Re: Exposure compensation for small apertures
Mechanical shutter are lesser accurate-precise by their innate workings. Thus was born the electronic shutter which improved this in various ways.
The alternative method to achieve accurate-precise exposure of film is to used high quality electronic strobe-flash which is not nearly as dependent on shutter open-close times. Or why this was the overly preferred method of color transparency film exposure required for proper high quality color transparency image work back in the day. A properly calibrated and stable electronic flash system of lens aperture, film batch tested for actual film speed and all related produced consistent and reliable image results to 1/3 f-stop or better.
Bernice
Quote:
Originally Posted by
Tin Can
I notice some want 1/3 stop accuracy with film aperture and shutter speed
What is the ANSI spec?
Maybe plus/minus 30 percent!
Re: Exposure compensation for small apertures
I know most disparage my 4 Paul C Buff Einsteins, they are what I could afford
But I can precisely adjust them using my Sekonic L758 without rechecking IRL flash exposure
I do like that
3 Attachment(s)
Re: Exposure compensation for small apertures
Quote:
Originally Posted by
Tin Can
I notice some want 1/3 stop accuracy with film aperture and shutter speed
What is the ANSI spec?
Maybe plus/minus 30 percent!
Randomly selected from random LF shutter service manuals (Graphex and Synchro Compur):
Attachment 227048
Attachment 227049
Re: Exposure compensation for small apertures
Little exposure errors can add up fast. For color transparency usage, even a third of a stop might be objectionable if one is working on the edge of contrast limits.
Re: Exposure compensation for small apertures
Unfortunately, I see too many naive people here thinking they don't need to take their shutters' efficiency into consideration since they do not use the 1/500s speed.... Sorry that's not correct. The difference in shutter efficiency is insignificant at speeds about 2 stops longer then the longest speed that is 50% efficient, i.e. 2 stops slower than the longest speed at which the shutter blades open and immediately close, without any time gap. With different shutters, those slowest 50%-efficient speeds differ a lot. It is a 1/200s on my dial-set Compur #2 but it is a 1/50s on my Ilex #4, and it is a 1/15s on my Prontor-Press #1. That means I can forget the efficiency issue with all speeds from 1/50s and longer with my Compur but only with the 1/10s and longer with my Ilex and only from the 1/4s and longer with my Prontor-Press. A 1/10 and a 1/4 are not the shortest speeds usable in LF....
(That also means that those published exposure compensation tables for a 'general shutter' just can't be correct. Because there are no 'general shutters' in the real world.)
And another point: what I have read in special technical literature is that shutters are usually calibrated to make their speeds accurate at 2 f-stops smaller than the maximum aperture, not wide-open. That way the effective speed deviations are smaller at all the rest f-stops.
But still no exposure compensation is actually needed for a film like Tri-X....