Why is multi-coated filter needed if lens already has multi-coating?

Started Jul 11, 2010 | Discussions thread
Legion5
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Re: Why is multi-coated filter needed if lens already has multi-coating?
In reply to steamboatscott, Jul 11, 2010

steamboatscott wrote:

I'm looking for a filter to put on my EF-S 17-55 f/2.8 IS, in addition to the hood. Probably won't use the filter all the time, but in those occasions that I'm in above average dust or possibly some moisture, it will give me a sense of protection (note I also have insurance on the lens, so worst case, I'm always covered).

I'm debating between the Nikon NC 77mm filter (which is multi-coated), the B+W UV 77mm (around $50 for non multi-coated) and the B+W Clear MRC 77mm (around $88 for multi-coated). I've read the suggestions throughout here and other sources about the benefits of multi-coating in filters for preventing reflection/flare. However, if my lens glass already has the multi-coating, is that sufficient to not really need the multi-coating on the filter?

I really like the Nikon NC for the price ($50 with multi-coating), but those B+W brass rings sure do thread better.

I understand the B+W MRC Clear is only about $38 more in price, but either way, I'd like to get educated on the necessity of multi-coating on a filter when the lens already includes the coating.

Never buy a filter that isn't multi-coated, it will severely degrade your image quality. Multicoating is necessary to make the glass more transparent, and glass that isn't multicoated usually transmits 5-10% less light. To put that into perspective, 5% is generally blatantly visible by even the casual observer in a side by side comparison. Generally the best uncoated filter is worse than the worst multicoated filter.

From a flare perspective each piece of glass in your lens is a light source when in a flare situation. Imagine each piece of glass as a seperate flashlight shining on a wall. Multicoating is like adding a dark tinted filter over each of those flashlights thereby darken them so they don't shine on the wall as brightly. What you're expecting is the tinted filters on the flashlights you already have to also darken a new flashlight you're adding (the glass of the new filter), that would be ridiculous, and multicoating doesn't imbue new pieces of glass with the benefits of multicoating.

Nikon has never published their transmission results for their filters, which makes buying them about as shady as buying a DSLR from a guy in an alleyway. It would be a horrible decision to go with Nikon simply because you don't know what you're getting. I would not be impossible that Nikon found the cheapest UV filter manufacturer and rebranded their products.

If you want the best UV filters get B+W multicoated filters (any kind). If you want ones that are nearly as good, get Hoya Multicoated UV filters (any kind). I only use UV filters because they make lenses easier to clean and keep clean, but I'm also one of the most fanatical people when it comes to image quality, so I've heavily researched UV filters and their effects on a lens.

If it matters B+W uv filters are easier to clean than Hoya ones, and are made of brass which is a soft metal so they won't get stuck in hot or cold climates or if sand gets in the thread.

Clear and UV filters have nearly identical performance from the top manufacturers, in terms of image degradation (which is to say almost none), but UV filters offer additional features of blocking some atmospheric haze, which makes them better considering they are identical in price last I checked.

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