Wednesday, August 08, 2007

Lighting: specular highlights

Lit from aboveThis time around I'm playing with controlling the specular highlights that appear on the subject. The specular highlight is the reflection of the actual light source, bouncing off whatever it is you are lighting - in this case it is the white glare or sheen you can see on the pepper mill and also the white reflection on the metal top. Some subjects (such as metal) really only show specular highlights and no diffuse reflections, other's like wood, show a mix of specular and diffuse highlights. These properties of the materials can be used to control the lighting in a variety of interesting ways. I'm also using some of the other tricks from previous lessons to control diffusion and fall off, along with playing with the location and size of the specular highlight. From left to right, the shots are: (1) Bare flash to camera left, at the same height as the pepper mill, about a 45 degree angle. Nasty light, harsh dark shadow, bright, narrow specular highlight the length of the mill because the light source is small and non-diffuse. To try and improve the situation (2) I moved the light source to almost directly overhead, but still slightly to the left to give some direction. You can tell this by where the shadow falls on the pepper mill. Now the table is better lit but the shadows are still harsh. The specular highlight has moved to the curved edge of the top of the pepper mill, as this is the direct reflection of the light. There's no specular highlight visible from the table, as the angle of the light, camera and table means it isn't visible. In shot (3) I've added a diffuser between the flash and subject. The specular highlight has gotten a bit bigger, as it is now reflecting the diffuser. The shadow edges have softened, both on the table and along the edge of the mill. In shot (4) I added a small white reflector to the right of the camera to bounce some light back in to fill the shadows. This doesn't change the specular highlight from the light source, but adds a new specular highlight on the right, which is the reflection of this new light 'source' - the bounce card. You can see that new highlight particularly in the metal top of the mill. In the final shot (5) I changed the light source from a diffused flash to a flash bounced into a silver umbrella. You can see that the specular highlight has become larger again, reflecting (literally!) the change in size of the light source.
Side highlightIn this sequence, I've gone back to the original light position, at the same level as the object, at about 45 degrees to the camera access. The goal this time was to create a specular highlight that ran the height of the mill. I brought the light in closer to get more fall-off on the background and diffused it to control how harsh the specular highlight was. The second shot, in the middle, brings in a bounce card to the camera right, again to fill in the shadows. Once again, these changes can be reverse engineered by looking at the specular highlights in the metal top of the mill. Finally after inspecting the shot on the LCD, I decided I wanted to get a bit more definition on the metal top and background, so I moved the light source a bit further away to decrease the light fall-off towards the back of the scene. That added some more light to the background, at the top of the shot which brings the top of the mill out of the darkness. Note that moving the light also reduces the effective size of the light to the subject - so the shadows in the third shot become that bit more defined.


Kavey said...

I'm too much of a candid girl (read lazy) and have never really got into using a flash much. But these shared exercises have really helped me visualise what one can do with just a single off-board flash and a reflector/ diffuser. Very helpful - please don't delete them!
What are you using to diffuse your light?

Gordon said...

I have a couple of those pop-up diffusers (metal frame, with a diffusion panel)

I also made some from some mat board, cut with a normal window mat, and then taped tracing paper over the gap. Works really well - solid enough to hold up because of the mat board and cheap to replace if you tear it - just stick another sheet on.

I made a few reversible reflector boards from black poster board (which is white on the back) That gives a good reversible bounce card - as the black side can be used to kill reflections too.