Today I went to our twice-yearly photographic flea market. One of the things I scored was a Peak enlarger focuser, 2000 (Model I) Many years ago in another life whilst working in an industrial photo lab, I had the pleasure of using these grain-focusing units and believed them to be the best in the world. Well lady luck shone today and I picked one up, boxed and in new condition, with a BG filter. Now I had never seen or heard of this filter before, so I trolled the web, came up with the Peak sight, and discovered this bit of information. Use of the BG filter. When you want to obtain more correct enlarging for the black and white film, use the focuser after fitting the BG filter to its eyepiece. The use of this filter will permit the coincidence between the wavelength sensitive to your eyes and that to be enlarged. Upon getting home I decided to test this BG filter out. Firstly, I have to say as soon as I looked through the Peak I knew I was pretty much in darkroom heaven. I printed a 12x16 enlargement as sharp and focused as I could to the best of my ability without the BG filter. I was very pleased with the result. I then took out the BG filter, figured out how to attach it and looked at the grain, didnt really see much difference. However the BG filter is a push fit over the rubber eyepiece, there is a possibility that one could, or would, turn the dioptre eyepiece when fitting the BG filter. My enlarger is a DeVere freestanding 4x5 with the drop table and the front focusing wheels. When the enlarger is set and locked, nothing moves so basically you can be assured if its focused correctly it stays correctly focused. Focusing was done with the filters removed from the light path, and the lens stopped down to the printing aperture. After quite a number of test focusing, done with the Peak unit, with and without the BG filter, I concluded that there was a, just perceptible difference in the two practices. This was interesting; I then proceeded to make another print, with the focus set, using the Peak with the BG filter in place. This was the fourth print of the session; one print was 1/8 of a stop darker (first print). I took the remaining three prints into the house for the final arbiter on my prints, the missus. I laid the three prints out under our normal print-viewing situation and asked her to pick the sharpest and/or best focused print. As I have rather poor eyesight these days, this is almost a standard practice, so she didnt know this was a test of equipment. She picked the print focused with the BG filter in place! Now, I am well past finding the silver bullet in my photography, but I did know that the Peak unit would aid my failing eyesight in the darkroom. The BG filter though, was completely unexpected and also completely unknown to me prior to today. Have others out there experienced this little device and come up with similar results? I did search the APUG forums but couldnt find anything about this filter, which I find rather fascinating at the moment. By the way, the print my missus chose will be going into my local camera club competition. If Im going to test materials or equipment, I see no reason why the test always has to be of a line or colour chart. Mick.