Light Metering with a Dominant Light Source
Relying on an auto reading from your light meter ends up being a bit of hit and miss when you have chosen to work with a dominant light source. This assignment will get you thinking about where your light is coming from, and how your camera is going to handle it.
1. Can you see where the light is coming from here in my example with Jules in the late afternoon? I have a dominant light source, the sun. It’s coming from the left of the frame and backlighting her. But, we also have light illuminating her face as well. The light that illuminates her face is reflected light, it’s going from the sun, reflecting off the sky all around and all other objects, and then illuminating her face. If we only had the sun, and no reflected light, then it would be like standing on stage in a theatre looking up at the audience. We wouldn’t see anything, because there would just be that one bright spotlight shining on us.
So what I want you to do is set up a situation where you have your subject, in my case, Jules, and a dominant light source like the sun. You could do this indoors using house lights as well. Then put your subject’s back to the dominant light source and then aim your camera at the scene and see what happens in metering terms.
In my case there is a blanket of white sky that we can see behind her, and my reckoning is that this bright band of white goodness is going to play games with my light meter…why?…because the camera will take a midtone grey reading…remember…it will try to give you a midtone grey, Zone 5 reading for what’s in front of it, regardless of whether or not the subject in question actually belongs in Zone 5. Bright white sky belongs up in the Zone 9 or 10 range, it’s super bright. Meanwhile, my key subject, Jules, is the important element to expose correctly, because she is the hero of the shot.
Take a reading and see what you get. Here, at ISO 400 and F4.5, the shutter speed is reading in pretty fast at 1/800. The camera wants me to stop down, let less light in, to keep the detail of the sky and render it as a Zone 5 if possible. In my photo it’s still very light and some of the sky detail has been retained…but poor Julie’s face is looking pretty shadowy, she’s in fact underexposed.
2. Now aim your camera at the ground, to something that tonally looks like a mid tone grey. Meter that, take a photo, then raise your camera back to the original crime scene, and take another photo with the same settings.
My camera wants to open up a full 2 stops, to 1/200 of a second. That’s going to let a lot more light in, the sky will blow out, but I’m fine with that, because at the same time I will allow more exposure to Jules’s face, and give her the proper exposure she deserves.
ahhhh, that’s better! As a side note, the picture looks a bit flarey – a bit washed out. Flare is direct light shining straight through your lens. It’s actually non image forming light and results in that washed out look, it’s like putting a fine film of light all over your image. Like icing sprinkled on a cake, it’s even and indescriminate. Sometimes we can work that to our advantage creatively. In this case with Jules, well, it’s neither here nor there but is happening because of all that brightness bouncing off those white clouds in the background and coming straight down the barrel of my lens.
3. Now rotate 180 degrees so your back is more or less to the dominant light source, and your subject is more or less looking straight at the light source. We can see the sun is now over my right shoulder, and the way we assess that is by looking at the shadows of our scene. See the big shadow blob to the left of Julie’s nose in my picture below? Again, take a light reading, and shoot as the reading gives you. Here again, Julie’s white coat is going to confuse my camera. It’s pretty prominant in the picture and the camera will try to give me a Zone 5 for it…but no, we know this white coat is throwing off the meter, we know now from practice that we probably need to open up 2 stops, and shoot again.
4. Open up 2 stops, and what do we get? A fairly unflattering portrait of Jules, but at least it is more correctly exposed. 2 stops might have gone a bit far, because the shiny parts of her face on the right are looking quite bright now. But we can see detail in that deep nose shadow, her hair detail is much better, and the background is much better exposed now.
I hope that from completing Assignments 4 and 5 that you can now:
1. See why you can’t rely on your light meter exclusively to give you a correct exposure.
2. What you need to do to compensate for the camera’s mechanical limitations to get the correct exposure you want.
Keep and eye on my Where’s Beth? page. Dates are scheduled according to demand. Or, drop me an email to find out more about when Conquering the Camera workshops will next scheduled near you.
I want to see you well on your way to conquering your camera!
🙂 tell your friends about this course if:
a) they own a digital SLR camera
b) are still shooting on auto function
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Thank you for reading, it means a lot to me that you’ve stopped by. I hope you gained some new information and insights. I’d love to hear your comments and will reply asap.
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