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ed nygard

Optical coating for ports

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Seacam offers as a recommended option optical coating (presumably on the interior surface) of the port lens. Any one have any experience, test data, examples or knowledge of the practical utility of coated vs noncoated port lenses for underwater photography? Is there a discernable difference in contrast, saturation, reduced flare or other benefit to justify the cost?

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Ed and I have been corresponding personally, but as his question is a good one, I went to the source, Harald Hordosch of Seacam Austria. We agreed I should do some side-by-side testing to conclusively answer this question.

 

Sorry ... I have never owned 2 superdomes, one coated and one not-coated, and they never stay here for more than a day before going out to customers. So, I haven't been able to do any scientific evaluation. But, for anyone interested, here is the content of our last e-mail:

 

<<My post to Ed: Ed - I am very much looking forward to doing some testing. Thanks for bringing it up.

 

For whatever it is worth, I have been getting internal reflections with my superdome and Canon 17-40/16-35mm lens. If the coated superdome cures that, and if my time is worth a dollar-an-hour in Photoshop, the optical coating will pay for itself in a month :-)

 

Personally, if it was me, I'd go for it on the dome ports anyway. But I say that only because you probably have to make a decision soon. If you have a month or so, wait for my coated superdome to arrive and I'll do some conclusive testing.

 

Thanks.

 

Steve

 

<<Harald's post to me:

Subj: AW: optical coating for ports

Date: Tuesday, May 3, 2005 3:13:00 PM

From: office@seacam.com

To: Frinkphoto@aol.com

 

Dear Steven,

 

You are right and we should get some test pictures immediately – I will send you a coated SD ASAP. Here is information about optical coating:

 

 

 

Coatings on lens surfaces reduce light loss and glare due to reflection for a brighter, higher-contrast image. SEACAM optics are coated with a microscopic film of magnesium fluoride. Coatings lead to better light transmission. SEACAM ports can be coated on request – inside the port glass.

 

 

 

“Optical coating - highest brilliance

We cannot imagine optical elements without high-quality coating which definitely contributes to reflex-free SEACAM front glasses and their unique contrast. For that reason all front glasses can be coated upon request. The perfect correction and proper choice of the front glass allow doing almost without close up lenses. Thus there will be no optical impairment of your high-quality lenses. For lenses which require a dioptre for optical reasons we offer it with optical coating.†Seacam web site

 

 

 

First - Optical coating is the most important part on all optical elements. Every lens is done with a high grade of optical coating, if they would not have it you could even not look through. Light passing a glass element is loosing 3-5% on each side – high sophisticated optical lenses have 6-8 different lenses – you could calculate how much light will stay.

 

Second – optical coating will prevent optical systems from reflections – I am sure you have seen the rings, if you shoot into the sun – on cheap lenses – this causes a bad quality of glass and optical coating!

 

Third – optical coating will improve the brilliance of your pictures – this is told to us from many customers using SEACAM ports which are optical coated.

 

 

TYPES OF COATING

Coated - A single layer on at least one lens.

Fully-Coated - A single layer on all air-to-glass surfaces.

Multi-Coated - Multiple layers on at least one lens and all surfaces are coated at least once.

Fully Multi-Coated - Multiple layers on all air-to-glass surfaces.

 

OPTICAL COATING TYPES

Coated: Lens surfaces are coated to improve light transmission capability.

Fully Coated: All air-to-glass surfaces are coated.

Multi-Coated: One or more surfaces or lenses have been coated with multiple films and all surfaces are coated at least once.

Fully Multi-Coated: All air-to glass surfaces have multiple films.

Magenta Coating: Reduced reflection, fully coated optics throughout.

HDCâ„¢ High Definition Coating: Heat-treated, multi-coated objective and ocular lenses. Fully coated throughout.

Rubicon® Coated: This coating consists of 14 layers of multi-coating on the objective lenses and is characterized by ruby-red colouring on the objectives. It provides excellent bright daylight and glare conditions viewing because it filters out red light.

SuperConâ„¢: Heat-treated, fully multi-coated optics throughout.

 

Best

 

Harald

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I had optical coating done when it wasn't too expensive, which means that my superdome isn't coated, i don't think.

 

I found that I have internal reflections using the superdome when the lens sticks out too far into the dome port. Douglas Seifert says he's using the recommended extension for his 17-40, and his lens sticks out more than my 16-35 does. i *think* I'm using the recommended extension, but i can't be certain anymore. all i know is that with my extension, i don't need to use an internal diopter, and can focus to around 6" from the superdome. :)

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I had optical coating done when it wasn't too expensive, which means that my superdome isn't coated, i don't think.

 

I found that I have internal reflections using the superdome when the lens sticks out too far into the dome port.  Douglas Seifert says he's using the recommended extension for his 17-40, and his lens sticks out more than my 16-35 does. i *think* I'm using the recommended extension, but i can't be certain anymore.  all i know is that with my extension, i don't need to use an internal diopter, and can focus to around 6" from the superdome. :)

 

Eric - You are using the right extension I'm certain ... a PVL35 with your superdome for 17-40. I found the same using a 16-35.

 

I really don't think that's the issue with the internal reflections. The paint they use on the front of Canon lenses is just too damn shiny. I tried painting it but could never get flat black enough. Now I've heard the dulling paint they use for gunsights might do the trick. But first, I ordered a collapsible rubber lens hood from B&H on Walt Sterns' recommendation (B+W brand). Walt says this does the trick for him.

 

Truthfully, I think the multi-coating is more for light passing in rather than that bouncing around inside, reflecting those metal parts of those zoom lenses. Bill Harrigan and I were talking about this today, and he noticed it was only verticals affected.

 

I think I'm pretty close to getting this fixed, either by means of this filter or a real matte black paint. I'll report back on what the final conclusion might be.

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Thanks, Steve.

 

I've never had reflections in any of my images, except when the lens stuck out too far into the dome (I have no idea what I was trying at the time...).

 

Perhaps it was coincidental! When I use extensions, the lens *barely* sticks out into the dome area. When I get settled here at home, I'll go measure the one I've been using. Maybe I've been wrong this whole time! :)

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I’ve never compared side by side. But reducing reflections is a dedicated feature of the coating. Reflections within big domes can always occur to be an issue even if the lens doesn’t protrude far into the dome. Beside bright lens front letters - reflections can be caused by the aperture blades (correct English word?) and the sun itself within the dome glass and so on.

 

Someone who has compared side by side over here states that the coated Superdome is noticeably less prone to reflections.

 

Theoretically coating enhances light pass thru, contrast, colours, …. But I don’t know how much this is noticeable in real world.

 

Before ordering my concern was how fast this coating is worn-out. But this concern was not valid as the coating is applied to the inside of the dome glass.

 

Having that said my Seacam gear is declared to leave soon :)

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