balancing flash and ambient exposure
This topic – balancing flash and ambient exposure – seems to one that many newer photographers struggle with. The big hurdle seems to be the basic starting point – how do you decide on the exposure for each?
I’d like to explore this topic a bit with this post. The trigger for this was a question that someone emailed me regarding an image in my book on flash photography. Instead of answering the question directly, I thought that a wider answer might be more illuminating. We’re still on that perpetual quest for more aha! moments. So let’s see where we head with this. (I’ll come back to the specific question and answer at the end of this.)
But why do we even want to add flash to a subject when the available light is soft?
The answer is that with flash we can control the direction and quality of light, and create a more dynamic image.
We don’t necessarily just use flash to avoid camera shake and / or poor exposure in low light. We use flash to create better light on our subject. We can ‘clean up’ the light that falls on our subject. Or to create more dynamic and interesting light. It’s about control. We decide. So where do we start?
The simplest approach for me, when I work in fairly flat and even ambient light, is to under-expose the ambient light by a certain amount. Then we add flash for correct exposure. So how much do we under-expose the ambient light by? Well, it depends. Usually a stop is good. Two stops can also work. If you’ve seen some of the images in fashion and music magazines where the subject is in a pool of light .. yet, the sunlit cityscape is darker, then that is because the photographer under-exposed the ambient light by 2-3 stops. Even in bright sunlight. So we have some leeway. That should ease some of the anxiety.
Under-exposing the ambient light by a stop, and then adding flash … is but one scenario, and one recipe. This approach won’t apply to every possible situation you might encounter .. but it’s a good starting point in grasping that Big Question – where do we even start in balancing flash and ambient light?
Let’s start of with an example where the previous method wouldn’t work:
settings: 1/125 @ f3.5 @ 800 ISO
lighting: Q-flash T5D-R, in TTL mode diffused by medium softbox to the right
(A speedlight in the softbox would’ve worked just as well here.)
Here’s the image without flash, just so we have a reference ..