Sunday, July 12, 2015

Meters Possess Knowledge, Not Wisdom

Manual Setting: 1/125 of a second, F 5.0, ISO 2000, Incandescent White Balance
This post's title is another Bob Schwalberg quote from one of the many articles he wrote for Popular Photography in the 1970's. A great time for photography. The Nikon F single lens reflex ruled supreme, Acufine allowed film to be exposed at ASA speeds of 1600 and greater, and in the darkroom, Kodak's resin coated printing paper allowed shorter print washing times. Practical autofocus and automated exposure settings had yet to be invented.

Many things have come of age in photography's Digital Age. Take exposure metering. Today, we take the accuracy of our built-in, through-the-lens metering systems very much for granted. Under even lighting conditions, they accurately assess the brightest regions (highlights), the darkest (shadows), and those regions in between (midtones). For the most part, the system works well, and when it doesn't, there are measurement options (spot, average, center-weighted) which can select a specific region for exposure evaluation, or skew the results towards a specific region.

For the most part, it's important to remember that the camera listens to every pixel in the frame, to some extent. It may listen more closely to the regions closest to the center (Center Weighted) or the tiny region defined by one of the focusing brackets (Spot). In the end, the final exposure determined by the camera  is a mashup of different values, and sometimes can be fooled.

This talented young cellist is Erica Mulkey performing as Unwoman at my nephew's birthday party. Just for kicks (and for the sake of my back) I brought only a Fuji X-E1 with a 18-55 2.8-4.0 kit zoom lens, along with a Fuji flash. I thought about bring some real lenses but decided to not get too involved. After all, it was a birthday party.

Under questionable lighting conditions, I always plan on establishing the "correct" exposure through sophisticated form of guesstimation. Normally, I establish a base exposure by:
  • Setting the ISO to the lowest value I think I can get away with. When I'm indoors, I usually start with ISO 800, always hopeful that there's enough light.
  • Setting the White Balance to one of the camera's presets. I chose Incandescent because of the hot stage lighting.
  • Setting the camera to Aperture Priority, and then setting the aperture to "wide open" for the lens I'm using. This is less complicated when one uses constant aperture lenses, as I do on "real" assignments. Here, I set the lens to F 4.0, my largest aperture at the longest focal length of my kit zoom. This way I know that my aperture will be constant throughout the zoom range of the lens.
  • Next, I mentally calculated my Minimum Shutter Speed. A Rule of Thumb says the longest hand-holdable exposure time (shutter speed) will to be the inverse of the focal length of the lens. This means that if you used a 50mm lens on a film camera,  the the longest exposure time you could use without resorting to a tripod would be 1/50 of a second. When using an APS sized (cropped frame) sensor digital camera, I multiply this number by a factor of 1.5, giving me 1/75 of a second, or thereabouts.
  • Finally, I took a shot. When I found I was getting excessively long exposure times, I increased the ISO to 2000. I shot again.
Aperture Priority: 1/34 of a second, F 4.0, ISO 2000, Incandescent White Balance
In theory, the camera's meter properly evaluated all of the values (shadow, midtones, and highlights), crunched the values, and chose this as the proper exposure setting for the 2000 ISO setting. Judging from the burned (or "hot") highlights, I needed to decrease my exposure time. I set the camera to the Manual exposure mode setting. I knew the camera chose 1/32 of a second for this shot, and decided to drop the exposure time by a factor of 4 (2 F-Stops). After a bit of playing, I arrived at my final setting of  1/125 of a second, F 5.0, ISO 2000. Somewhere along the way, I decreased the aperture by 1/3 of a stop. The 1/125 was briefer than my calculated maximum exposure time of  1/75 of a second, so my images should be reasonably sharp. This doesn't take subject motion into account, so I still have to wait for lulls in the action when I press the shutter release.
Manual Setting: 1/125 of a second, F 5.0, ISO 2000, Incandescent White Balance
You can see that allowing the background to go completely black works, in spite of my meter's best efforts to interpret it as "gray". Dropping the suggest exposure makes the image truer to life and allows me to keep lots of detail in the midtones and highlights. I still have some exposure latitude in post production, so the highlights could be darkened a bit, if I wished.

Manual Setting: 1/125 of a second, F 5.0, ISO 2000, Incandescent White Balance

The beauty of working manually is the consistency of the exposure. When I recomposed the image with much more "dark space", the appearance of the flesh tones remained constant. And since I was pretty sure there would be no variation in the intensity or location of the stage lights, I was free to shoot without giving my exposure another thought. Yeah, I wasn't happy about the "Exit" sign, but it was there, and I didn't clone it out.

The nice thing about the X-E1 is the ability to preview the image without taking the camera from my eye. This allowed me to monitor my results in the viewfinder, thus avoiding the "shoot and chimp" routine. This saved a lot of time. I really like the Fuji in available light situations when I have lots of time to set my controls. It really sucks as a "run and gun" camera. Still, this doesn't keep me from looking at fast Fuji prime  lenses, however.