Lighting a lens with a graduated specular reflection

Lighting a lens with a graduated specular reflection

Lighting a lens with a graduated specular reflection


In this series of basic tutorials, we take a simple technique and then build on it.

First, we introduced diffused specular reflections in this post. Diffused specular highlights (or reflections)  are reflections of the light source that we can see through, to the subject below. It’s a simple technique that is used whenever we photography shiny subjects.

Then we moved on to a subject with more complex shapes and more complex lighting needs, a camera. Again, it’s a shiny subject that needs soft diffused lighting to avoid glare, but it also needs harder lighting that draws the eye to the contours, and defines the shape of the subject.

But the hard accent lighting that’s needed also brings its own problems, in particular it creates hard and pretty uncontrolled lighting on the lens, and that’s the problem that we’re going to deal with in this tutorial.

Here, it’s a camera lens, but it can be any kind of convex bit of glass, as you will see in a future tutorial if you subscribe to our blog.

There’s nothing especially difficult about lenses, but the convex shape, and especially on a wide angle lens like the one featured here, demands a much larger light source than a flat surface needs. The problem, as you can see below left in this close up  shot, is that the light isn’t flattering to the lens. and so we need to step outside our comfort zone as far as equipment goes, and use a special tool that isn’t found in most studios – but don’t worry, it isn’t an expensive tool!

The tool we use is called a silk.  A silk is a large sheet of diffusing material, different materials produce slightly different effects, but pretty well any of the options will do the job.

I went out and bought a 2 x 2 metre plain white shower curtain from Wickes DIY for this shot, it cost £9.99 – which sounds good, except that the last one I bought from them only cost £3 something… It’s possible to buy ready made silks, and they have the advantage that they fold up small and are held taut, but they cost a lot more than £9.99…

You could also use ripstop nylon if you have it, that’s the material used for softbox diffusers, or you could use an ordinary white bedsheet. It doesn’t matter. What we cannot use is a softbox, even if we have one that’s big enough. The reason for this is that softboxes are illuminated evenly (or at least the decent ones are) and we don’t want that, we want to graduate the light so that the reflection is also graduated.

A silk can be partially lit so that the light intensity falls off from the centre out to the edges and is ideal for creating graduated specular highlights, or we can graduate it in other ways, to taste.

In creating this effect in the studio I had to position the silk within 2 ft from the subject lens because the surface of the lens was convex and reflected light from all directions. In fact, as this is a wideangle lens it’s about as convex, and as difficult to light, as it gets.

You can use any type of light and any modifier on that light to light the silk, which will be reflected in the surface of the subject. You can light the silk with a large diffused source or a small projected source, a softbox, bare reflector, or just about anything else to project any shape and edge softness of the light onto the silk which will then reflect as a graduated specular highlight in the subject.

The silk needs to be taut, so the first job is to fix it to a piece of wood, the weight and straight line will hold it straight. I fixed the top to a boom arm, partly because I have one and partly because a boom arm makes it a bit easier, but you can manage without one.

The next job is to arrange the silk directly in front of the subject, as close to it as humanly possible but leaving just about enough room to position the camera you’re using to take the shot – obvious but not always easy to do – controlling the camera remotely from a laptop helps.

Then you light the silk, unevenly. My usual starting point is to either use a small light source, for example a standard reflector, to light just a fairly small central area of the silk. This creates a bright central area, fading off towards the edges, but it’s no good on such a convex shape so for this, it’s a better bet to light the whole of the silk with something like a softbox, and to then add the uneven lighting by adding a second light at a higher power setting.

The second light can be literally anything, in the photo above it was a standard reflector with a gel over the light, as you can see. The colour isn’t accurate but unless you’re taking the shot with the intention of selling the subject you can be as creative as you like.

Don’t like the orange look? Fine, how about blue then? Or no colour at all, or a different colour? The whole point is that the light on the lens is graduated, so you can have, for example, both blue and white light in the same shot. That wouldn’t work with anything other than a silk lit unevenly, and although it can all be done in Photoshop, that’s a hard work way of going about it.

 

Of course, you can get a lot of different effects, just by varying the brightness and the position of the second light. I often add a strip sofbox near the top of the silk, to produce a slightly brighter area at the top of the lens, but you really need to experiment for yourself and see what you can do with whatever lighting tools that you have available.

Back in the ‘Good old days’ when everything was shot on film, photographers knew these techniques and used them on shots of this type, but if you look at photos of lenses and cameras on manufacturer’s sites you’ll see that the photos are often lit very badly – even though all that they need to do is to use this technique and add it to their photos on computer, which is much easier than the ‘old’ method used when shooting on film, because when there is no editing we need to light the rest of the shot too, and also mask off the areas of the subject that we don’t want the silk to light – with digital, we can get the same result more easily.

As always with my tutorials, I’ve concentrated on the lighting and not on computer work, but careful computer work does need to be added for a good finished result.

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