How Do Anamorphic Lenses Work?

T

tommygdawg

Well-known member
Hey all,

I've been curious about this for sometime. I know that anamorphics squeeze the image horizontally, but I was curious as to how exactly they do this. Also, what is the difference, mechanically, between focus-through anamorphics and anamorphics that require you to focus both lenses at the same time? How are anamorphic primes made that are stand-alone lenses and don't need to be attached to other lenses? Just curious out of interest to learn. Any info would be greatly appreciated.

Thanks!
- Tommy
 
It's an interesting read no-doubt. However, I know the basics of working with an anamorphic lens. I was just curious as to what goes into actually constructing an anamorphic lens. For instance, that article talks a lot about the placement of the anamorphic element. Is what makes a lens anamorphic, simply a single piece of glass placed at a certain point in the lens? What exactly about the glass makes a lens anamorphic?
 
There are lot of different anamorphic lenses designs.
Generally speaking (in the simpler form) the basic difference with a spherical lense is the use of crossed cylindrical lenses (plano concave lens + vertically placed plano convex lens).
A focus through lens has a fixed distance between these two elements, thus "focusing" better at a particular distance, which makes sense for projection. That is why all these lenses, when used for filming operate better at stopped down apertures (deep dof).
An anamorphic with a "focusing ring" is able to modify the distance between the cylindrical elements, thus making it more sensible to selective focus at various distances. Hence better for filming.
There are also lenses with prisms and mirrors.
 
The basic principle is similar to the crazy mirrors at the fairground. Instead of a spherical lens it is cylindrical. In fact some of the earlier designs such as the Delrama and Vistascope (Old Delft) did use a curved mirror combined with a prism which I believe is to correct the chromatic abberation. I have a Delrama and I'm guessing it is due to the mirror design that it loses a stop more light than my other anamorphics. I've also found it to be very resistant to the desirable kind of flares commonly associated with anamorphics. It also produces a somewhat softer image, this may be down to the need to fully open the aperture of the taking lens and/or the presence of some spots on the prism. The upside to the Delrama is that it is 1.5x squeeze, light weight and small form factor.

I also have a UltraPanatar which uses a prismatic design. This works using two prisms angled to each other to squeeze and correct the image using refraction. You can make your own DIY one using this principle using wedges of crystal (home projector enthusiasts save thousands doing this) although results will likely not match that of a proper one. The prismatic anamorphic design is not only focus through but usually features a means of changing the angle of the two prisms, making the squeeze factor variable. Mine is adjustable anywhere from 1x to 2x squeeze factor. It was originally meant for projectors and meant the projectionist didn't have to change lenses between movies. The down sides of this design is that it is soft at the sides (more so in the corners - kind of like a sharpness vignette), minor colour abberation and that the unit is rather large. My tripod is already groaning under the weight of my rig so I haven't fully tested this one yet but I doubt it would produce the trademark flares. From the testing I have done it produces a nice retro 70s look with a softer slightly washed out look. At a distance of 3ft from the bookshelf softness and CA made text unreadable but stopping down produced sharp text on DVD spines. Looking forward to playing with this one more, the guts of this lens are in a single unit that can be removed so I might rehouse it in a PVC pipe to reduce weight.

The common design is using a cylindrical lens principle rather than a spherical lens. You can see the basic effect by looking through a cylindrical drinking glass, the refractive distortion will squeeze the image horizontally. The anamorphic lens is slightly more complicated to correct for unwanted distortions (just as the spherical lenses use a multi element design) but the principle is essentially the same as the drinking glass illusion. There is no oval shaped element in the lens, what you are seeing is the circle at the other end distorted by the optics. I believe the common cylindrical design was invented by Henri Chretien in France and called Hypergonar. I'm not completely sure what the design difference between a focus through and a focussing anamorphic lens is but I suspect that focus through uses a simpler 2 element design and the focussing ones use more elements but that is largely (well completely) a guess on my part. I'm mainly basing this assumption on a reference to the non-focussing Hypergonar making specific mention of having a double element.

I am not aware of any other design. There is the anamorphic prime but this is simply a cylindrical lens with the spherical taking lens built into the unit. You are right to ask for this information because it seems that there is a conspiracy of secrecy surrounding anamorphics. There is so little information out there it is astounding. Everything I've said here is pretty much everything I've learnt after more than 6 months research and I can't attest to the accuracy of anything I've said, it's pieced together from a throwaway comment in a forum here, a sidenote in an article there and from simply examining the lenses I have. The prismatic stuff is the most accurate because, well you can see exactly how it works just from looking at it (I have completely dismantled and rebuilt mine - it's a very simple design). I have a PoS Superama that I got thrown in with a lot at auction last week (with a mint Sankor 16c and good condition Singer 16d) which I'm willing to destroy in the name of research. So I plan on taking it apart on the weekend if I have time unless the weather's good in which case I'm doing some shooting. I'll report back after I've had a look inside.

EDIT: Kostas snuck in before me...and managed to say pretty much the same thing in a succint 8 lines!
 
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Thank you so much for the information, both of you. Egg Born, you may have repeated what Kostas said, but between the two of you I was able to get a lot out of the information. What you said helped clarify some of the things he said, so it all works out :) I really wish there was more info on anamorphics, I find the concept of them quite interesting and I hate not knowing how things work.

Kostas, you said:
Generally speaking (in the simpler form) the basic difference with a spherical lense is the use of crossed cylindrical lenses (plano concave lens + vertically placed plano convex lens).
Click to expand...
What do you mean "crossed cylindrical elements?" I looked up those two types of lenses and found some images and diagrams, which is cool. But, I don't don't understand what you mean by crossing them. Would you mind elaborating more? Thanks!

Out of interest, how does one come into cylindrical lens elements? Is it basically a spherical lens element with an oval-shaped internal barrel?

EDIT:

I think I'm beginning to understand. Maybe! The internal barrel (or whatever it's called) of an anamorphic isn't actually oval shaped? The cylindrical elements at the front and the back just make it appear so? (I realize you said this, Egg Born...but it just now clicked :P). Is an anamorphic lens essentially constructed like this? http://en.wikipedia.org/wiki/File:CylindricalLenses_2.png
 
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That looks about right. The one on the right looks like the front element anyway. The convex surface at the front and rotated 90 degrees to the image. I'll take some pictures when I take apart my sacrificial superama.
 
Egg Born Son said:
That looks about right. The one on the right looks like the front element anyway. The convex surface at the front and rotated 90 degrees to the image. I'll take some pictures when I take apart my sacrificial superama.
Click to expand...

Awesome, very much looking forward to it!
 
Egg Born Son said:
In the meantime just came across this lens diagram for lomo anamorphic. I don't read russian but the diagram partway down the page is self-explanatory.

http://www.ixbt.com/digimage/anamorf.shtml
Click to expand...

This is a simplified diagram and is based on a projection lens - although the principle is similar for cinema lenses.

Quick google for anamorphic lens diagrams - https://www.google.co.uk/search?q=a...Juy10QXZ-vXbDA&ved=0CGwQsAQ&biw=1920&bih=1115 plenty of good examples :)
 
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MadMonkFish said:
This is a simplified diagram and is based on a projection lens - although the principle is similar for cinema lenses.

Quick google for anamorphic lens diagrams - https://www.google.co.uk/search?q=a...Juy10QXZ-vXbDA&ved=0CGwQsAQ&biw=1920&bih=1115 plenty of good examples :)
Click to expand...

Thanks much! I didn't even think to do that! Basically, from what I'm seeing, the concept behind cylindrical lens anamorphics is fairly simple. Why has no one tried to make a DIY cylindrical lens?
 
It's easy to make a simple anamorphic but hard to correct the issues such as uniformity of squeeze factor (tends to be more stretched in the centre, less at the edges), chromatic aberration, pincushion/barrel distortion, general and uneven softness of image. I know that doublet lenses are used to correct some of these issues because the previous owner of my superama informed me that they boiled the doublet apart to clean out the glue which had gone bad. I expect low demand scuttles any chance of making back the development costs. Other than high end cinematic lenses like hawks the only currently produced ones I'm aware of are for digital movie projectors and cost around $3000 and are too big to be practical. I have an article on building a DIY prismatic anamorphic intended for digital home movie projectors. I priced the build cost at around $200 but haven't gone ahead with it as of yet. It would be no good for taking but for projections the extra screen size outweighs the flaws.
 
Just to clarify what I said about crossed cylindrical lenses.
I meant to say that they have crossed optical axes. Maybe this picture illustrates better this concept.
28009d1278947270-445ld-anamorphic-prisms-jayrob-diy-newport-optics-cylindrical-lens-drawing.gif

Another thing is that you always need a spherical taking lens behind the anamorphic element (either it is natively attached to the anamorphot -see Iscorama, Lomo-, or you use a different taking lens).
I think the main reason there is not much information on anamorphics, is that it is a technical issue that may interest only a restricted audience, and/or not many people have the knowledge to provide accurate infornation on the subject. I have recently seen a 140 pages long French diploma thesis (in french) on the subject of anamorphic lenses!
Most things you learn on anamorphics are through a personal trial and error process, while seeking the anamorphic setup with the less weaknesses, as there is no such thing as the perfect anamorphic.
 
kostas said:
Most things you learn on anamorphics are through a personal trial and error process, while seeking the anamorphic setup with the less weaknesses, as there is no such thing as the perfect anamorphic.
Click to expand...

True that. I learnt more in the first hour or two with my first anamorphic than in the weeks of research leading up to it.
 
Kostas, thanks for the clarification. In that example, two convex cylindrical lenses are used. Is that normal?

The problem with learning based on trial and error is the funds to get into it. I can't really justify spending $100 dollars or more on projection anamorphics that weigh a million pounds and focus to only 30ft, just for trial and error. I've thought about trying to get one of the more common projection lenses that people use, such as Sankor's or Eiki's, but I don't really know if it's worth it.
 
tommygdawg said:
Kostas, thanks for the clarification. In that example, two convex cylindrical lenses are used. Is that normal?
Click to expand...

The image above is not from an anamorphic lens design! This was just to illustrate the "crossed" term. Yes normally one of the two lenses should be concave normally.


tommygdawg said:
The problem with learning based on trial and error is the funds to get into it. I can't really justify spending $100 dollars or more on projection anamorphics that weigh a million pounds and focus to only 30ft, just for trial and error. I've thought about trying to get one of the more common projection lenses that people use, such as Sankor's or Eiki's, but I don't really know if it's worth it.
Click to expand...

Don't get $100 heavy projection lenses! It has already been reported that these are not great for filming other than deep focus landscape shots. When you have the funds, try investing (a bit more than $100) in one of the well known and tested solutions, then build up from there. Anyway, anamorphics hold their value most of the times, so you will eventually not loose much if you decide to resell the lens at some point.
Kowas and Sankors are well known 2x solutions that work nicely, if you want a 2x ratio (3.56:1).
1.5x ratio lenses (2.65:1) are even more expensive, but some of them are well worth the price in my opinion.
Please refer to the "anamorphic Shootout" thread for more details...
 
I have 6 anamorphics including a couple of heavy projection lenses, a Sankor 16c, Singer 16d that I haven't had the chance to play with much yet ($280 for both), and my current favourite a Mosty SE that I haven't seen before or since and only cost me $45. The key features I would look out for are:

Look for an anamorphic with a short barrel length and large diameter rear element to reduce vignetting and allow wider taking lenses
Lightweight is better for obvious reasons
Close focussing, most the good ones focus as close as 1.5m/5ft
Rare non-focussing/fixed are supposed to be desirable but I don't have one so I don't know if there are limitations
Names such as Sankor, Singer, Kowa, Elmoscope, Iscorama are safe but with some research, patience and luck you can score a bargain with an unknown brand
Expect to pay $300+ but with some research, patience and a little luck you can get a bargain - I've paid just over $500 for 6 lenses delivered (half are good)

Maybe Kostas can contradict or add to the list, he's been doing this longer than me.

Anamorphics are fun and rewarding but it is worth noting that not a lot seems to get made with them, given how many people are playing with them. The prices are high because demand outstrips supply so where are all the indie anamorphic movies? Far outnumbered by camera tests. Decide how much you are willing to invest for a play.
 
Thanks for the information and links, both of you. I do actually want to shoot short films with anamorphics, I really like the look of it. Sure, from a geeky/techy standpoint, it just sounds like fun, but I really want to actually shoot some movies with it. Any thoughts on where to look for them, aside from ebay?
 
I got all of mine on ebay. I've done very well on price but that is the result of about 4 months checking daily. I got bargains by losing 95% of my auctions by not bidding higher than I was willing to pay. Missed out on a couple that I really wish I'd bid higher on though. The cost of the lens is just the start. Then you need to find a way to mount it, there are some expensive clamps available. My $45 lens had a thread so I bought a CPL rotating filter and pushed the glass out so had a mount for $12. My other ones I've had to buy clamps for, the cheapest $60. I also had to buy lens supports to take the extra weight off the filter threads. Diopters allow you to focus closer but they are going to cost almost as much as the lens. Expect the outlay to get a satisfying combination to end up costing you much more than you plan. You really need to buy a dud or two and have a selection to find the look you want. Once you've got a few you will learn what you need to know and know what you want. The upside is once you find a combination you are happy with you can pop the extras back on ebay and get your money back.
 
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