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How-to's

Specular Highlight Control

User


Keywords: flash, studio, lighting, filter, guides, tips

This is the 6th and final part of the learning to light series with Josh Larkin.

In my last post I started looking more closely at diffuse and direct reflections and how both reveal the form and surface texture of a subject in a photograph. Through my exercises, I was able to exert better control over the placement and look of direct reflections, or specular highlights, and now I want to apply that knowledge to a subject where this has a dramatic impact on the end result: metal.

Photographing Metal: It's all about the specular

Specular

1/250th f11 ISO100

Photographing metal is a pure study in the family of angles. Even if, like me, you have little interest in commercial photography where you might be photographing metal objects, running through exercises targeted specifically at photographing metal will provide you with a much better understanding of how light behaves, which is applicable to all types of photography. For my tests, I chose a pretty common subject for these types of exercises - a kitchen utensil, cutting board, and a tomato. Here's why. I knew that the cleaver, made of metal and a black handle, would provide almost entirely direct reflection, which is mainly what I was wanting to explore.

The cutting board, being a matte surface, would provide almost entirely diffuse reflection, so this part of the subject could be lit with either the same light source used for lighting the cleaver, or, a separate source positioned outside the cleaver's family of angles, therefore not creating speculars on the cleaver. The tomato produces both direct and diffuse reflections, so it seemed like a good object to add to the mix. For my initial shots, I wanted to get a better feel for how the specular highlights would appear on the tomato and just test to see whether this would affect the look of the cleaver. Note that for all tests I've set my D7000 to it's max synch speed, 1/250th of a second, so that no ambient light would affect the exposure. A photo taken with my flashes turned off would produce an entirely black image.

 

Specular-1

1/250th f8 ISO100. SB600 at camera right, approximately 3 feet away from subject, set to 1/16th

For shot one, above, I positioned an unmodified SB-600 to camera right, set to 1/16th power and zoomed to 24mm. There are a number of visual cues here telling us the type and quality of light I'm using -- the hard shadows are one cue, but the other dominant sign is the bright specular on the tomato. Being a direct reflection of the light source, which is fairly small for the subject, the reflection is so strong it's blown out at its center.

Before setting up the light position, though, I took a quick guess about where the family of angles for the cleaver blade would fall. I decided that positioning the light to camera right would fall outside the family of angles for the main face of the blade, therefore leaving the blade essentially unlit since my camera wouldn't record any direct reflection from the blade. For my next shot, I wanted to get rid of the hard shadows and that bright specular on the tomato, but still leave the cleaver blade unlit. Simple enough. Leave the light in the same position, but make it appear larger relative to the tomato. A shoot through umbrella later, flash power dialed up to 1/4 power, and the result was the same image as before, but softer shadows and a less intense specular on the tomato.

Specular-2

1/250th f8 ISO100. Shoot through umbrella added, flash set to 1/4th power

Interestingly, in both images the metal along the blade edge and in the handle are reflecting light back into the lens, so they are appearing as bright metal to the camera. This is because the family of angles for those parts of the cleaver are different from that of main part of the blade. I hadn't factored this into my thinking when setting up these initial shots, and so decided to change my approach a little bit for my attempts at lighting the blade while separately lighting the rest of the scene. Moving things around in the scene, I'm now shooting the subjects straight on looking slightly downward. The goal here was to light the scene without producing a blown out specular on the tomato, and then add in a second light source to create a direct reflection from the cleaver blade.

I started by figuring out what the family of angles would be for only the cleaver blade. In the diagram below, which is a side view of just the camera and cleaver, I can see that in order to get a shiny blade, my light will be positioned above and behind the scene. Any other lighting positioned outside of these angles will not affect the appearance of the blade.

 

 

cleaverFamilyAngle

Cleaver Family Angle

My next thought here is how the two lights will play together. I already know where my light needs to be to light the cleaver blade, but I haven't figured out how big it will be. If I spend some time working with gobos, I could get the light to only illuminate the blade and very little else in the scene. Alternatively, if I use a large light source, I can fill the family of angles for the blade and add some light into the rest of the scene. In fact, I could light the whole scene this way, but that throw shadows towards the camera and leave the front of the tomato in near darkness. That being the case, I decide to set up my first light to camera left, about 45 degrees from the camera's axis, and slightly above the scene. I'm using my trusty shoot through umbrella to keep the shadows soft and the specular on the tomato less intense. Again, I have my shutter set to its max synch speed, negating any ambient light in the scene.

specular-3

1/250th f11 ISO100. LumoPro LP160 fired through an umbrella at camera left, set to 1/8th power

LumoPro LP160 fired through an umbrella at camera left, set to 1/8th power) This shot is pretty dark, but that's okay, and here's why. I've decided that the second light will do double duty, filling the family of angles for the cleaver blade and also providing a substantial amount of fill for the entire scene. To accomplish this, I set up my SB600 just to the right of the scene and angle the flash head pointing up and away from the camera. Here's a shot of my set up:

specular-4

Specular-4

Now, I apologize for the set up shot, because it's missing one key component that you probably picked up on -- the actual light source for illuminating the cleaver. The reason for this is that I ran out of stands so had to hand-hold a reflector in place behind the scene when shooting. Basically what I did was set the timer on my camera, and then held a 48 x 24 inch piece of white foam board above and behind the scene. The SB600 in the right of the above image reflects off the board, which essentially becomes a huge light source that creates the direct reflection in the cleaver blade and brightens the entire scene, resulting in my lede shot for this post. So there you have it, controlling specular highlights to photograph metal objects.

If I were to attempt this again, the one change I'd likely make would be to figure out how to get a direct reflection off of the edge of the cleaver blade as well as its face, but for what I was trying to learn here, I'm happy with my results. Up to this point in this series, I've really only been focusing on some general lighting principles, and not a whole lot on practice. The reason is that when I first started learning to use my flash, I did just start firing away and I eventually stumbled onto to settings that produced acceptable results. However, after going back and learning these basic principles -- apparent light size, light direction, the inverse square law, reflections and specular highlights -- I had a much better understanding of where to start when trying to get a certain feel from my lit photographs. So, that being said, in my next post I'll be going into more of the mechanics involved in flash photography and looking at how to balance flash with ambient light. Hopefully, if you've been reading along, you're feeling more confident in how light behaves and you're ready to move forward with me.


Read all articles in this series:

 

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(4 Votes )

Originally written on November 19, 2012

Last updated on January 24, 2021

User User

1 comment

User on November 21, 2012

Thanks for the interesting and informative article. It's got me thinking about doing some experiments on my own. I look forward to seeing more articles like this. Balancing flash and ambient light is a tricky subject that is still confounding to me.

G