The 2 Stops Underexposure "Magic Bullet"

OK, you got me, there is no magic bullet. The truth of it is that you have to work hard and know what you’re doing. That said, this technique is a handy tool to have in the toolbox – I use it often to get great and predictable results.

I still remember the first time I tried this technique. It was four years ago in Hawaii. It was the perfect sunset, and I wanted to properly expose for both my background (the sunset) and my subjects.

My main problem when shooting sunsets, or shooting in the middle of the day (shooting against the sun) is that when I expose for the background, my subject will be an almost black silhouette. On the other hand, when I expose for my subject, my background (the sky) will be overexposed. As a strobist, my solution is using a speedlight or studio strobe to expose my subject properly. This is how I do it. (I’ll try to make it as simple as possible)

If you expose for your subject it will look like this. Your subject will be properly exposed but your background will be in highlights.

This is what it would normally look it if you underexpose for the sky. You get the details in the sky but your subject will be underexposed or a silhouette.

This “recipe” is the one I use, you probably should not use it as is. It has the sync speed for my camera and strobe, my ISO limitations and so on. Feel free to adopt and change it to your camera and strobe.

I usually start off at ISO 200, 1/160’s (Sync speed of my trigger and camera), matrix or evaluative metering and meter the sky (my background).
I move my aperture until I reach 2-3 stops underexpose to get the details in the sky, which leaves my subject underexposed.
This is where my flash comes in. With this shoot, I was using a 300w studio strobe (powered by a battery pack) thru Wescott Apollo Big Mama at full power.
The power of your flash will depend on your aperture. I know from experience that at ¼ power of my sb-600, it’s roughly equivalent to f8 @ ISO 200 at a certain distance. So, ½ is f11, 1/1 is f16 and so on. So, the last step is to adjust the power of my flash depending on the aperture, from the previous steps.

Another method of doing this is using a handheld light meter, OR just CHIMP it and use the histogram, if your subject looks underexpose add more power to your flash or move it closer to your subject.

Here is what it looks like with no flash – a dull silhouette.

And adding a flash – the model comes to life.

I was using a Nikon D3 with a 24-70 2.8 lens (pretty much a standard setup for me), and was shooting at ISO 200, 1/160, f22. I played around with an ND filter so I can shoot wide open at f2.8 (but still get the same 2-3stops underexpose for the background).

This is how it looked like at f22: