has shown here I believe; I didn't really want to fiddle inside it, you know?

But if you see no reason why the "behind the GG" solution wouldn't work, I'll have my dad cut me some clear glass (he does stained glass) to make into prisms which I'll use for testing purposes (or maybe go to the store and buy some cheap wedge prisms).

If it works out, I'll let you know.

Another reason I wanted to put the anamorphic behind the ground glass was to eliminate the focal lengths changing issue.

Last edited by Joshua Nitschke; March 20th, 2006 at 03:02 PM.
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Old March 20th, 2006, 03:19 PM   #8
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I do remember seeing a thread somewhere about this. Oscar, did something like this, right? Is his webpage still up?
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Old March 20th, 2006, 03:25 PM   #9
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Quote:
Originally Posted by Keith Kline
Actually he wasn't talking about flipping the image in any way shape or form. Before making rude comments to someone on the board for just asking a question maybe you should read up on the basics first...
Thank you, I realized that after his second post. I wasn't trying to be snippy to him, I just didn't realize his intentions.

Quote:
Originally Posted by Keith Kline
Not trying to bash you here
Yes you are. Great job!

I've contributed a lot more to this board than you have and I find it ironic that you bash me and then say you're not trying to. There's a difference between being unknowingly unhelpful, and just being rude. What side are you on?
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Old March 20th, 2006, 03:38 PM   #10
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Quote:
Originally Posted by David Delaney
I do remember seeing a thread somewhere about this. Oscar, did something like this, right? Is his webpage still up?
I read it, but his was in front of the 35mm lens.

Like I mentioned in my previous posts, I only saw solutions where the anamorphic prisms were in front of the 35mm lens, or in between it and the diffusor.

I also saw one design where one prism was in front of the diffusor and the other was behind it which made no sense to me. :)

Not knowing the first thing about optics, I was wondering if there is a reason for that, and why nobody put it behind the diffusor and in front of the camera.
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Old March 20th, 2006, 03:45 PM   #11
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Ben

All i did was point out the fact that you were rude for no reason. I'm sorry but this statement...

"Also diffusing an image twice with two GGs is just silly and totally bogus. Try reading up on the basics of 35mm adapters first"

...was completely uncalled for.

Please point out what I said that was incorrect?

I will state again this is a place for people to learn about these adapters. Everyone here started someplace and I really think that you would have been p*ssed off if the first question you asked to this board someone would have replied with "that's silly and bogus. try reading up on the basics of 35mm adapters first".
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Old March 20th, 2006, 03:53 PM   #12
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Joshua, I don't recall what ever happened to the anamorphic idea tha aaron was working on, but recall his would have went between the prime lens and the GG. Oscar mentioned trying to get his behind the prime lens, but I'm not sure if he's attepted that or not. I haven't seen the idea of one in front and one behind the GG, doesn't make any sense to me either.

The reason I dislike the between the prime and GG is the fact that it changes the Focal Length. It would be alot smaller than the front mounted version, but i'd rather keep the FL the same.

I think the behind the GG might work, but I'm not sure. Oscar would be the best one to ask. I'm planning on making a new set of front mounted prisms soon, so maybe i'll try and test it from behind. Nice thing is the prisms could be ALOT smaller.
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Old March 20th, 2006, 04:09 PM   #13
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"Nice thing is the prisms could be ALOT smaller."

For sure, that's another reason I favor trying this out.

The only thing I'm concerned about is how it will alter focal point...

A lens focuses light, but the prism is mearly squishing it; so will you still have the camera lens focused on the GG? If so, then that'd be cool, but I have a feeling it doesn't work like that. :)

Once my adapter comes, I'm gonna start experimenting with it, unless Oscar or Aaron or somebody says this won't work and satisfies me with reasons why.
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Old March 20th, 2006, 04:19 PM   #14
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If you try to put it between the camera and GG on the Brevis35, I wish you luck. First, what camera are you going to use? can your camera focus on something smaller than 24x36 at closer range than the Brevis35? If not, it's not going to work. The set of 2 prisms will narrow your 24x36 frame and also shorten the light path from camera to GG. The 2 GG idea is not going to work because of 1 simple reason, the prisms will only bend light paths, not focusing them. The best way is to put it in front of your SLR lens. You will also get wider field of view thos way. Thanks.

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Old March 20th, 2006, 04:32 PM   #15
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Originally Posted by Quyen Le
First, what camera are you going to use? can your camera focus on something smaller than 24x36 at closer range than the Brevis35? If not, it's not going to work.
DVX100B.

I was anticipating maybe having to use an "extension" tube, and perhaps a macro.

Quote:
The set of 2 prisms will narrow your 24x36 frame and also shorten the light path from camera to GG.
Dennis Wood said he'd reingeneered the Brevis slightly to make the adapter more favorable for 16:9 cams, so the narrowing may not be a huge problem.

Also, if the prism doesn't refocus the light, then why does it matter if the prisms take up a bit more space? Just zoom in a bit further, or add a more powerful macro, and it should still work, no?

The problem with mounting outside the 35mm lens is that it screws with how you can use them; I want a solution without all those side effects.
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