We visited, a small group of photographers and I, a cathedral to observe the light. Shafts of morning sunlight streamed in through windows high in the arched ceiling, part of the builders plan for a play of light that would stream in with changing shafts moving over the altars and strategically placed statues. The rays of illumination hovered dramatically over the face of the Virgin and the crucified Christ, making a chiaroscuro presentation that with long study and meditation while one prayed, would cause the statue to appear to move. Surely this would impress all but the most jaded of the faithful and could not help but stun the children.
Later builders forgot the importance that the 16 Th Century builders had given to these windows and covered them with colored glass leaded in. Wealthy patrons could dedicate these windows and have their name inscribed for perpetuity somewhere in the church. That was progress.
With the coming of electric light, the windows lost their importance completely as electric spotlights, wall washers, and floodlights served the same purpose though not with the magic of natural light. The natural light streaming in seemed to be God-sent and when it illuminated a statue or altar it became a profound message from the heavens, so much more dramatic than a man-made light. But we embrace progress even when we loose something.
Our teacher that morning noted that our cameras with their automatic exposure, matrix metering, and auto-focus zoom lenses have offered the same promise of technology and with that we have gained much but we have lost something as well; we have forgotten how to read the light. God's light she called it.
She pointed out that we let the camera take over and that we merely hold and point it, pressing the button when it tells us it is ready and hoping that if we press enough times that we will make a good photo.
How many of you dedicated amateurs learned to think in terms of F-stops she asked? Few hands went up. How many can estimate a reciprocal increase in shutter speed when they decrease the aperture size. Fewer hands. She made her point, We have lost the knowledge and we just shoot frame after frame hoping to get lucky, not really knowing how to read the light.
We had visited the cathedral to rediscover this light, observing how the 16th Century builders had oriented the church east and west, placing the altar in the east while the main entrance they placed in the west. Morning services would have low light streaming in through the window behind the altar giving a rim light to the statues and the priest as he said mass. Services later in the day would have light streaming in from the side, sending a shaft across the altar from our right to our left. Because of this hard and intriguing light we were able to study how a lack of control over the setting on our camera for exposure in mixed light would compromise our photography.
First we used our camera's spot meter to read the reflected light that streamed in through a high window and skimmed the altar with hard side light. We had a reading of f8 at 1/60 of a second with a 100 iso digital setting. A reading of the shadow area gave us f-2, the widest possible aperture for most of our lenses and it gave us a shutter speed of 2 seconds. Counting by stops or steps, we recorded f-8, f-5.6, f-4: a three full stop difference. We continued counting our shutter speed in full stops: 1/60, 1/30, 1/15, 1/8/, ¼, ½, 1 second and then 2 seconds: ten full stops between the lighted area and the areas in shadow. Those not familiar with f-stops soon learned that each one doubles or halves just like film speed numbers: ISO 50, 100, 200, 400, 800. Once we understood this difference between the light area and the dark area and the limits of our digital cameras to reproduce that extreme spread between dark and light, we realized that in order to make a decent photo without shooting many frames to bracket and get lucky, we must set our cameras to manual if we have such a setting and then tell the camera what we want it to do.
Before we set the camera controls we needed to ask ourselves a few questions our teacher pointed out. Do we want the white robe on the statue to have detail in the highlights? If so we must set our camera to f-8. at a 1/60 of a second, this setting will render the highlights in the white areas to a mid grey and preserve highlight detail. The downside to this setting will be loss of any detail in the shadow areas. If we wanted detail in all the shadow we must set our aperture no more than one stop above the shadow reading of f2 at 2 seconds. As we determined by our stop count, this setting will underexpose the shadow area by one stop, preserving detail in the shadow area but the lighted areas will loose all detail to an 8-stop overexposure A compromise would be half way between: F4 at 1/15 of a second, but neither setting will properly expose everything. We realize that this photograph, like many of our photographs, will be a compromise were we must choose our most important subject and expose for it, letting less important elements of the photograph fall where they may.
This visit to the cathedral had presented us with all the challenges and more of exposure control that we would encounter in almost every photograph that we make. Our teacher remarked that the one time when exposure control presents no problem is during an overcast day when nature diffuses the light leaving us with not more than 2 stops of difference in the light. Otherwise we must always control the camera and decide where we want the exposure to fall.
We made our church interior exposures that day knowing that they would not be perfect. The ten-stop spread in exposure far exceeded the ability of our digital cameras to record but the exercise forced us to take control of our cameras, to read the light, and to make the photo that we wanted to make not the one that the camera chose to make. That day our photography started to become more predictable, we had taken control of our photography and we could read the light. The camera would be just a tool and the process a compromise, but we would be much more a part of the process and the camera would never again come between us and God's light.