Digital Exposure by Trial and Error
I love my new Nikon D100 digital SLR. It captures amazing images and the immediate feedback in the field is phenomenal.
The D100 isn't perfect though. Like its close relative the F/N80 film SLR, it won't meter with lenses that lack internal CPU's. All auto-focus lenses work just fine, but with few exceptions, manual focus lenses won't meter. I would have appreciated it if Nikon had not chosen to skimp on this feature, but obviously they had to make some hard choices to get the price point they were looking for. It's still a great camera.
Suppose, however, that you have some manual focus lenses that you'd like to be able to use with the D100. While it is possible to get many manual focus lenses converted to work by adding a metering chip, this isn't as necessary as one might think.
The fact that you can see your results on the LCD panel makes it possible to get results without metering though a technique I like to call "exposure by trial and error."
First, pick an exposure — any exposure. Just guess. Take a shot and view it on the back of the camera. If the results are too bright or too dark, estimate how much you are off by, adjust either your aperture or shutter speed appropriately, and try another shot. If the image is completely black or white, you are off by at least three stops. Repeat the process and you will be surprised at how quickly you can zero in on a correct exposure. Be sure to use the histogram to confirm what you are seeing.
The series of images here illustrate the technique. All images were shot at f/16 for adequate depth of field. I started with a shutter speed of 1/125 second, for no other reason than that's what the camera was at when I turned it on. The result, as you can see, is all but completely black. I changed the shutter speed to 1/15 second, an increase of three full stops for the second shot. The image clearly registers now, but is still too dark. The white markings are closer to medium gray than white though, and the blue portions are almost black. Upping the exposure two more stops to 1/4 second for the third attempt proved to be a winner.
I've found it usually takes me about 3 or 4 shots to get a good exposure. Assuming you are shooting something that doesn't move, this can work quite well. When you get what you want, simply delete the ones that didn't work. This same technique can help with other complex exposure problems including twilight and fill flash shots so I urge you to experiment. Digital can be a great learning tool.