Flash-lit Friday: Birthday cake

If you visited here yesterday, or have been playing really close attention, you’ll know that my blog is celebrating its first birthday today, and what better way to celebrate than with cake?   In this case, a cup cake.  Just the one, but then the blog is just a toddler.  And if you’re going to have cake, you might as well photograph it before you eat it, right?.  Read on for a breakdown of the lighting (all battery-powered strobes) that I used for this photo.

I photographed this, as I tend to do for these “flash-lit Friday” photos, well past sunset in the kitchen of my house – well, on the kitchen floor actually – so the light is all artificial.   My starting point is to check that at my desired aperture and at the maximum shutter speed that I can sync flash – 1/250th of a second on my Nikon camera – that there will be no contribution to the exposure from any lights that are turned on in the kitchen.  What’s my desired aperture I hear you ask – well for this shot I want to keep some detail, and I’m zoomed in on a small object not too far away, so f/8 sounds reasonable.  Any narrower and any blemishes on my backdrop (more on that in a second) might show up.  Any wider and I’ll have too little depth of field.

Aside: as it turns out, I should have tried f/11 or even f/16 – the front of the cake is not as sharp as I’d have liked. But you’ll forgive me that mistake on the day that is in it!

The numbers don’t really matter here to be honest – the point is that my starting exposure is at an aperture that suits my needs, and the shutter speed is bounded by being slow enough that my camera can sync with the flash (a constant for every camera) and fast enough that it kills all the ambient light.

A test frame shows that all the ambient light is removed from the exposure at f/8, 1/250s, ISO 200 (ISO was chosen to be low, unless I find I need to up it later).  I’d show you the test frame, but just imagine a black rectangle about so big.

So next I set about lighting my subject.  I place it in my floor-based mini studio, which comprises an A1 sheet of off-white card (usually used to cut mounts and backing boards from), curved to give me a seamless backdrop.  On top of the card I put the glass from a frame, to give me a nice reflection of the cupcake to anchor the frame, and keep it from appearing to float in mid air.

The subject is going to be lit with two lights – sort of a main light and a fill light, but the two lights are set up in similar ways.  Both are diffused, and placed either side of the subject, level with it.  The main light is on camera left, and at a 60 degree angle to the subject.  It is diffused, cheaply, by a folded sheet of A4 paper, which softens the light nicely without needing to use an umbrella or softbox.  I start at a power setting of 1/16, and end up at 1/32 as it’s nice and close.  The effect of the light is as follows:

The fill light, or arguably, the “other” main light, is similarly diffused at camera right, but the angle is about 30 degrees so that it’s pointing more towards the backdrop than to the subject.  In this way it is feathered, and will do two jobs – firstly it will give me sidelight at the right hand side of the subject – softened by the paper, and secondly it will give hard, direct light on the right hand side of the backdrop.  It does the job of two lights.  Firing alone it looks like this:

It’s also at 1/32 power for a simple reason – both it and the main light are SB-600s and I have them on the same channel in CLS so they have to fire with the same power.

When using CLS via the pop-up flash I can control two groups of flashes.  It’s most important for me to be able to independently control the background light, so the other two are forced onto the same group.  Same flash, same power, but feathering one gives a slight (but barely noticeable) ratio between the two.  Had I wanted more of a ratio I could have moved one further back from the subject, or the other closer.  There are always variables beyond power that you can use when lighting like this.

With both lights firing together, I’m getting close to a usable photograph:

I’d like to even out that background and I have a third flash (an SB-800) just to do that.   I position it at camera left, just in front of the backdrop and pointing across it.  I deliberately allow some light to spill on the cake, as it will give a nice rim light on the left-hand side to define the edge.  I end up with 1/20th power to give me the white background I desire and that spilling of light works well:

For this final image I cloned in an unlit candle tip from an earlier shot.  I had hoped to succeed in capturing a lit candle, but should have checked the exposure for that at the start of the process, because when I lit the candle in time for the final frame, it was not showing up in the final exposure.  I tried to merge it in, unsuccessfully, but in reality should have used the flame for my base exposure and built from there for this effect.  By the time I realised this, I wasn’t much in the mood to start adjusting flash powers, and so left it unlit in the final image.

All that remains is a pull back shot to show how a sheet of A1 card, two A4 sheets of paper, and three off-camera flashes can help to create a mini studio perfect for this type of shot.

Have you tried something similar?  Do you have comments or criticisms on my shot?  I’d love to hear them!