lawrence
Veteran
I have what superficially appear to be two Hoya UV(0) filters (I don't have the original filter cases). Looking at the filter rims gives the same info in exactly the same lettering: 'Hoya 49mm UV(0) Japan'. The spacing and colouring of the letters is identical. However, when I reflect daylight from a window onto the front surfaces, one filter reflects as quite strong purple/blue and the other as a light amber, so I guess one of these filters is fake. My question is, which one?
Highway 61
Revisited
What you have are basic Hoya UV(0) filters manufactured at different times. Both are single coated. The reflected color of the single coating layer changed over the years. The amber colored filter is probably the oldest of the two. No fakery plot here.
lawrence
Veteran
Thanks for the info. I plan to use one the filters for monochrome (film) and thought that the amber one, which does look older, might be more suitable as it would be closer to a very light yellow filter. Do you have any thoughts on this?
AFenvy
Established
I don’t think the reflected color from the coating on a filter could ever be detected in an image. I’d even argue that the difference an actual light yellow tinted filter makes on a B&W image is so negligible you’d have to do a scientific comparison to see it. For B&W I have to use an orange filter to really see an effect.
lawrence
Veteran
I have to disagree, the effect of a medium yellow filter, such as Nikon Y48, is noticeable and even a Y44 light yellow filter has an effect. I'm sure that Nikon wouldn't bother to make them if this were not the case.
Dwig
Well-known
The color seen in reflections from the surface of a coated filter has absolutely nothing to do with the transmitted spectrum and thus will have no impact on the image. It is the result of interference between the two reflections, one from the top surface of the coating and one from the coating-to-glass boundary. The color seen is a factor of the coating's thickness. With multi-coated filters you also get additional reflections from each of the layer-to-layer boundaries. You can Google "Newton's Rings" for more information.
lawrence
Veteran
Thanks, this makes sense as otherwise the difference between the two Hoya filters would mean that they couldn't both be UV(0), which was what I had wrongly assumed.
Highway 61
Revisited
The amber or purple-blue reflected coating tint of a UV(0) filter will be of zero effect. Those filters are not colored filters designed to modify or enhance contrasts with black and white films. As Dwig wrote before I ended typing this post, this is something very different. Modern multi-coated UV(0) filters have a green reflected tint for instance.
rfaspen
[insert pithy phrase here]
I was taught that the amount of reflection is most important. You want to see a light reflection with a colored tint, and easily see what's behind the filter. If instead you get a strong, mostly untinted reflection that you can't see through, toss the filter or remove the glass and use the ring for some other use.