Adding Light: Mixing Flash with Daylight

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High Speed Sync flash with Canon Speedlite

While most of the photos in my most recent portrait shoot were taken in natural light (you can see them here) I took the opportunity to try out a technique that combines daylight and flash. You can see the result above. Look closely and you’ll see that the light on the rocks on the right hand side has a blue cast. So does some of the light on Wimmy’s hair.

Here is a photo taken in natural light so you can see the difference. The light is softer and there is no shadow under her nose:

High Speed Sync flash with Canon Speedlite

Here’s how I did it.

I set the camera to manual mode and used a setting that underexposed the image by around 2 and a half stops. The exposure settings were ISO 100, f2.8, 1/500 second. I selected f2.8 as a wide aperture means the flash doesn’t have to work so hard to light the subject (the smaller the aperture the more flash power required). This is the result:

High Speed Sync flash with Canon Speedlite

The ambient light was very bright, even in the shade, so that meant that a shutter speed of 1/500 was required. To counter this I set my Speedlite to HSS (High Speed Sync) mode. This lets the Speedlite operate with shutter speeds greater than my camera’s sync speed of 1/200 second. The only downside of HSS is that the Speedlite consumes over double the power so the batteries run down quicker.

I covered the head of the Speedlite with a Honl CTO gel. This alters the colour of the light emitted from the Speedlite from daylight balanced to warm orange. The colour approximates what you would get from a torch with a tungsten bulb:

High Speed Sync flash with Canon Speedlite

I fitted my Speedlite with a Lastolite Ezybox Speedlite. This is a small softbox that softens the light from the Speedlite so that it is more flattering. The light from a bare Speedlite is too harsh for portraits:

High Speed Sync flash with Canon Speedlite

I connected my Speedlite to my camera with an Off-Camera Flash Cord. You can buy the Canon OC-E3 or a cheaper third-party model. I use the Jessops cord.

The Off-Camera Flash Cord lets me hold my camera in one hand, and a Speedlite in the other. It is ideal when the Speedlite is positioned close to the camera. It retains all communication between the camera and the flash unit, and lets me control the Speedlite from the camera using the Flash Control menu. This is available on all EOS cameras since the EOS 40D, and much easier to use than adjusting the controls on the back of the Speedlite.

I set the Speedlite to automatic, held the camera in my right hand, the Speedlite in my left (with the softbox pointing at Wimmy) and took a test photo. I checked the histogram and the exposure was almost perfect the first time. If Wimmy was under- or over-exposed I could have altered the power of the Speedlite using the flash exposure compensation function.

Post-processing

I processed the images in Lightroom. Here is the initial result, with the colour temperature set to daylight so that you can see the effect of using a CTO gel on the Speedlite. It look as if Wimmy has been lit by a torch or lamp rather than by flash:

High Speed Sync flash with Canon Speedlite

The image was a bit dark so I brightened it:

High Speed Sync flash with Canon Speedlite

Finally I adjusted the colour temperature from 5500K to 4308K. This effectively applies a blue colour cast to the entire image. The area lit by the Speedlite now looks warm, rather than orange. The areas lit by ambient light (rocks on right and hair) now look blue.

The setting of 4308K is subjective – I just moved the colour temperature slider until it looked ‘right’.

Here is the final image again:

High Speed Sync flash with Canon Speedlite

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« Understanding Lenses: Part II – A Guide to Canon Normal & Telephoto Lenses |  Lenses I Own »

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