Raw files are good for a lot of reasons, and one of the most useful is allowing you to make full use of your camera’s dynamic range after you take the shot. One place where this comes in handy is when you’re on the edge of having enough light to make an image. Perhaps you don’t have a tripod and your shutter speed is creeping down into motion blur territory, or you’re shooting in the near dark and already have your ISO up as high as you want to go.

A quick trick in both these cases is to dial in a stop of under-exposure, to speed up your shutter by a factor of two without changing anything else. This works easily if you’re in Aperture Priority. If you’re in shutter priority, you’ll want to double your shutter speed and then dial in –1 to make sure the camera doesn’t fiddle with your aperture to make up for it. If you’re in manual mode, you can of course just double your shutter speed.

This can work because your Raw file will still have quite a lot of data in the dark areas of the frame that you can pull back out. It is technically also possible with JPEGs, but much more effective with Raw images. If the result is that you can use a shutter speed that freezes the motion you’re trying to capture and couldn’t otherwise, it’s a success.

I have frequently used that technique when photographing stage performances where I just couldn’t get enough light for action shots. In that case I’d figure out the light level and go to manual metering, but with a 1-stop under-exposure. You can try 1-1/2 or even 2-stops, but you’ll be adding back just about as much noise at that point as you would by simply boosting your ISO further.

Image taken with default settings. Nikon D600, 1/10s @ f/5.3, ISO 6400 –.5 (to avoid blowouts)

I used the same tip for this photograph of the new lighting installation on the San Francisco Bay Bridge. Since I was strolling around I didn’t have my tripod with me, and was getting shutter speeds of 1/10s, even at ISO 6400. With my Nikon D600, as amazing as it is, I didn’t want to bump the ISO up further. The above photograph shows the slight blur from my hand-held shot at 1/10s. The image below is after I dialed in 1-1/2 stops of minus exposure, getting me to a more workable 1/30s.

Image taken with modified settings. Nikon D600, 1/30s @ f/5.3, ISO 6400 –2 (to increase speed)