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Christopher Grey

Underexposure as a Creative Tool

By Christopher Grey
Published by Sekonic

Sure, you can use a light meter to get your exposure precisely right. But what if you want something different? Lighting expert Chris Grey explains how to use underexposure and image processing techniques to give your images a distinctive look.

Photographer Chris Grey is an expert on lighting. He's written seven books on the subject, teaches classes and workshops, and is a strong advocate for precise control in the studio. To see more of his work, or to find his books and DVDs, visit his Web site.




I’m always looking for ways to separate my work from my competitors'. Part of that never-ending search is looking for new ways to break the rules, methods that give my work a look that my competitors have trouble figuring out. Using underexposure for creative purposes is just one of the tricks in my bag.

We know, of course, that underexposure by more than 6/10ths of a stop will result in images that, while they can be reclaimed in Photoshop, will never look "normal." By that I mean the images will never show the subtleties in skin tone and lighting that you may have envisioned when the images were created.

But what if you don’t want them to look normal? What if you want them to look über-normal? Understand that I’m not giving you license to screw up. As with any good trick, the effects of underexposure (and its relationship to Photoshop) must be understood before it can be put to good use.

The first image below was made with very simple lighting. My key was a 36-inch umbrella. The hair light was a medium softbox, which explains the consistent side light. I placed a black bookend just to the side of the model, to keep flare from the softbox off my lens.

I metered my subject and powered the lights evenly, then reset the power on the key to be 2/3 stop less. I know this looks pretty good on your screen, but any lab prints of it will look a bit muddy without adjustment. You can see from the histogram the image is lacking brighter tones.

We can fix this easily, but since we’re at the limit of exposure latitude, we can expect to see some changes beyond simple lightening. It’s a good idea to convert the image to 16 bits before doing any exposure adjustment in Photoshop, and then convert back to 8 bits when you’re done. You’ll fool Photoshop into thinking there’s more information in the image than there actually is, and the final histogram will be much smoother.

I’ve adjusted the histogram by moving the brightness slider right to the edge of the working pixels.

Look what happened here: The whites from the hair light brightened considerably, to the point of being blown out but framing her body quite beautifully. Notice also how the shine on her face brightened, giving her skin an extra glow. This is subtle, but gorgeous.

I wanted to see what would happen to specular highlights if I pushed the limits quite a bit more.

I used the same lighting scenario, but with a couple of changes. I swapped the background by propping up a piece of painted Styrofoam behind the model. I moved a black bookend in from the left to throw a shadow on about half of the background. I also added a white bookend to the camera-right side to open up the shadows. The key light was powered back up to its original strength, but I cut the hair light back by 2/3 of a stop. I knew it would still register as additional light, but I didn’t want it to be brighter than the key. Even with the extra gobos, it was still just a simple two-light setup.

After a wardrobe and hair change, we were ready to go. A quick spritz with a spray bottle created the extra specular highlights I wanted. This image was properly exposed.

The first set was underexposed by one full stop, and the histogram adjusted the same way (after converting the image to 16 bits). The resulting bright speculars add a lot of visual interest. Color contrast has increased a bit as well.

My last series was underexposed by two full stops. It's definitely too dark to be considered salvageable by any but the deranged. I asked my model to turn a bit, so her arm would shadow her face, as I was curious what would happen to such a dark section of the image.

The result is very interesting. I found I needed to bring up the midtones about 20% in addition to the highlights. Color contrast increased even more (this could be fixed with a Hue/Saturation adjustment layer in Photoshop), but the overall relationship of the tones stayed true.

There’s a quality about these images that’s almost larger than life, and I’m certain you’ll find a place for this approach in your mental gadget bag. But if you’re at all worried about it, shoot the images in raw+JPEG mode. If you don’t like the JPEG, or decide you want a correctly exposed image, make the appropriate exposure adjustment to the raw file before processing. Conversely, you could shoot strictly raw and process a correctly exposed image to an underexposed TIFF or JPEG.

Text and images © Christopher Grey.

Category: How-To
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