Uncoated Lenses: Just As Good?

[kelly_flanigan1]

The black trim Kodak Ektar 127mm F4.7 on a black looking ww2 trim 4x5 speed graphic IS coated; with NO "L" marking and is a date code of EO2113; a 1946 Camerosity code. <BR><BR>A friends 1945 black trim 127mm Ektar IS coated with no L marking .<BR><BR> A pre war 3x4 speed has an unloaded 127mm ektar; with a 1941 date code is NOT coated. <BR><BR>The Ektra here has a EY27X code on its 50mm F1.9 Ektar; for a 1940 date; on a 24XX camera body IS Coated. <BR><BR>The Kodak Bantum Special here has a nice 45mm F2 Ektar; with a EC34XX serial from 1941 IS coated. <BR><BR>The Kodak Vigilant 620 here from 1946 has a coated lens.<BR><BR>The many 178mm F2.5 Aero Ektars I have owned or used have ALL been coated; with 1943 thru 1945 date codes; with no L marking.<BR><BR><BR><BR>The last time I worked in a OCLI clean room it was in Santa Rosa in the the 1980's; aligning an optical bench. The brewery in the 1930's was once a primitive ice rink; pre Snoopy. A later real ice rink opened in 1961; the Schulz rink in 1969.<BR><BR>The pre ww2 Kodak books and post ones mention lens flare. In studio conditions the effects of an coated lens versus an uncoated lens are way less than the harsh uncontrolled outdoors. The ancient rochester state street books have one developing more/longer with an uncoated lens; or a coated lens under harsh conditions. The transfer function on at the film gate has a shallower slope with flare. The shadows tend to fill in; the signal to noise ratio less. The later 1960's and 1970's Kodak F-5 books further went into trials with coated versus uncoated lenses; studio versus non studio conditions; diffusion versus condenser enlarger; or even a point light source one.<BR><BR>With a decent high contast scene and studio conditions the uncoated versus coated change is WAY less than a harsh amateur scene on the beach. Thus whether a lens coating makes alot of difference will vary with what and how a cine/photographer shoots. It radically also depends on the lighting ; whether a lens hood is used; or if unwanted non scene light can be blocked with barn doors on lights or lens. <BR><BR>Worrying about coatings versus non needs to be taken with the job one does. Waxing a race car helps the top end speed more on a race car versus a riding mower. The non thinker will always state that coatings helps alot; or waxing too.:)

[david_m]

"its main advantage is in controling flair."

 

-In that case, I definitely don't want to use it.

[profhlynnjones]

To Dan,

 

The woman who did the research working on her PhD owned all the rights and George at B&J agreed to that in exchange for jointly working with the process. Kodak was doing artificial lens coating in about 1931 (I don't remember it since I was borne in 1931). It is probable that wollensak was investigating coating at about the same time as Kodak. I don't think that any of them patented these processes although they copyrighted the names that they used for their coatings. The earliest I remember seeing coating from the Germans was in about 1937, I have a Kodak Retina with a Schneider f 2.0 from 1937 and it is a heck of a lens.

 

OCLI patented their 7 coat process in the 1960's. There were several 2 coat processes in the astronomy business in the late 60's and I'm aware of some of those 2 step systems in the late 50's, but nobody seemed to talk about that.

 

You may be right Arjun, but maybe not, Kleenex is my favorite for that purpose, and destroying natural coating is nearly always a friction problem rather than a solvent problem, but who knows? I have actually shot with some uncoated new lenses and the results were not a happy event for me.

 

Lynn

[brian_wallen]

From Lenses in Photography, Rudolf Kingslake, Director of Optical Design, Eastman Kodak Company, Rochester, 1951,

p. 109-10.

 

...The possibility of this [reducing the surface reflectivity of glass] was recognized by H. Dennis Taylor in

1896 when he noticed that some old lenses having dark tarnished surfaces transmitted more light than a new lens

of the same kind, the reduction of surface reflectivity due to the tarnish actually causing an increase in the

lens transmittance. Subsequent attempts to produce this kind of tarnish artificially were irregular and

generally unsatisfactory, and the procedure was never attempted on a commercial scale. In 1936, Professor John

Strong* of California suggested that surface reflection could be reduced by depositing a thin layer of some

low-index material upon the surfaces of a lens. The material first proposed was calcium fluoride and the

deposition was done in a high vacuum by direct sublimation of the heated crystalline powder. As the thin layer

is gradually deposited in the vacuum chamber, it passes through the same range of colors that are seen on the

surface of iron when it is strongly heated, namely, light straw, darker straw, brown, magenta, blue, and finally

deep purple. The correct point to stop the deposition for normal photographic purposes is somewhere in the brown

stage.

 

...

 

Commercial low-reflection coatings of this kind were first offered for sale in December 1938, and since that time

great strides have been made in improving the process. Calcium fluoride is very effective in reducing

reflection, but it yields a soft layer which is easily rubbed off. Consequently it was early replaced by other

fluorides, which together with improvements in the vacuum technique, have made possible coatings which are now as

hard and durable as the glass itself. The photographer is cautioned, however, against the use of

silicone-treated cloths as the silicone material changes the characteristics of a coated lens.

 

_______________

 

* J. Strong, "On a method of decreasing the reflection from non-metallic substances." Journ. Opt. Soc. Amer. 26,

73-74 (1936).

 

---------------------------------------------

 

Kingslake goes on to explain the effects that coating produces in highlight and shadow areas and in establishing

film speed indexes.

 

In his 1989 title, A History of the Photographic Lens, Kingslake notes that in 1936 A. Smakula of Zeiss invented

the process of vacuum deposition on glass elements. I don't have a private copy of this, so I can provide a page

reference.

 

In a 1998 post, Marc Small summarizes early Zeiss coatings:

 

Alexander Smakula combined the two elements necessary for successful lens coatings, fluoride compounds and

vacuum-depositing techniques. He began this while completing his doctorate in an internship at the small German

optical works of Pohl; afterward, he was hired by Zeiss, where he completed the process in 1935. Zeiss began the

commercial production of coated lenses in 1937.