Hi everyone. In another thread we are discussing Guide Numbers for using flash bulbs, specifically Sylvania 25 and 25b. If anyone has experience with this and has actually run film using these bulbs (25 and 25b class M) could you please shed some light on the most ideal guide numbers to use when shooting Tmax 100 (4x5 and 35mm)? If you've found better bulbs and/ or guide numbers please share your experiences. I will be running some tests to compare a few sources of guide numbers but I have a limited supply of bulbs at the moment so a tested starting point or a blatant solution would be hugely helpful! I'd like to waste a few of these bulbs as I have to so that I can use them for more serious shooting projects. Just an FYI, I'm running Tmax 100 4x5 through a modified Speed Graphic Pre-Anniversary with a Carl Zeiss Jena 135mm Tessar lens and I'm running Tmax 100 35mm through an Argus C3. Using both Sylvania 25 and 25b class M bulbs. Thanks!!