Quote Originally Posted by Ken Nadvornick View Post
And it's confusing me as well. The #19 filter should cut off virtually ALL of the blues and greens. In other words, when in place you should see no blue and/or green bands at all.

Before my successful (pre-fogged) safelight tests I fired up the Duplex, let it warm for ~30 minutes, then looked at the CD reflections unfiltered. In addition to the massive yellow sodium doublet, I saw the much, much fainter blue and green spikes. I also saw the extra deep red spike.

Then while looking directly at those spikes I interposed a single layer of #19 filter. The blue and green spikes disappeared. When I removed the #19, they returned. Back and forth.

Later, when I performed the safelight test I was able to leave a sheet of Kentmere Bromide #3 graded paper out for ~30 minutes with no hint of fogging.* As you may know, bromide papers are very fast. It should have responded to any blue light present. But it didn't. It remained pure white. (Even checked with a reflection densitometer to factor out my subjective eyes.)

So as I said, I too am confused.

Also keep in mind that if you use a cover sheet of Rubylith you will likely be filtering out all of the yellow sodium light as well. At least in a perfect world. I've never tried it myself, so I don't know how much will pass. Maybe only that secondary red spike I mentioned above?


* Apologies, as I earlier identified the test paper as Ilford MGIV. It was actually the Kentmere Bromide. The Ilford was used for my red LED safelight testing.
Well, allow me to make it even more confusing: I did the exact same thing that you did with filtered and unfiltered reflections on the CD. Unfiltered, I saw the blue and green bands, and also the massive yellow sodium band and the deep red...exactly as expected. With the #19 filter in place, the yellow and red were unaffected and the blue was entirely cut out...but the green band was still dimly present. I actually managed to do a side-by-side comparison with the #19 filter halfway covering the sodium lamp, and although the green band was attenuated it was, as aforementioned, present. So, I don't know what to make of that, because there should be very, very little green coming through the #19 filter...but it was most assuredly there, and likely - in my opinion - burning the paper.