Anamorphic and Spherical Lens Focusing

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    Lens Optics Spherical
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Discussion Overview

The discussion revolves around the use of anamorphic and spherical lenses in cinematography, specifically focusing on how to achieve a single focus mechanism for both types of lenses. Participants explore various optical arrangements and attachments that could facilitate this process, addressing both theoretical and practical aspects of lens design and functionality.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant describes the challenge of using anamorphic projection lenses in conjunction with prime lenses, seeking a solution to focus both lenses simultaneously.
  • Another participant suggests that an anamorphic attachment can vary in complexity, from simple prisms to more intricate cylindrical lens arrangements, and notes that ideally, these attachments should be afocal.
  • A participant mentions having an anamorphic attachment that focuses from 1m to infinity and seeks advice on what optics could be placed in front to achieve a combined focus.
  • There is a suggestion that two optical elements could be used that are afocal when close together and have specific diopter powers when spaced apart.
  • One participant expresses concern that adding complexity to the optical system may degrade performance, suggesting a bellows-style focusing method as an alternative.
  • Another participant discusses the concept of using a variable diopter to achieve the desired focus range, referencing the construction of such a diopter using plano-concave and plano-convex lenses.
  • A later reply cautions against attempting to create a homemade solution, emphasizing the potential degradation of optical performance and recommending experimentation with existing equipment instead.

Areas of Agreement / Disagreement

Participants express differing views on the feasibility and effectiveness of home-brewing optical solutions, with some advocating for experimentation while others caution against potential performance issues. There is no consensus on the best approach to achieve the desired focusing mechanism.

Contextual Notes

Participants note the importance of understanding the properties of the lenses involved and the potential impact of additional optical elements on image quality. The discussion highlights the complexity of lens design and the challenges associated with achieving specific optical effects.

artiswar
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New to the forum but stumbled upon this and thought it might be beneficial to query more scientifically minded individuals. I am a filmmaker and use a variety of lenses to acquire certain looks. One of which is anamorphic cinematography. (http://www.red.com/learn/red-101/anamorphic-lenses) Expensive ($40K and up) anamorphic primes (anamorphic elements and spherical combined into a single focusing lens) are designed to work with single focus. As a cheap work around, indie filmmakers began purchasing projection lenses (http://petapixel.com/2014/05/07/shooting-anamorphic-lens-dslr/) and using them in conjunction with the prime lens affixed to the body. While it produces the effect, both lenses must be focused. I saw somewhere on the net, where both the anamorphic projection lens and the prime lens were set to infinity focus and optics were attached to focus the two lenses. After all this, my question is, what could be affixed the the front of the lenses to focus both? Apologies if I was unclear.
 
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I think I understand your question, but I'm not sure- do you have an anamorphic attachment already?

In any case, an anamorphic attachment can be very simple (Brewster prism):
http://www.directindustry.com/prod/ealing/anamorphic-optical-prisms-29471-843383.html

to more complicated arrangements of cylindrical lenses:
http://www.iso1200.com/2012/06/most-amazing-anamorphic-diy-adapter-to.html

The basic concept is to have a lens with two focal lengths, with cylindrical elements providing additional optical power along one axis. Anamorphic attachments are ideally afocal, so the 'prime' lens will be unaltered along one axis: squares becomes rectangles, circles become ellipses, etc. Since vid-atlantic (http://www.vid-atlantic.com/lensshop) recommends focusing both the prime and attachment, I suspect the attachment is not entirely afocal.

Does that help?
 
Andy Resnick said:
I think I understand your question, but I'm not sure- do you have an anamorphic attachment already?

In any case, an anamorphic attachment can be very simple (Brewster prism):
http://www.directindustry.com/prod/ealing/anamorphic-optical-prisms-29471-843383.html

to more complicated arrangements of cylindrical lenses:
http://www.iso1200.com/2012/06/most-amazing-anamorphic-diy-adapter-to.html

The basic concept is to have a lens with two focal lengths, with cylindrical elements providing additional optical power along one axis. Anamorphic attachments are ideally afocal, so the 'prime' lens will be unaltered along one axis: squares becomes rectangles, circles become ellipses, etc. Since vid-atlantic (http://www.vid-atlantic.com/lensshop) recommends focusing both the prime and attachment, I suspect the attachment is not entirely afocal.

Does that help?

Close. I have the anamorphic attachment, a lens that focuses from 1m to infinity. Also attached is a prime photography lens (spherical) directly to the body. In the example I saw online, both lenses were focused to infinity and another set of optics were placed in front to focus both lenses with one focus pull of the new optics. My question is what could elements could be affixed to the front of lens system to focus both singly?
 
I guess to clarify, what optics arrangement could be placed in front of the anamorphic lens, which is placed in front of the standard prime that is attached to the camera, to focus both from infinity down to about 1 to 2m and back out to infinity?
 
It seems with some intense research, I need two elements that when close together are afocal and when spaced have a power of .6 or .5 diopter. Any ideas?
 
artiswar said:
Close. I have the anamorphic attachment, a lens that focuses from 1m to infinity. Also attached is a prime photography lens (spherical) directly to the body. In the example I saw online, both lenses were focused to infinity and another set of optics were placed in front to focus both lenses with one focus pull of the new optics. My question is what could elements could be affixed to the front of lens system to focus both singly?

Tough to say- my guess is that the third optical element (the third of: prime lens, anamorph, 'focus controller') will depend on the properties of the other two lenses. My rule (since I'm not a lens designer) is that making the optics more complicated always results in degraded performance.

Alternative idea: what about detaching the prime+anamorph from the camera body and focus view-camera style with a bellows?
 
Andy Resnick said:
Tough to say- my guess is that the third optical element (the third of: prime lens, anamorph, 'focus controller') will depend on the properties of the other two lenses. My rule (since I'm not a lens designer) is that making the optics more complicated always results in degraded performance.

Alternative idea: what about detaching the prime+anamorph from the camera body and focus view-camera style with a bellows?

Thank you for all of the replies! I've been able to narrow down what it is I'm trying to do. As I understand it, focusing both the lens on the camera and the anamorphic to infinity, this produces an afocal block. Mounting a variable diopter in the front allows one to tame the focus back from infinity to something shorter. This is how popular single focus (expensive) anamorphics work. From the constructions I've found, the variable diopter is comprised of a plano-concave and a plank-convex lens that varies the diopter power based on the spacing and the two elements are afocal when touching. I guess my question as it stands now is: Where can I find a formula or the such to figure out the power of the two elements in order to achieve the afocal aspect as well as closer focus?
 
Honestly, I wouldn't recommend trying to 'home-brew' something like that, I'd be surprised if the optical performance of a simple air-spaced doublet would not grossly degrade the imaging performance of your other lenses: field of view, chromatic aberration, coma, ghosts... I do recommend experimenting with what you have, to see if you can achieve the results you are interested in.

There's a reason expensive lenses are expensive.
 
 

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