# Coated vs uncoated lens?



## minicoop1985 (Apr 29, 2016)

Just a pretty general question here. Has anyone shot color film in a camera with an uncoated lens? What were the results like? I'm debating on which lens to use on my little Robot once the parts arrive (the coated lens has some minor fungus, but not enough to affect IQ).


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## SoulfulRecover (Apr 29, 2016)

an uncoated lens with have a lot more flare issues so a lens hood would help a lot. The image wont have as much contrast either and some people claim that in daylight, the image has cool tones.


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## minicoop1985 (Apr 29, 2016)

Well, I can test the two of them side by side to test that theory (the cool tones). I have a feeling I'll end up using the uncoated white triangle Schneider more than the red triangle Schneider since the white's in better shape.


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## limr (Apr 29, 2016)

minicoop1985 said:


> Just a pretty general question here. Has anyone shot color film in a camera with an uncoated lens? What were the results like? I'm debating on which lens to use on my little Robot once the parts arrive (the coated lens has some minor fungus, but not enough to affect IQ).



Buzz shoots Ektar in his uncoated Rolleiflex and it's gorgeous.
The Count Trossi Mercedes
3Oct2014-3-11_Modified_Border
3Nov2013-1-07_Modified_Border


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## minicoop1985 (Apr 30, 2016)

Maybe I'll just stick with the white triangle lens for now. Been using it most of this roll.


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## petrochemist (May 2, 2016)

Uncoated lenses reflect 4% at each air glass surface. A single coating can reduce that about five to ten fold, multicoating is better still.
Most lenses will have at least 6 air/glass surfaces, modern ones usually have more (even many more).
The cumulative effect is significant, 6 uncoated surfaces is enough to reduce the image forming light to little over 3/4 of what reaches the lens.


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## compur (May 2, 2016)

Yeah, uncoated lenses are worthless. Especially Schneiders. Nobody ever took a decent photo before lens coating was invented. They're only good as dog toys and drain plugs. I'll take yours off your hands. I have a doberman that likes to chew on them.


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## john.margetts (May 3, 2016)

minicoop1985 said:


> Just a pretty general question here. Has anyone shot color film in a camera with an uncoated lens? What were the results like? I'm debating on which lens to use on my little Robot once the parts arrive (the coated lens has some minor fungus, but not enough to affect IQ).


I have shot colour film with an uncoated, not colour corrected lens with good results. Lens:Voigtlander Skopar. Camera:Voigtlander Vito I (1945)


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## minicoop1985 (May 3, 2016)

compur said:


> Yeah, uncoated lenses are worthless. Especially Schneiders. Nobody ever took a decent photo before lens coating was invented. They're only good as dog toys and drain plugs. I'll take yours off your hands. I have a doberman that likes to chew on them.



lol.


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## cgw (May 3, 2016)

Intelligently shot(an obvious challenge for some), they're fine. A lens hood, flare-excluding light placement, and a sense of scene contrast cut the odds for problems. Things like fungus, element separation and haze are way bigger worries with older glass.


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## MartinCrabtree (May 3, 2016)

They tend to work better with film than digital. CA shows itself more readily with a sensor from the RGB all being on the same level. Film has layers which accommodates the differing wavelengths to some extent. Shoot away and see what you get. Of course like any other unknown avoid using it on critical need work. Have fun you may be surprised and pleased at what you get.


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## Watchful (May 3, 2016)

Other factors will have a far greater impact on the image captured than if the lens has a coating or not under most conditions, the exception being strong direct back-lighting, or solar illumination directly hitting across the lens surface, both of which can be easily avoided.
Use what you like and set up your shots according to what you use.


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## Watchful (May 3, 2016)

john.margetts said:


> minicoop1985 said:
> 
> 
> > Just a pretty general question here. Has anyone shot color film in a camera with an uncoated lens? What were the results like? I'm debating on which lens to use on my little Robot once the parts arrive (the coated lens has some minor fungus, but not enough to affect IQ).
> ...


This is not the best example of a good result imo.


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## john.margetts (May 3, 2016)

Watchful said:


> john.margetts said:
> 
> 
> > minicoop1985 said:
> ...


Not a brilliant picture artistically - but no flare (the avoidance of which is the main point of coating lenses) and no apparent colour aberration from an old non-colour-corrected lens. Same camera/lens:


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## Tim Tucker (May 6, 2016)

petrochemist said:


> Uncoated lenses reflect 4% at each air glass surface. A single coating can reduce that about five to ten fold, multicoating is better still.
> Most lenses will have at least 6 air/glass surfaces, modern ones usually have more (even many more).
> The cumulative effect is significant, 6 uncoated surfaces is enough to reduce the image forming light to little over 3/4 of what reaches the lens.



A single surface or density change _will reflect 4% of the light_. But multiple surfaces are NOT a cumulative total. Multiple surfaces will reflect between 0-16%. I know this sounds odd and counter intuitive but the maths that predicts it was worked out by Richard Feynman and it's been tested and found to be correct, in fact modern lens coatings are designed with it. The total of the reflected light through modern lenses can be less than 4%, and in uncoated lenses it can be as much as 16% (not including scratches ).



minicoop1985 said:


> Just a pretty general question here. Has anyone shot color film in a camera with an uncoated lens? What were the results like?



I use a Ziess Tessar circa 1910 on my half plate at times. The lens is incredibly susceptible to flare. You have to be very careful not to let any stray light hit the surface of the glass, and I mean really careful. It's a little more than just a lens hood, it has to be in shadow or you'll have problems. I've only ever shot B&W with it and generally with an orange or yellow filter.

The flare though does give it one remarkable property. The level of flare when you're being _really_ careful is just around the threshold sensitivity of 80ASA film. What this effectively does is pre-sensitise the film meaning any further light that hits the film has enough energy to cause a reaction, and this gives it an ability to record a remarkable amount of shadow detail. For instance:


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## petrochemist (May 6, 2016)

Tim Tucker said:


> A single surface or density change _will reflect 4% of the light_. But multiple surfaces are NOT a cumulative total. Multiple surfaces will reflect between 0-16%. I know this sounds odd and counter intuitive but the maths that predicts it was worked out by Richard Feynman and it's been tested and found to be correct, in fact modern lens coatings are designed with it. The total of the reflected light through modern lenses can be less than 4%, and in uncoated lenses it can be as much as 16% (not including scratches ).



The reflection at a surface depends on the change in refractive index of the two mediums. Anti reflective coatings are made with a carefully tuned refractive index (between that of the the materials either side) and with precisely controlled thickness. This ensures the light reflected from the front surface of the coating destructively interferes with light reflected from the rear surface cancelling out both reflections. Modern multi coatings use a series of layers so that they can be fine tuned to the different wavelengths that might be significant. If you try infra red photography you will find modern coatings generally do very little to reduce reflections of infra red wavelengths.


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## Tim Tucker (May 6, 2016)

petrochemist said:


> Tim Tucker said:
> 
> 
> > A single surface or density change _will reflect 4% of the light_. But multiple surfaces are NOT a cumulative total. Multiple surfaces will reflect between 0-16%. I know this sounds odd and counter intuitive but the maths that predicts it was worked out by Richard Feynman and it's been tested and found to be correct, in fact modern lens coatings are designed with it. The total of the reflected light through modern lenses can be less than 4%, and in uncoated lenses it can be as much as 16% (not including scratches ).
> ...



Exactly, well that's how the maths works.  For light hitting a single surface (of glass) straight on the reflection is always the same, around 4%. Even with uncoated glass the reflection off the rear effectively "interferes" with the reflection off the front, (it is not actually the surface of the glass but the glass itself and nobody  can really explain why). When light hits the second glass lens surface this does not "start again" and become a cumulative total but "interferes with the light reflecting off the first lens surface". 

It's worth clarifying this as there's a lot of internet nonsense about modern multi-coated multi-element zoom lenses. I entirely agree with your observations on IR.


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## petrochemist (May 7, 2016)

The reflections from both surfaces of uncoated glass  will indeed interfere, but it won't be purely destructive interference. In some places the amplitudes will add to increase intensity.

I have studied the depth of penetration on total internal reflection somewhat for spectroscopy use. I don't remember the formula but I remember it related to both wavelength and refractive index (significantly complicating quantitative work using ATR rather than transmission cells) I suspect the physics of it will be similar for other surface reflections at less than the critical angle. I'm glad to hear I'm not alone in not understanding why it happens!


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## jvansanten (Jun 17, 2019)

petrochemist said:


> The reflections from both surfaces of uncoated glass  will indeed interfere, but it won't be purely destructive interference. In some places the amplitudes will add to increase intensity.
> 
> I have studied the depth of penetration on total internal reflection somewhat for spectroscopy use. I don't remember the formula but I remember it related to both wavelength and refractive index (significantly complicating quantitative work using ATR rather than transmission cells) I suspect the physics of it will be similar for other surface reflections at less than the critical angle. I'm glad to hear I'm not alone in not understanding why it happens!


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## IanG (Jun 19, 2019)

petrochemist said:


> The reflections from both surfaces of uncoated glass  will indeed interfere, but it won't be purely destructive interference. In some places the amplitudes will add to increase intensity.
> 
> I have studied the depth of penetration on total internal reflection somewhat for spectroscopy use. I don't remember the formula but I remember it related to both wavelength and refractive index (significantly complicating quantitative work using ATR rather than transmission cells) I suspect the physics of it will be similar for other surface reflections at less than the critical angle. I'm glad to hear I'm not alone in not understanding why it happens!



As someone else revived this thread 

About 2 or 3 years ago I tested quite a few uncoated lenses,  they results were quite predictable.

I started with a 1913 110mm f6.8 Dagor (CP Goerz Berlin) this was the highest contrast close to a modern  MC lens as with only 2 internal air glass surfaces, next was a 165mm f5.3 CZJ Tessar an uncommon aperture, with 4 internal air glass surfaces there was a noticeable loss of contrast, next was an Ihagee-Goerz 135mm f6.8 dialyte lens with 6 internal air glass surfaces there was a significant drop in contrast making it a challenging lens to use.  Finally a Meyer Weitwinkler WA lens a double Gauss design like a dialyte 6 internal air glass surfaces this had the lowest contrast of all.  I have examples but I'm not in the UK and don't have access to them at the moment.

For my main work I only use coated lenses. they include a two Angulons a 65mm & 120mm, a few Super Angulons 65mm, 75mm (f8 & f5.6), 90mm f5.6, and a 165mm f8, plus a CZJ 150mm T coated Tessar, and some Xenars plus a Tele-Xenar.  There's no difference between these and my Multi Coated LF lenses.

Ian


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