double outlines in reflections on filters

[seany65]

Hello all,

I've just noticed that several filters that I recently bought show double outlines in parts of the reflections on their surface. The second outlines also rotate slowly as the filter is rotated, meaning the part of the main reflection that has the extra outline changes.

I have a BDB 40.5mm "Planoptic" yellow filter which shows a double reflection, and I have the merest hint of a vague recollection of some blurb that I may have read years ago, which I think suggested that a double reflection was a feature of "Planoptic" filters.

So I was wondering if anyone has any info as to whether a filter that gives double reflections (however minor they may be) is showing that the filters isn't quite as well made as it should be?

Some of these filters are Photax ones, but I have other Photax filters which don't show any extra lines in the reflections on their surface.

Any help would be much appreciated.

 

[boojum]

Yes. I have some nice B&W's that give me ghost reflections of points of light in some night shots. If I remember I take off the UV filter to prevent this. But bright lights in a dark background have been a bugaboo.

 

[seany65]

Thanks for the reply boojum. I can't see any "extra" outlines when I look through the filters, just when I'm looking at the reflections of objects that are in front of the filter that I can see on the front of the filter.

What I think you are seeing are the reflections of the points of light reflected from the front surface of your lens onto the rear surface of the filter, and then being reflected back into the lens. You'd think B+W would know how to make filters that don't do that. I've never noticed it with any of the dozens of Hoya filters I've owned over the years. I do have a lot of other makes of filters, many of them probably not coated, but I've really only used the UV filters so far.

 

[boojum]

Thanks for the reply boojum. I can't see any "extra" outlines when I look through the filters, just when I'm looking at the reflections of objects that are in front of the filter that I can see on the front of the filter.

What I think you are seeing are the reflections of the points of light reflected from the front surface of your lens onto the rear surface of the filter, and then being reflected back into the lens. You'd think B+W would know how to make filters that don't do that. I've never noticed it with any of the dozens of Hoya filters I've owned over the years. I do have a lot of other makes of filters, many of them probably not coated, but I've really only used the UV filters so far.

You may be right about my problem. All this stuff is mysterious to me. All I know for sure is that there are a bunch of little pixies inside the camera with brushes who make the pictures, right?

 

[seany65]

Well, yes, there are pixies with brushes inside the camera. They paint using "Pointillism", and the faster the film the bigger the dots they have to use to get an image on the neg.

 

[boojum]

Well, yes, there are pixies with brushes inside the camera. They paint using "Pointillism", and the faster the film the bigger the dots they have to use to get an image on the neg.

I knew it, I knew it. ;o)

 

[seany65]

Don't forget that these Pixies are in a constant war with the outnumbered, (except it seems in digital Leica cameras), army of Gremlins who try to ruin the photo.

 

[boojum]

Don't forget that these Pixies are in a constant war with the outnumbered, (except it seems in digital Leica cameras), army of Gremlins who try to ruin the photo.

I don't know about your camera but the Gremlins have screwed up way too many of my perfect photos. I am looking for Gremlin powder to get rid of them. Then my pictures will all be perfect, again. ;o)

 

[peterm1]

Thanks for the reply boojum. I can't see any "extra" outlines when I look through the filters, just when I'm looking at the reflections of objects that are in front of the filter that I can see on the front of the filter.

What I think you are seeing are the reflections of the points of light reflected from the front surface of your lens onto the rear surface of the filter, and then being reflected back into the lens. You'd think B+W would know how to make filters that don't do that. I've never noticed it with any of the dozens of Hoya filters I've owned over the years. I do have a lot of other makes of filters, many of them probably not coated, but I've really only used the UV filters so far.

Reflections off the back surface of the filter was my first inclination too. As I understand it every time photons makes an air- glass or glass - air transition there is a chance some will be reflected back in the direction they came from. This effect is what filters are supposed to reduce. I am not so clear on why that may not be the case in these instances, however.

 

[boojum]

Reflections off the back surface of the filter was my first inclination too. As I understand it every time photons makes an air- glass or glass - air transition there is a chance some will be reflected back in the direction they came from. This effect is what filters are supposed to reduce. I am not so clear on why that may not be the case in these instances, however.

My solution is to skip the UV at night. Not a lot of UV around then and there are a lot of situations where there are lights against a dark background. And that is where the problem has been.