Cooke lens questiona

[Seth Marshall]

I don't get to play with Cookes too often, though I love the look.

Many people here and elsewhere also love the Cooke look and one of the defining features is the way the focus falls-off or rolls-off. In fact Cooke's website has their own unique depth of field charts.

1.) Speaking strictly regarding this depth of field / focus characteristic, on paper would this effect be the same as stopping down on a non-Cooke lens?

2.) What specifically about the Cooke lens design contributes to their signature look? Are there particular elements or designs they use? (i.e. Planar, Sonnar, Distagon, if not can you explain?)

THanks in advance

 

[Ryan Patrick O'Hara]

You ought to look up a fellow Marshall.


Ian Marshall is hired by Cooke as a lens consultant. He had a large role, from what I can tell, making the recent lines of Cooke spherical lenses.

He would be a good one to ask. He's probably not that hard to find online and I know he's been active and open with sharing knowledge from his past appearances in CML and other places.


John Maxwell is another person you could try and contact as I believe he is another lens consultant/ optical designer who works with Cooke.

Here is an article he wrote that might help:

http://www.fdtimes.com/2013/01/14/jon-maxwell-on-the-cooke-look/

 

[Phil Holland]

I don't get to play with Cookes too often, though I love the look.

Many people here and elsewhere also love the Cooke look and one of the defining features is the way the focus falls-off or rolls-off. In fact Cooke's website has their own unique depth of field charts.

1.) Speaking strictly regarding this depth of field / focus characteristic, on paper would this effect be the same as stopping down on a non-Cooke lens?

2.) What specifically about the Cooke lens design contributes to their signature look? Are there particular elements or designs they use? (i.e. Planar, Sonnar, Distagon, if not can you explain?)

THanks in advance

1. Nope. The the concept of DOF is somewhat uniform across lenses. The focus character itself is different for all lens designs however. Specifically when taking into account center, field, edge, and corner performance.

2. Cooke lenses are spherical and because of that they experience things like barrel distortion, which has a slightly bulbous quality and creates a somewhat "3D effect" (that's what some people call it), whereas some lenses are designed to be flatter and more 2D which are ideal for plane separation. There is no right or wrong answer between those differences as that's a preference thing. Part of the allure of the more spherical effect is it's somewhat similar to how we draw perspective with our own eyes. This distortion comes into play when focusing on your subject matter and how it falls off into the out of focus bokeh. You can see in the focus pull on Cooke S4 and Mini S4 this "growing" effect that favors the center frame due to the spherical design. This also is something that lands in the "breathing" territory to a degree. All of this adds up to "dimensionality" (a term many use to describe this), more or less what that means is an exaggerated effect on spatial separation on content in frame for both in and out of focus content. Focus pulling or racking focus really shows off this effect. The optical design itself lends to a bit of it when it comes down the glass itself and even the coatings, you tend to get a slightly warmer image out of Cookes, which some like specifically when dealing with highlight roll-off and tonality found in common skin tone exposures.

 

[Ryan Patrick O'Hara]

I have heard many rumors, in layman terms, on why and how these lenses are different. Some say it's the way light is bent coming through the unique iris shape, others say the look is from special coatings that favor skintones and orange hued light, others say it's because the modern Cooke lenses are still polished on the same style machine Cooke was polishing lenses with in 1913, an older and more traditional method of lens polishing compared to newer methods today. Maybe all these factors explain the look?

Who knows! Maybe the fellows mentioned above can spill the beans.

 

[Clayton Burkhart]

There is another reason for the Cooke look. The coatings most related to skin tones have a slight flare or halo to them. The other coatings related to Green and Blue do not. What this means in practical terms is that skin gets smoothed out while detail in other parts of the spectrum do not. This is also why there is a slightly warmer look to the lenses. The skin is undergoing a kind of smoothing if you will, yet the details of a face like the eyes, hair, etc. do not.
While many people might not know the difference between a Cooke and other lenses on set, I can assure you that many aging starlets do.

 

[Phil Holland]

I have heard many rumors, in layman terms, on why and how these lenses are different. Some say it's the way light is bent coming through the unique iris shape, others say it's because the modern Cooke lenses are still polished on the same style machine Cooke was polishing lenses with in 1913, an older and more traditional method of lens polishing compared to newer methods today.

Who knows! Maybe the fellows mentioned above can spill the beans.

Thanks for the article link above.

As I've gone down this wild twisted road looking at and using all of the modern and classic cinema lenses I personally think "everything" comes into play when it comes down to it. Quantifying it for creative purposes is often what we discuss here on the boards and with other shooters, but I do enjoy the gross details of wavelength correction and the subtle mysteries found in lens coatings.

The thing is that there is a "Cooke Look" and it's a look that stays consistent across their series of lenses and it's a look that some enjoy a lot. However, there is also a Zeiss Look for sure that can be experienced across their cinema glass lines, particularly the Master Primes and Ultra Primes. The Leica Look exists, but many here think of the Leica-R look when describing it. The Summilux-C and Summicron-C primes are both separate from that and themselves, though they are somewhat based on that heritage. Pretty much all glass has some sort of character that defines it. Some companies are better at making a consistent "set", it's hard to make consistent "series" however.

It's commendable that Cooke throughout it all has maintained something that works across their S5, S4, Mini S4, and to a slightly similar degree their recent anamorphic offerings. Though those to me are a bit different obviously. This is actually something most manufacturers have never been able to achieve.

 

[Ryan Patrick O'Hara]

1. Nope. The the concept of DOF is somewhat uniform across lenses. The focus character itself is different for all lens designs however. Specifically when taking into account center, field, edge, and corner performance.

2. Cooke lenses are spherical and because of that they experience things like barrel distortion, which has a slightly bulbous quality and creates a somewhat "3D effect" (that's what some people call it), whereas some lenses are designed to be flatter and more 2D which are ideal for plane separation. There is no right or wrong answer between those differences as that's a preference thing. Part of the allure of the more spherical effect is it's somewhat similar to how we draw perspective with our own eyes. This distortion comes into play when focusing on your subject matter and how it falls off into the out of focus bokeh. You can see in the focus pull on Cooke S4 and Mini S4 this "growing" effect that favors the center frame due to the spherical design. This also is something that lands in the "breathing" territory to a degree. All of this adds up to "dimensionality" (a term many use to describe this), more or less what that means is an exaggerated effect on spatial separation on content in frame for both in and out of focus content. Focus pulling or racking focus really shows off this effect. The optical design itself lends to a bit of it when it comes down the glass itself and even the coatings, you tend to get a slightly warmer image out of Cookes, which some like specifically when dealing with highlight roll-off and tonality found in common skin tone exposures.

Hey Phil, although most of the above is accurate, I would hesitate to explain to the OP that the overall look of Cooke lenses would be highly in part to the mild distortion. You are making a very good point about geometric distortion and the same point made by Shane Hurlbut http://vimeo.com/90168989 in a recent test of his.

And yes, while there is a noticeable difference, upon comparison, between the Cooke S4's, and the brand new, renowned flat-field Summilux C's, I would say that making the judgement that Cooke's distortion is a defining characteristic of Cooke would be the wrong message to walk away with. As the Summilux C's are probably one of the most flat field primes sets out there, many cine lens sets when compared to them would seem to have increased distortion.

The OP is asking about what Cooke does to make the lenses look the way they do. You seem to make a point that it was because they were spherical.... but with the exception of anamorphic lens elements and the few/rare aspherical lens sets such as SummiluxC and Master Primes, most professional PL lenses are spherical design and all lenses, even aspherical experience the different amounts (depending on design) of distortion, many cinema lens sets are not very different from Cooke's (regarding distortion levels.)

I suppose my understanding is that Cooke isn't purposefully adding distortion to the lenses, nor are they purposefully avoiding removing distortion for the sake of a 'look'. It is my understanding that they do their best, like everyone else, to eliminate as much geometric distortion as possible and the end result is in the same neighborhood as other lenses. In fact, once you get to 32mm+ in the Cooke Mini's, the amount of distortion is unnoticeable from higher performing flat field sets like aspherical Summilux C's.

I would hesitate to say Cooke's look is from barrel distortion when their lenses are basically on par with other typical spherical cine lens sets. If anything it's the Summilux-C lenses have a distinct look based on their absence of the typical and mild distortion cinema lenses have! hahaha.


Distortion is certainly a good point, but I don't think Cooke stands alone in regards to the amount they have, so it really isn't a definitive characteristic of their lenses, although it is a characteristic.

 

[Phil Holland]

I don't believe it was something initially done purposefully. I think it's what was, is, and always will be with their lenses. Looks like I need to check out my charts again comparing the 32mm, especially at closer focusing distances. Can't even remember now, but I'll grab that hard drive and dig those up.

I agree all spherical lenses exhibit this to a degree, I do think Cooke is rather consistent with it across their sets however. I feel it's part of the character of the lenses and I've been told that from Cooke as well.

Also, gotta say. Just had the 32mm Mini S4 up on a chart a week ago. That lens is pretty banging sharp wide open. It was fun putting it against 35mm Xenons, CN-Es, and CP.2s. It certainly is built like a tank and more ideal for motion picture production in my mind.

 

[Ryan Patrick O'Hara]

Alfonso Parra does some great lens tests and uses proper methods with quantifiable data. His website is down, I believe, but I have all of his PDF's for reference.

The Cooke 32mm MiniS4 had measured barrel distortion of 1.76% while the Summilux-C 35mm he measured 1.56% barrel distortion.

However, the Cooke 25mm was 2.41% distortion while the Summilux 25mm was 1.29% barrel distortion.

The 18mm Cooke Mini, is the worst at 4% distortion, while the Summilux 18mm is also the worst of the set at 2%. This is pretty telling.



I wish I could test lenses the way he does. He's on the next level.


Note these figures are for Mini's. The S4's although matching very closely, are different set of lenses and those distortion figures are not known at the moment.

 

[Seth Marshall]

Thanks so much for all your feedback, it has been helpful. Regarding my first question. I completely understand the physics of optics are defines DoF, but want a better understanding as to WHY COOKE LENSES seem to have a gentler roll-off / fall-off. From the ways people describe one could almost assume it were similar to stopping down on another lens--- but I know this isn't the case. Still, there must be an explanation for this fall-off being different. And if one were to compare it to another lens stopped down how would it be different? I wish I had the capability to do test like this myself. Still, is seems to be fact that their lenses roll-off gentler than say CP.2s. I would very much like to see this side-by-side and then try to match by stopping down the Zeiss and seeing how that compares. You understand?

Then regarding less design, which very much may be the direct explanation for the above behavior, what about Cooke lenses are different? (other than coatings, as has been mentioned). disclaimer - I know that answer to this may be way over my abilities and is much more for an engineer, yet I still feel comparisons with similar lens designs will help illustrate what I hope to understand. Thank you

 

[David Mullen ASC]

I think you are over-thinking this issue, it's not like you'd get a Cooke to look like a Zeiss in terms of DOF by opening up by a whole stop or something, the fall-off difference is not as radical as you seem to be suggesting nor is the difference in DOF.

The general way to think about this is that a lens that is lower in contrast looks slightly softer (because contrast and visual sharpness are related) and therefore tends not to "snap" into sharp focus as cleanly or dramatically as a more contrasty lens. This also has the effect of making the DOF seem greater because the in-focus area is not as dramatically tack-sharp compared to the out-of-focus area. But in terms of actual depth of field, which is not how a sharp foreground looks compared to a soft background, but refers to the distance range where a subject looks acceptably in-focus, I don't think of a Cooke as having much of a measurable difference compared to some other lens.

 

[Seth Marshall]

Good explanation. I never knew the Zeiss' were more contrasty than the Cookes. But certainly the Zeiss has the snap you speak of.

 

[Jacek Zakowicz]

2. Cooke lenses are spherical and because of that they experience things like barrel distortion

Phil,
I'm pretty sure that by "spherical" they mean "non anamorphic" - not "non aspherical"
Besides- you can make "non aspherlical" lens designs with little to no distortion- they are just bigger - pretty much the way MPs and S4s are...

 

[Les Hillis]

...I completely understand the physics of optics are defines DoF, but want a better understanding as to WHY COOKE LENSES seem to have a gentler roll-off / fall-off...

I think the article that Ryan linked to explains where some of the subtle differences in 'looks' between lenses are coming from. In that article they describe some of the elements/variables that are actually being adjusted when they design a lens, some of which would have an effect on the perceived roll-off/fall-off of a lens.

I'm not sure how much adjusting is done in a lens design purely to address the roll-off/fall-off characteristics in and of themsleves, but if you look at the roll-off/fall-off as being just as much a result of where the focus is coming from and going to, as much as it is about the actual area in-between those two points, then you can imagine how easy it would be to have the overall design of a lens influence that roll-off/fall-off area.

I'm tending to think, based on that article Ryan posted, that Cooke put a lot of effort into getting their focal and achromatic planes aligned, and that they do it while also adjusting astigmatism to get their off-axis areas corrected. Which would suggest that the roll-off/fall-off would also benefit from that, if it exists in-between those two nicely corrected points.

Or I could be wrong lol.

I do like the Cooke look though, thanks for raising the subject and reminding me of it.

 

[Phil Holland]

Phil,
I'm pretty sure that by "spherical" they mean "non anamorphic" - not "non aspherical"
Besides- you can make "non aspherlical" lens designs with little to no distortion- they are just bigger - pretty much the way MPs and S4s are...

Sure. I'll just say it this way instead. Cooke lenses utilize a spherical design and due to this they experience distortion and aberrations commonly found in spherical lenses.

Yes, you can go the Zeiss route and use the larger elements eliminate much of the distortion within field.

 

[Seth Marshall]

You right, that article really does tackle the question I had. I guess it's this careful attention to aligning those planes that allows this characteristic. It makes sense a lens with different design priorities would appear to snap at critical focus considering chromatic aberrations may be more pronounced immediately after that "sharpest image plane". Not sure if I'm speaking the correct terminology, but I'd like to think it's beginning to make sense!

The only mystery is with such a winning design why haven't other lens manufacturers started copying this technique!

 

[Les Hillis]

Yeah, it makes sense, not that I know much about it myself.

It's also mentioned in the article that the actual assembly of the lens plays an important part in the final result. Which pretty much means hand-assembling and manually checking to see if everything's come together properly, and correcting it if it hasn't. That's not an approach that lends itself to mass production, or the sort of operation that could be set up very easily. Likewise with the other pains-taking aspects of research, development and production that companies like Cooke and Leica and Zeiss etc. undertake. Some of those processes have been refined for over almost a century. So, yeah, it's understandable if there aren't a lot of other companies doing it.

 

[Ryan Patrick O'Hara]

The only mystery is with such a winning design why haven't other lens manufacturers started copying this technique!

I would imagine Cooke is not openly copied for many reasons.

1st, I'd hope that Cooke has some sort of legal protection on their designs and methods. Standard business, really.

2nd, Manufacturing precision optics is likely the most difficult production line of any product made for cinematography markets, which are small and niche. Making lenses is incredibly expensive and difficult. Not many are willing to gamble that much investment to simply copy someone else. I imagine finding working D-type polishers from 1913, the skilled workforce, and the 100+ years of infrastructure and experience would be the hardest part.

3rd, There really isn't that many companies who continuously make cinema lenses. Schneider, Zeiss, Canon, Leica, Fujinon and Angenieux. The latter two are currently zooms only. All of these lenses have subtle differences which make them ideal in different situations. It would be a less interesting world if they all looked the same, even if they all looked like beautiful Cookes.

 

[Clayton Burkhart]

I would imagine Cooke is not openly copied for many reasons.

1st, I'd hope that Cooke has some sort of legal protection on their designs and methods. Standard business, really.

2nd, Manufacturing precision optics is likely the most difficult production line of any product made for cinematography markets, which are small and niche. Making lenses is incredibly expensive and difficult. Not many are willing to gamble that much investment to simply copy someone else. I imagine finding working D-type polishers from 1913, the skilled workforce, and the 100+ years of infrastructure and experience would be the hardest part.

3rd, There really isn't that many companies who continuously make cinema lenses. Schneider, Zeiss, Canon, Leica, Fujinon and Angenieux. The latter two are currently zooms only. All of these lenses have subtle differences which make them ideal in different situations. It would be a less interesting world if they all looked the same, even if they all looked like beautiful Cookes.

Actually, this is not exactly the case. Most of the companies that make lenses, coatings, etc. you never have heard of. Zeiss is more like Nike than Cooke. They design, but they don't manufacture much these days. Cosina is only one of many factories/suppliers that they work with for instance.

However, I will only mention it once more. For me Cooke is less about the mechanics, than it is about the coatings. In fact this could be said of almost all the manufacturers today, including Canon. We have known how to grind perfect lenses for a very long time. However, the real signature is in the design for their transport in a metal tube and the coatings. Most of what people attribute to Cooke is actually that level of flare in their coatings related to skin tones. This is what gives the softness, while the other layers retain sharpness. No other manufacturer does this.

 

[David Mullen ASC]

Zeiss probably feels they make an excellent product without having to copy Cooke. Some of this is just a matter of taste.