Pinhole Filter Exposures

Anyone have any ideas on how to calculate pinhole exposures using yellow or red filters? How would you add filter factors to pinhole pictures?

Yellow & Red filters are straight cut. A K-2 is generally 1 1/2 f stops, and a 25A (deep red) around 3 1/2 f stops. What ever your "base" exposure for the pin hole, multiple by these factors. Receprocity might kick in so go +1 stop over the calculations to see if it all works. Bill

I use TMAX for pinhole so the reciprocity is minimal. When you say "multiply by these factors," does that mean 3 1/2 times the "base" for red?

If your exposure without a filter was 1 minute, then with the red filter it would be 3 1/2 minutes. I'm not familiar with reciprocity failure for TMAX films, but I would be surprised if there weren't some issues with reciprocity failure with the long exposures that pinhole photography requires.

I'm pretty sure the data sheets for T-max carried a nomograph for calculating any reciprocity correction.

 

So I don't see any issue. Just multiply the base exposure time by the published filter factor, and then look up any reciprocity correction on the T-max chart.

Well, reciprocity for Tri-X is humongous, but T-max not so much. According to one chart, using as an example a 30s indicated exposure, Tri-X would be 4m 50s, T-max would be 50s, and Hp5 or Hp4 would be 2m 35se.

Oddly enough, according to another chart, T-max requires slightly less adjustment for filters than other B&W films. Accordingly, T-max would require a 3/8th-stop exposure increase with a yellow filter, while other films would require 1-stop. Deep yellow would require 1-stop with T-max while other films would require slightly more. Red would be the same in both cases, but yellow-green, a filter I regularly use here in the South West, would require a 1 3/8-stop increase while other films would require 2-stops. No idea if there is any truth to this.