Tungsten-lit daylight

A large part of the “Taking Control of Flash Photography” course that I ran last Sunday was focused on getting to the point where we could quickly, easily, and understandably mix flash and available light to allow us take a mid-afternoon portrait on a sunny day, but with total control over the lighting on our subject.  During the course I went back to first principles in relation to how light works, how flashes work, how cameras and flash communicate, how you can modify light from a flash, and how to control flash and ambient exposures, and it was all aimed at being able to create the sort of portrait that you see above.

The theory took much longer than I anticipated, and so we got to do less practical stuff than I had hoped, but enough to illustrate the key points of the day.  For me, this portrait of Paddy – one of those taking the workshop – brought everything together nicely.  Here’s how we built up the portrait.

The first frame I took, in which I didn’t really care about composition or focus for now, was to establish what the ambient exposure for the background was.  I picked up the camera at whatever setting is was at and took a photo.  This is what I got.

That frame is at f/5.6, 1/250s, ISO 200.  We can see that the background is over-exposed and the subject is underexposed.  Knowing that I could add light later with flash, I set about getting the background exposure correct.  If I did this the other way around and tried to get the subject exposure correct using available light I’d have a very over-exposed background.  If I got the subject exposure correct using flash I’d inevitably have to change everything with the flash as I fixed the background exposure afterwards.  So best to start with the thing you have least control over, and tie that down first.

I was stuck at a maximum shutter speed of 1/250s because (in normal flash operation, at least) my flash and camera won’t sync faster than this.  So I had two controls available to me to lower the background exposure.  I could reduce my ISO (already at 200) or close down my aperture (currently a wide f/5.6).  The Nikon D700 is optimized for ISO 200 (unlike Canon cameras which default to ISO 100) so I left the ISO as is and closed down the aperture two stops to f/11.  This quarters the ambient light hitting the sensor and gives me this:

The background is now reasonably well exposed, but the subject is even more underexposed. That’s ok though – I have a flash and a softbox available to me with which I can throw soft directional light at the subject from an off-camera position (I chose camera right based on the pose Paddy struck naturally at the start of the shoot).

At this stage I needed to think more carefully about my composition, because how I composed would dictate how close or far away I had to put my off-camera-flash-in-a-softbox in order to keep it out of the frame.  For soft light I want it as close as possible, so I’m aiming to have it just out of frame at camera right.

I chose a 70mm focal length to give me a tighter crop, and allow that softbox to come in close, and I took a stab at 1/8th power (I think – I can’t recall for sure, but the absolute number isn’t particularly important) for the flash power.  Everything else stays the same, so this shot is still f/11, 1/250s, ISO 200:

Now if for some reason my shoot had to end right at that instant, I could probably live with that photo.  But I had a little bit of time, and wanted to do better.

The main thing that was niggling at me from that frame was that the light grey wall in the background was distracting, even though it was no longer over-exposed.  In fact its exposure was bang on.  So I decided to drop it’s exposure down about a stop.  Again to do this I could lower the ISO or close down the aperture – the shutter speed couldn’t help me here – so I went from f/11 to f/16.

This time though I have to compensate with the flash power,  because 1/8th power at f/16 is going to let half as much light into the sensor from the subject as 1/8th power at f/11.  So I increased the flash power to 1/4.  Now everything is as it was, except the background is a stop darker, and so the subject should stand out more.  And he does…

We’re still not done yet though, although this is an even more usable picture than the last one.

There’s a lack of colour in the scene, which is exacerbated by the fact that Paddy’s shirt is similar in tone to the background.  I can’t ask him to change his shirt, but I can do something to add a bit of colour contrast between him and the background.

The first step is to leave everything as is, but to add a CTO gel to the flash.  That throws orange light (it’s actually balanced to tungsten) on Paddy, leaving the background to be lit by daylight.  That gives me an image which looks like this:

I think you’ll agree he’s too orange.  It looks like fake tan gone bad.  But I’m not planning on leaving it like this.  Because Paddy is now primarily being lit by a tungsten-gelled flash, I change the white balance of my camera to tungsten.  That will bring him back to the correct colour temperature and give me natural skin tones in my image.  But the background is being lit entirely by daylight, which is cooler than tungsten, so when I shift my white balance to tungsten, the background goes blue.  This is the effect I’m after, because now I have my colour contrast and Paddy stands out from the background.

Here’s the final shot again (repeated from the top of this post).

Below is a setup shot for this portrait, courtesy of Paul Timon who was on the course.  Looking at these two shots together there are a few things to note.

Firstly, in the background you can see the shadow of some sort of fixture on the wall at top left. That shadow is hard, and is from the sun high in the sky, so we can tell that the background is being lit by hard light from that direct sun.

Also, the key to getting this portrait to work is that Paddy is entirely in the shade – as you can see from the setup shot – and if he wasn’t I wouldn’t have enough power in my flash to create the same picture.  Plus I wouldn’t be able to control the exposure on him independently from that in the background.

I triggered the softbox flash from the flash on the top of my camera, angling it so that it was pointed towards the receiver on the off-camera flash.  Outdoors this is important more so than indoors, where the trigger signal (IR) bounces around much more.  I also oriented the off-camera flash head so that the receiver window was facing my camera.  My on-camera flash isn’t adding light to the scene though – just acting as a trigger.  I could have done this shot using a PC cord, and ebay trigger,  a TTL cord or a Pocketwizard just as easily.