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Multi-Coated Camera Filters, are they worth it? 
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Is your current camera filter, Multi-Coated or even Mono-Coated?

Here is a very simple way to check.
Look at the reflection of a lamplight bulb, at an angle, on the surface of the camera filters glass (UV's or clears are the best to use). Camera filters that have optical coatings, multi or mono-coated, will reflect white light, when viewed from an angle, at a color tint, slightly different than the white lamp.

Multi-coated camera filters will reflect the reflected lamps image in many different colors (usually magenta and green tones), depending on the number and kind of optical coatings applied to the surface of the filter glass, just like most camera lenses. Mono-coated (single coated) camera filters will show a color tint change, but the color tint is harder to see. Non-coated camera filters will show no color tint change, of the bulb. To compare the reflections, use glass that is known not to be coated. use regular window glass or glass from a simple photo frame. 

Don't be surprised if your camera filters do not have any coatings at all. Many well known camera filter brands offer filters without optical coatings.

2012 update, 2filter's tech people are now seeing all over the web, just like 2filter did 25 years ago, brands and camera filter products being offered in 2012 from many new countries as multicoated that are Not Coated. The packages say they are but the camera filters inside the boxes still are not. some selling games never change

Stop defeating the fine coatings on your Dslr lenses with camera filters without any optical coatings. MULTI-COATED FILTERS are available from all our camera filter companies. You will see a difference in your image files, especially if you shoot without a lens hood outdoors or with a wide-angle zoom with a shallow hood.

Multi-Coated Filter Cross Section
The above image was 1st created in 1989 and is property of 2filter.com

Today's lenses from all the camera companies -- wide angle zooms or telephoto zooms lenses are all multi-coated. Multi-coating helps reduce most surface reflections. 2filter's tech people feel this is an important function, allowing maximum light transmission. However, this multi-coat benefit is only secondary to the reduction of flare (reflections).

The problem of natural lens flare is encountered from any stray light entering the optical path from angles not necessary to capture the required image (in 1989 on film). Lens flare is most noticed when you are taking images with strong back light situations, example Sunsets, strong light colors, studio portraits, fashion etc. Using lens hoods as deep as possible for the working focal length in use is a big step in reducing the light flare problem. Today's zooms have such a wide range. The hoods supplied with lenses are usually very shallow - to cover 28 to ??? (200mm focal length).

The reflections of light happen at every air space between lens elements and filters. Internal lens reflections are usually at an extreme minimum because the light becomes focused as it passes through the lens elements. 

FYI, The rear optical coating of camera filters (the glass that faces the camera lens) is the most critical surface to be coated. If the camera filter's rear surface is multi-coated, it will reflect the minimum amount of light back to the first element in the lenses group.

Using uncoated filters this flare can happen even without the sun in the picture
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