06/10/2013 11:02
Good morning, Jo Lund;
Four (4) things:
First; please accept my apologies for my confusion over your name. Now, belatedly, I should ask; "What name do you prefer that we use when talking with you?"
Second; how nice to hear that there really are people making their own photographic emulsion. Ron Mowery, Photo Engineer on APUG, and who used to work for Eastman-Kodak, will be pleased to hear that people really are doing this, and perhaps they are even using his book on that topic. With the loss of so many films, and even film makers, it is good to see that others are doing things that will in some way see that we can still use our cameras in the years to come, in spite of the varying financial fortunes of so many companies. I can also make glass plates for use with the SINAR and Speed Graphic 5 by 4 Large Format cameras.
Third; Yes, working with a very slow speed light sensitive material can be interesting. As mentioned, I use the ADOX CMS-20 and slow it down even more to ASA 5 when testing very fast lenses. The ADOX film has exceptional resolution, and I make my tests with the 1951 USAF Lens Resolution Test Targets outside in full sunlight, because that lighting condition is repeatable and reproducible by others wherever they may be. In that way it may be possible to directly compare one person's test results with another's, if we are also using the same film with the matching ADOX developer. And only by using a very slow film can we take a photograph outside using a normal camera with the common shutter speeds that go up to only 1/1000th of a second. Yes, there are cameras with maximum shutter speeds higher than 1/1000 second, but they may not be as common, and often they are more expensive also. For example, the Minolta Dynax 9 or Maxxum 9 does go up to 1/12,000th of a second, but they are not common, and when they are found available on the used market, they are expensive.
Testing lenses can be a challenge, and there are so many things to look for. With all of the possible aberrations, it is a wonder that we can take any sort of a clear and sharp photograph.
Fourth; The ASA (now ANSI) Shutter Testing speed tolerance for allowable errors in shutter speeds of 1/500 second and faster rises to plus and minus forty percent (40%). Most of the electronic shutters that I have tested are very good, and the Copal Square Metal Blind Vertically Traveling Shutter has proven to be remarkably accurate and consistent on the Kyoritsu EF-511NK1 Camera Tester.
One funny quirk about the Copal Square is the 1/125 second shutter speed. Back in the 1960s when the Copal Square shutter came out, it was advertised as the first focal plane shutter with a 1/125 second X sync speed for use with electronic flash units, while the more common cloth blind focal plane shutter had an X sync speed of only 1/50 or 1/60 second. But, every Copal Square shutter that I have tested, and that other professional camera technicians have tested, all come out right at just shorter than 1/100th of a second; usually right around 98 or 99 milliseconds. Every one of them. It seems that this was actually a case of a little bit of advertising or marketing license, and they were really playing with that 20% allowable speed error with their shutters and the "claim" of a 1/125 second X sync speed.
Enjoy;
Ralph
Latte Land, Washington
