Single or Multi coated??
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HoppyUK
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Looking to purchase a B+W 110 ND Filter, (Try my hand at long exposure),
Had a look on Amazon and found that there are more than one,
so could anyone tell me the difference between Single and Multi coated
Many thanks. Pete.
One is single coated, and the other is multi-coated...
Basically, uncoated glass reflects a small but significant amount from the surface. This isn't good, but is even worse it then bounces around inside the lens. It reduces contrast and promotes flare.
Coating on the rear surface is especially beneficial as it reduces ghosting. This is light reflected off the shiny surface of the sensor, then back again from the rear of the filter, to form a mirror ghost image. You'll notice it with street scenes at nights, sunsets, that kind of thing.
Coating reduces this a lot, and multi-coating reduces it a bit more.
The MC B+W 10-stopper is the best there is, and I think I've tested them all
Cuchulainn
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Hoppy is right, though there is one other thing to consider for single versus multi coated lenses. Typically a single coated optic will have very low reflectivity at one design wavelength but won't be quite as good at other wavelengths. As an example, here is a typical set of reflection curves for MgF2 from an optics supplier. This is a cheap and durable single coating. AAs you can see, whether the optic component is at right angles to the light or at 45 degrees to it, there is an improvement in the amount of light being reflected, but it's not uniformly low. Multi coatings can be a bit cleverer and have a lower overall reflectivity over a wider range of wavelengths or input angles.
HoppyUK
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Fair comment. The kind of situations in which you're most likely to use a 10-stop ND are unlikely to include the very bright light sources that cause most problems with filters in general. With the possible exception of sunsets I guess.
The Lee Big Stopper is uncoated, and that's very highly regarded. So is the Haida ten-stops, and that's a bargain at £40. Heliopan is v good. And Hoya too, LightCraftWorshop likewise - both nearer 8-stops.
They all have a slight colour cast of some sort, but easily corrected with a custom white balance or in post processing. The only one I've had any difficulty with is the HiTech Pro Stop that suffers from IR interference that can't be corrected.