Ok, I know I do not sit on the bleeding edge of photographic technology, even my SD14 was only purchased after Sigma had it out for a couple years. I still feel at home with manual cameras, film based imaging technology, and first generation image stabilization. ( A tripod )
From the posts I've made, I'm sure most CiC members realize I delve into the numbers, calculating hyperfocal distances, depth of fields, exposure values, and generally working in photography as an engineering and scientific discipline.
So, in my usual preparation for some astronomical star field shots, part of experiments in film preexposure to allow the film record an image with less incident light, I wanted to set the focus between a calculated hyperfocal distance and ∞ so that I know I'd have an optimal focus and not have to rely on setting the focus by eye. A Note to Newbies - Auto Focus will not work with low light or point sources, in this case it has to be manual.
First off, all my "modern" lenses focus beyond ∞, which is why I decided to pursue the hyperfocal distance route. That's no big deal, a quick and dirty bunch of calculations in a spread sheet has that done.
Now the problem comes from my "modern" lenses, No Numbers !! At least not where I need them to be ! The "on lens" focal scale for my normal to wide angle lenses runs from 1m or 2m straight to ∞ ! The best "modern" lens is my old Sigma 70-300 Macro Zoom ( it was a kit lens with my SA9 ) that at least goes from 8m to ∞.
First Question: How do I set the focus of my 28mm lens set at f/1.8 between the hyperfocal distance of 87m and ∞ ? Especially when the lens can focus beyond ∞ and I know the scale itself may not be entirely accurate. If the lens focal adjust ring stopped right at ∞, this would be a non-issue.
I do not accept settling for f/22 just to bring the hyperfocal distance down to 7m.
Note: These hyperfocal distances come from calculating for a Circle of Confusion of 5um, for my needs the standard 30um is too large. For a star field astronomical photo, a smaller Circle of Confusion means the film can image fainter stars. Equivalent to going from ISO 200 to over ISO 1000 with no increase in noise.
A tool like dSLR Focus will not help here, I'm using my Sigma SA9, a film SLR, but the lens is all digital age technology.
Second Question: When did lens design and lens manufacturers so extremely compress the ∞ end of the focal scale ? I know the scale is logarithmic, but 1m to ∞ is a bit much.
( I know - Another weird post )