Pentax Spotmeter V, copyright 2016 Douglas Stockdale
In my earlier post about determining the exposure index (EI) for the two 21mm extension tubes on my 150mm Sonnar Hasselblad lens, I was pinged with some questions about the +1 exposure compensation conclusion. I am realizing that with the advent of digital photography which really gained traction in the early to mid 2000’s, there is an entire generation of digital photographers who are not familiar with film and manual light meters, which should not be much of a surprise, but sometimes the extent and breath of the non-analog experience is interesting.
In the zone system exposure parlance you start with your basic EI, in this case the ASA of the film is the basic or neutral starting point. My Fiju Reala 100 color film has a ASA of 100, which I dial into my Pentax Spotmatic V, a manual 1 degree light meter. I acquired this current meter many moons ago with my earlier Minolta 1 degree spot has a “traumatic” moment (yep, while hiking I dropped in on the rocks, pretty traumatic for both me and the only light meter I had with me).
To complete my exposure compensation test, I varied the f/stop by a half stop stop per exposure. A plus one (+1) stop essential doubles the amount of available light during the film exposure over the neutral setting As example, I had set neural at 1/30 at f/4, thus the +1 was 1/15 at f/4 to double the amount of light during the exposure. I extended the test exposures to a +2-1/2 stops, which began to really over expose the film. The gray card I was photographing and film density was visually best to me with only the +1 stop. Now I could meter the scene with my light meter at set for the film ASA (e.g. 100) then take that meter reading and open one stop or alternatively I could set my meter ASA to 50 (half of the 100) and use the resulting setting.
The later option of altering the film ASA takes a bit less thinking ;- )
Btw, the nice thing about this 1 degree spot meter is that it has a number of settings; f stop for the lens aperture, T (time) for the exposure duration, ASA for the film speed and then something called the Linear Scale, which so happens is also a setting available with the older Hasselblad lens like my 150mm Sonar. Inside the meter, the linear scale is the value shown during the metering function. Once the Linear scale value is selected on the lens, the appropriate f stop and shutter speed T are coupled on the lens and when you change either the f/stop or the exposure duration, the other automatically changes due to the coupling function.