4x4 Filter reflection?

B

Bokes

Well-known member
I was experimenting using a Tiffen Black Pro Mist 1/2 filter.
I have not used 4x4 in the past. I was shooting a head and shoulder interview with color gelled back light behind a muslin drop.
I was getting a small reflection (lens flare) in the filter glass that showed up right on my subjects forehead. It was coming from one of the backlights. I adjusted for it- but curious if this is a normal problem with 4x4's?

In the end- I shot the interview without the filter- but may want to use them at some point on location.
 
Re: 4x4 Filter reflection?

Filters are a flat piece of glass and typically not anti-reflection coated. As one can see by holding one and looking at the surface you get a pretty strong reflection. There is no solution other than to look for unwanted flares and reflections caused by filters and adjust light placement, flags etc to eliminate them to the extent possible.

Some very sophisticated matte boxes for film cameras have the ability to tilt the filters away from the "normal" square to the lens position for just this reason.

Bill Turner
Century Division
Schneider Optics
 
Re: 4x4 Filter reflection?

Why aren't they coated Bill? Wouldn't that improve transmission and contrast as well? Seems a shame to use high end 35mm primes and then slap an uncoated piece of glass in front of it :(
 
Re: 4x4 Filter reflection?

Shaw, that is a question that Schneider asked a number of years ago when we got into making filters for the motion picture and television industry.

The coating process normally requires a very good vacuum and high temperatures to get the anti-relection material to adhere to the glass well enough to withstand normal handling and cleaning.
The typical professional film and video filter is a laminate (two pieces of glass bonded together with the color or effects media sandwiched in the middle). The temperature would cause delamination.

New techniques for "cold coating" have been developed, noteably including a process proprietary to Schneider's factory in Germany. Schneider introduced coated filters under the trade-mark "MaxTran" that were all state of the art multi-layer coated. It was a resounding failure as a product.

While the advantage was demonstrable it significantly increased the cost of our filters that were already more expensive than our competitor (Tiffen). Even hard coatings are much softer than glass and more easily scratched. The rental houses who are the primary buyers of these large specilaty filters would not buy them, the project was discontinued.

As a note, Schneider clear filters are coated-- they are made from solid glass.

Photographic filters such as Schneider's B+W line of screw-in filters are available coated.

Photographic filters are mostly made from solid glass as well as being much less expensive to coat because of their smaller size permiting a much larger quantity to put in the vacuum chamber of the coating machine.

Bill Turner
Century Division
Schneider Optics
 
Re: 4x4 Filter reflection?

Bill: thanks for taking the time to provide a bit of education!

I had the same problem with 4x4 filters setting up a reflection pattern and discovered it had to do with the angle of the sunlight coming in on the lens (very late in the day, low hanging sun) and the lack of a good flag on the matte box I was using.
 
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