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Garry Black Photography

Question:

Thanks for the useful and educational web site. After reading the section on filters by Benson and Wilson, I went out and bought their book and then bought a Cokin Blue-yellow filter. I tried using it in conjunction with graduated filters as Daryl Benson and Dale Wilson seem to have done but commonly end up, after rotating the filter to an acceptable position, with the graduated filter at a useless angle. This can be corrected by removing and remounting the Cokin assembly taking the position of the blue-yellow polarizer into account but this is cumbersome if it must be done for every shot. Is there an easier way? I have tried to find a standard threaded circular B/Y polarizer but they don't seem to exist.

Many thanks in advance

Answer:

I also have found the same problem with the Cokin 173 in that it is in a square mount and if you are using other filters with it, it proves to be quite a challenge to manage everything without getting any vignetting or getting graduated filters straight. There is an inexpensive way to convert the square P-173 into a screw mount filter. Remove the square holder from the P-173 (gently pry the plastic edges apart). Once you have the holder open, you will see that the filter is round. Next get a Cokin P-77mm adapter ring, the filter is slightly larger than the ring, you may be able to get the filter part way into the adapter ring, but not all the way in. The trick here is to heat up the adapter ring so that it expands; I used the low-tech approach, by placing the ring on top of a standard light bulb (that's turned on). When the ring had heated up (5 minutes) I quickly put the filter into the adapter ring, so that it was flush with the top and bottom of the adapter. There is no time to waste here, as the ring quickly cools (you might want to use gloves). Once the ring has cooled the filter will be firmly set in place, and you will now have a screw-in type filter. I screw the Y/B filter completely into the lens or another filter then I adjust the amount of polarization by turning the filter through 180 degrees.

The only problem with this set up is that you can't screw another filter into the front of the adapter ring, but you can screw the adapter ring holding the P-173 into another filter. So if I am going to use it with another screw in type filter I always screw the Y/B filter in last. If you really want to place another filter in front of the adapter ring, you will have to glue another adapter ring onto the front of your existing ring (you should do this before you put the glass filter in the adapter ring). The way that I get around using grad filters with the Y/B filter is to hand hold the grads instead of using the Cokin filter holder. If you're shooting in cool or cold weather hold the filter by the top, if you hold them on the bottom or by the side the heat from your hand will cause condensation, you'll fog up the filter.