Have you ever struggled with high contrast situations? Perhaps you’ve encountered shadows so dark or big that they steal the attention from the subject? That’s because sometimes you need to add a second light to your images. However, if they are different types of light, it can be difficult. Keep reading for a beginners guide on how to expose when you’re mixing flash and continuous lights.
Taking a photograph means to capture and register the light, so understanding how to do that is key to obtaining a good result. In this tutorial, I want to talk about continuous light and flash lighting, and how you can set your exposure to register both. First, I’ll explain what I mean by these terms.
Types of lighting
Continuous light (also called constant light) is the light that is on for the entire duration of the photo. This can be natural light when you’re outside, but can also be window light when you are inside. It can also be artificial light such as a table lamp or even professional photography lighting. Basically, it ranges from the sun to a candle – as long as it is continuous.
Then there is flash lighting, which is only available for a quick moment when triggered. It can be from a professional strobe light, an off-camera flash, or the flash integrated into your camera. You can use these two different lights exclusively or together to complement your lighting. You can use them to create a special ambience or to achieve a particular effect. In this tutorial, I’ll explain how you can set your exposure when you use both continuous and flash lighting in the same shot.
Mixing the lighting styles together
I want to show you a situation in which I used continuous natural light as the main light and then filled in the shadows with an off-camera flash.
Photography is about representing our tridimensional world in bidimensional ways. To do this, we make use of different things. One of them is shadows because they give depth. So we don’t want to eliminate all of the shadows – we want to control how many there are, how dark they look and their direction. If I slow the shutter speed to let in more light and try to ‘fill in’ the dark shadows to soften them, it overexposes the main subject.
Therefore, it needs another source of light from the right. You can add this light source using either another continuous light or with a flash. I did this image with ISO 200, f/8, 0.3 seconds – the same settings I used for the correct exposure using only the continuous light. This solved the problem of one set of shadows but ended up creating new ones on the opposite side, so I need to fix the exposure again.
Since the flash is just a shot of light that lasts for a fraction of a second, it doesn’t make a difference how long your shutter speed is open like it does when shooting with continuous light. You can set your shutter speed as slow as you want or as fast as the synchronization limit allows you (in my case is 1/250 sec). The flash lighting exposure needs to be regulated by the aperture.
If you set the shutter speed to the light coming in from the left, meaning the continuous sunlight coming from the window, and set the aperture according to the light coming from the flash on the right side, you can control the complete illumination of the scene.
You can decide which shadows are good to keep and which ones to fill and by how much. In summary, have an image with depth and enough information both in the highlights and the shadows to either keep as shot or post-produce to your liking.
As you may have noticed on the examples, every light has a different color temperature, that’s why some photos have warmer or colder tones. This is a broad topic that I can’t manage to cover in this one article, but I did want to mention it. When you’re mixing different types of lighting you may need to deal with this. Sometimes the auto-white balance of the camera does a good enough job. However, if it doesn’t, I advise you to do some more research about it.