F&D Times Cooke Tour

7/30/2019 F&D Times Cooke Tour

1/8

June 2007

David Nettleton, Cooke Chie Engineer,demonstrates the robustness o a CookeS4/i. Although the lens survived, youshould not attempt. May void warranty.

Were on the outskirts o Leicester, twohours north o London. Te Cooke ac-tory has relocated rom the Dickensianindustrial revolutionary ancestral homeI remembered to this modern acility onthe outskirts o town.

Inside the actory, there are lm posterseverywhere. Every square inch o avail-able wall space is estooned with posterso major motion pictures: Da Vinci Code,Harry PotterGoblet o Fire, Prisoner o

Azkeban, Kingdom o Heaven, CinderellaMan, Casino Royale, Brokeback Moun-tain, Munich, Te Interpreter, Jarhead,

Apocalypse Now, Chocolat, and more.

It is clear the people who work here lovemoviesespecially ones supplied withCooke lenses. Pat Webb (above) saw 250lms this year in movie theaters. He hasworked at Cooke or 42 years, and is thematerials controller, tracking the arrivaland deployment o countless parts.

Lens design is all about math. Its aboutunneling what you see down a littlehole in your camera. Stung a 24 mileswath o Moroccan desert in Babelontoa 24mm x 18mm piece o plastic requiresa dierent set o calculations than the 10'wide stacked telephoto astronaut heroshot in the Right Stuf. A at piece oglass will pass light (the image) straightthrough. But, look through a raindropon your window and see how the curvedsurace does interesting things.

It became clear afer many centuries opeering through raindrops and othercurved suraces that the way light be-haved could be described in mathemati-cal ormulas.

Cut to Leicester, England. In 1885, broth-ers William and Tomas Smithies aylormoved to Leicester to set up a business as

Manuacturers o Optical Instrumentsin Slate Street.

Cooke Book

Jon Fauer, ASC reprinted from Sundance Issue 9 and Cinegear Iss

The Newsletter of Art, Technique and Technology for Film, Video and Digital Produc


2/8

June 20072

Tis was the Silicon Valley o the Indus-trial Revolution, where an abundanceo coal to power the steam engines thatran the mills ueled the development orailroads, the dimpled gol ball, a knittingindustry that supplied most o the worlds

socks and, o course, camera lenses.

Te aylor brothers were mechani-cal geniuses, having opened their rstworkshop in North London while stillat school. Tey built their own lathe andconcentrated on optical engineering.

In 1881, the aylors built magic lan-terns rom brass and mahogany, withlenses ground by hand rom solid glassblocks. It was actually two projectors,one above the other, illuminated byseparate limelight burners. Tey wereused alternately on the same screen toprovide dissolves and transitions between

slidessomething Powerpoint still does.

An original aylor magic lantern is on

display at the Snibston echnology mu-seum, not ar rom Leicester.

In 1887 William Hobson was takenon as sales manager, and the rm wasnamed aylor, aylor & Hobson. Terst Cooke lens was made in 1894, afer. Cooke & Sons o York (makers o tele-scopes) oered aylor, aylor & Hobsonthe manuacturing rights to a riplett(3-section) photographic lens that solvedthe problem o edge sofness.

Speed-ramp through the next 100 years:almost all eature lms made in Hol-lywood during the rst hal o the 20thcentury were shot using Cooke lenses.Major innovations included the 1921Speed Pancros (2.0), and the rst pro-

duction zoom lens (circa 1936).

Te aylor brothers died in 1937 and

1938the company was renamed ay-lor-Hobson. In 1945, it became a subsid-iary o the Rank Organization, with theamiliar gong logo. Its ounder, J. ArthurRank (later Lord) was the British Moguland Methodist who began by producingreligious lms and wound up controllinghal the theatres in England and most othe production studios.

But, as Ranks ortunes dwindled (a-miliar storymergers, diversicationinto real estate and the Hard Rock Cae)

Cooke lenses became a neglected divi-sion o the company. By the 1990s, therewere reports that the place was so rundown that sea-gull eathers would oatthrough holes in the roo.

Enter Les Zellan. Te Wall Street Journalwrote, In 1998 an American wearing

jeans, a bright yellow shirt and a 20-year-old red tie, with a beard and a short busi-ness plan, rescued the company.

Lens making or motion picture cam-eras is as much an art as a science. Whatmakes it especially interesting is the needto ocus smoothly on actors and thingsthat move during the shot, and the ex-quisite tolerances needed to prevent anydierences between actual eye ocus andocus marks on the lens barrel.

Lenses begin as clear, bubble-ree,

scientic glass. Tis comes rom Schottin Germany and Ohara in Japan. Over70 dierent types o glass are used, withdierent reractive and chemical com-positions. o save time, stress on theglass and waste, they are supplied alreadymolded close to the required shape, withabout 1mm excess. Te outer suraces arerough; you cant see through this glass.Only when ground and polished with

very ne abrasive (cerium oxide) will itappear clearjust as toothpaste makesscratched Plexiglas look clear again.

Grinding with modern CNC (ComputerNumerically Controlled) machines, andalso on the same machines used 90 years

ago, puts precise curves in the glass.

Cooke, contd


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June 2007

Cookes Tour: The Adventure Continues

Weve heard about the history o Cooke, ounded in 1886 by the aylorbrothers, Manuacturers o Optical Instruments and inventors o thedimpled gol ball.

Located in a modern building on the outskirts o Leicester, England,the Cooke actory today employs over 65 highly skilled crafsmen andwomen. While other optical companies around the world make lenses

or many purposes, Cooke still specializes in lenses or the motionpicture industry.

So, lets get started and build some lenses. It only takes about 40 hoursrom start to nish to assemble a Cooke S4/i.

Grinding globs o glass into ne optical-mechanical instruments is ahighly guarded, highly skilled industry matched in secrecy only by thatother high-end grinding business: diamonds.

Tis Cookes tour was the rst time a mortal cinematographer was

allowed unrestricted access with a camera into the inner sanctum andholy o holies o lens creation.

Lens design is mostly math, physics and ormulas. Venerable aylorHobsons and Speed Panchros began as long lines o numbers pencilledinto voluminous notebooks, still on display and ofen reerred to in theCooke design oces. Now they use computers. Paul Nettleton uses 3DCAD, middle lef.

In a switch on stereotypical generational behavior, its the dad, DavidNettleton who mischievously bounces S4/i lenses o the oor to provelens resilience. As weve said beore, although the lens survived, youshould not attempt. May void warranty.

How to Build a Lens

History Review


4/8

June 2007

he sae-house is north, says the driver. We have driven through ogand rain to a row house on the outskirts o Leicester. he driver knocksthree times. It could have been a scene rom John le Carr. No, more J.K. Rowling. Te street looked like Privet Drive in Little Whinging, withwizards lurking in the shadows, streetlights ickering.

Were in Mountsorrel, a village on the outskirts o Leicester, wherewizards and designers stay when working at the Cooke actory just downthe road. Lots o late night arrivals and departures have inspired imagi-native neighbors weaned on Smiley and 007 to call it the Sae-House.Its real name is Te Gatehouse. Guy Genin is the G o ZGC, Inc.Guy is on one o his requent trips to the actory. Guy services most othe Cooke lenses in the US at ZGC in New Jersey, and was my graciousactory, tour and restaurant guide or three days.

Lens theory 101 in one sentence: glass elements are moved toward oraway rom the image plane to achieve ocus.

Lenses are made o groups o polished glass diskscalled elements.Each element is ground according to exact specications: or curvature,spacing, arrangement, thickness and diameter.

o move the glass, metal carriers hold the elements and move them withgreat precision, smoothly and in exact alignment with the ocus scalesengraved on the outer barrel. Oh yes, and they must endure the abuse olie in production, extremes in temperature, being dropped, lef out inthe rain, and all kinds o other horrors that make any designer cringe.

A amous British industrialist said, I you cant measure it, you cantmake it. So, there is as much measuring as grinding, polishing andtting at Cooke. Oh yes, and coating. All glass suraces reect 4% o thelight passing through. I your lens had 22 elements, with 44 suraces, notmuch light would get through.

Cooke lens coatings reduce reections to .1%. A brew o silicon andtitanium, hardened with magnesium uoride coats each element. It is1 nanometer thick, which is 1 millionth o a millimeter. Your whiskerswill grow longer than that in 1 second afer the swipe o your razor.

Te mechanical part o the optical-mechanical-electronic trinity is anarray o precision machined barrels that move the internal elements inexact harmony with scribed ocus and aperture marks on the outside.

Recently, with the introduction o smart lens technology, electronicshave been added to the mix in the orm o the /i-Lens system. Sensorsprovide continuous updates on distance, -stop, and ocal length.

Cooke, contd


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June 2007

Te glass is selected and precisely pre-edged to an exact diameter on a CNCmachine. Tis diameter will be held through the process until nal edging isdone.

Te Computer Numerically Controlled machine grinds both sides, estab-lishes the optical center, curves and thickness. CNC machines are also usedto make aspheric lens elements, which well see a little later.

With a CNC machine, you can grind one element at a time in about 15

minutes. Its been compared to a microwave that can heat up your dinnerone plate at a time.

When they invite more cinematographers to dinner and need more din-ner plates, they use D-type polishers, designed and built in 1913 and stillcapable o precisely polishing 120 elements on 6 spindles in 8 hours.

Heres Dave Stevens, managing director (lef), to whom we are most grate-ul or his encyclopedic knowledge o acts and gures, history and science,and above all, nanometers per second tonsorial growth rates.

Te glass elements are held onto the base o the polisher with a sticky, blackpitch. Te top cone randomly orbits the glass, slowly polishing with a

serium oxide sludge.

Polish is periodicallyadded with a brush.

Tere are numer-ous shapes on handor polishing theelements that go intoCooke lenses. Herewe see many ele-ments being workedon at the same time.

Te shapes denecurvature o thelenses, as dened bythe mathematicalormalae that havebeen established.

Despite the speed oCNC polishing andgrinding, perhapsit is the traditionalhandmade crafs-

manship o theD-type polishingthat gives Cookelenses their uniquecharacteristics, whichare ofen describedin terms usually re-served or tasting newines: roundness,ullness, smooth anddelicate all-o.

Cooke, contd


6/8

June 2007

Over 5000 test glassgauges are available toenable almost any sizeelement to be made atthe designers discre-tion.

Mick Maher (right),one o the skilledpolishers, smoothingthe elements prior topolishing.

Spherical lenses have consistentcurves. o make an aspherical lenselement, imagine slicing a volley-ball in hal, and glueing it onto thetop o a Frisbeebut on a muchsmaller scale. Because the outeredge o the lens has a dierent ge-ometry, the element can be smallerand lighter, with less edge distor-

tion. Te Cooke CXX 15-40mmzoom and SK4 6mm use asphericelements.

Afer coating, BrianCrow (right) does thenal grinding o theedges and remeasuring.He grinds the diametersslightly undersized romthe nal tolerances toaccommodate the next

step: edge blacking.

Its time to put all thepieces and parts together.Barrie Billington (lef) isthe assembly manager,shown here in the assemblyroom.

Tey call it the ttingroom, a term that re-minded me o bespoke suitmakers and custom shirttters in Jermyn Street.

Cooke, contd

Te edges o each element aresprayed with a specially ormulatedblack epoxy paint.

I the edges were lef clear, lightwould bounce around between theelements, the metal housing andcreate reections, are and ghost-ing. Spraying with the airbrush isa very delicate process, done withgreat care.


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June 2007

Once the lens is assembled,like a Russian doll, it is takenapart againtotally strippeddown.

Te next steps involve care-ully cleaning all the elementsand parts again.

All the individual parts o eachlens are kept together untilreassembled.

Tere are between 10 to 14elements and 60 mechanicalparts in an average Cooke S4/i lens.

Te lens barrels are machinedrom aluminum tubes andthen anodized.

Element assemblies ride ontwo sets o precision bearingsinside the barrel, preciselyguided by the amous Cookecams (lef), which are essen-tially channels or reewayon-ramps in which the camollowers (right) travel.

Te cam and cam-ollower

present much less rictionthan threaded lens barrels.Te threads require grease toprovide smoothness.

Cooke S4/i lenses worksmoothly in temperaturesrom -25 C to 55 C.

Te cam-ollower is made oDelrin, which is very durableand does not need lubrication.

Next, add an iris, (lef andright).

Cooke, contd

Apprentice Simone Ryan (lef)selects a ront element mask.

Tis one is tted to a 35mmormat S4 lens when shootingin Super16 ormat to preventinternal barrel are by block-ing extraneous light rom thewider, unused diameter.


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June 2007

Te optical elements are washed, andthe entire lens is careully put back to-gether in a totally dust-ree clean room.

I asked Adam Woolley (right) whats thebest cleaner or lens elements when theyare smudged.

He likes acetone on a cotton ball.

Apparently the epoxy edge blackingand the coatings are hard enough towithstand acetone. I cannot vouch orany other lenses until I check with theirmanuacturers.

Focus is checked or each increment ocritical ocus.

Focus scales are then engraved accordingto the computer data entered or eachlens.

/i lenses are checked by computerwithout readouts o all inormationand metadata that will be used duringproduction.

In 1667, Francis Smethwick ground therst high-quality aspheric lenses andpresented them to the Royal Society inLondondocumented in his paper AnAccount o the Invention o GrindingOptick and Burning-Glasses, o a Figure

Not-Spherical, Produced beore theRoyal Society.

340 years later, the crafsmen andwomen at Cooke Optics are carrying onthe tradition o ne optics.

Tere. Tat wasnt so dicult to build,was it? Minor assembly required.

Heres a nished Cooke S4/i 150mmlens, ready to go out into the real worldo production.

Cooke, contd

2007 Film and Digital Times, Inc

F&D Times Cooke Tour

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