Filters matter which way they point?

[Robert]

A while back I bought a set of filters. The filters are from some place in Eastern Europe but the main reason for buying them were the two step up rings [40.5 and 52] that I just happened to need. The filters worked just fine and I guess are of reasonable quality. They've been mostly used with the 35mm camera's meter so I didn't really worry too much with exposure. On the camera with the broken meter I just used the filter factor that's on the filters. Everything worked fine so I didn't worry.

Well today I decided to check the filters with the meter to see if the filter factors actually match. At first the numbers seemed way out of wack. Then I noticed I was holding them wrong way out. Flipping them over the numbers matched up nicely. I then checked some Hoyas [Are these made in Georgetown?-)] and they also did the same thing. Is this normal? Is this just one more case that I shouldn't check things to avoid confusing my self? Or does this mean the quality of the filter is lacking?

 

[Donald Miller]

Interesting observation, I checked my filters because you aroused my curiosity and I found that mine are exactly the same no matter which side is nearer the lens. The only time that I could see a filter orientation making a difference is if it were polarizing the light rays striking it. It might be interesting to check your filters effect against various orientations to the sky and by rotating the filters orientation as to position of up and down on the perimeter of the filter mount.

 

[Robert]

I just rechecked. This time I used a window with a large over hang. They are much closer this time. All except one that's still off. One thing I'm wondering if it's me getting my fingers in the way. I guess I should make a cardboard holder and tape it to the window or something.

 

[Thilo Schmid]

Robert,

make sure that your meter does not catch any reflections from the filter glass. Hold your meter as close as possible to your filter.

 

[Robert]

That must have been it. I basically stuck the meter right onto the filters and things seem fine. I guess I should just trust the manufacturer.

 

[Robert Kennedy]

That last line will come back to haunt you....