Balancing Ambient Light with Flash.

[jwbryson1]

In Neil van Niekerk's book "Off Camera Flash" (pages 56-57 for those playing along at home), he describes balancing ambient light with flash. In this particular image, he intentionally overexposed the background by 2/3 of a stop to have the background be slightly brighter than his model. He then added a small bit of fill flash "to open up the shadows on her face."

Question: If the model is in the ambient light, and the ambient light is being intentionally OVERexposed by 2/3 of a stop, won't adding fill flash on the model OVERexpose her by that much more?

This is confusing to me. :scratch: I am thinking of it like this: Assume that you shine a flashlight at an object and the object is very bright, brighter than necessary in fact to see it clearly. So in order to see it better, you shine a SECOND flash light at the object. Am I thinking of this wrong?

 

[Big Mike]

I don't have the book...but I can envision the scenario.

Keep in mind that 'ambient light' doesn't mean even lighting. The background could well be brighter than the model to start with, or maybe the position direction of the model, leaves some or all of her face/front, it shadow (or at least a bit darker than the rest of the scene that the camera could see).

So in this case, it sounds like he's metering for the background, then over exposing that....then evaluating the foreground/model, and deciding to add flash for fill.

Your inclination is correct is that light is additive. So if you add light to a scene, it will add light to both the shadows and the highlights that it hits.
But if the main source of light is off-camera and directional (so you can see both shadows and highlights), then by adding light evenly (the base form of fill light), you will start to even out the ratio.

 

[MReid]

I am with you....I gave up on trying to figure it out technically a long time ago, now I just eyeball it.

I shoot in Aperture priority.
I take a test shot, see how the mix looks, adjust the power on the flash (ttl). As I increase the power on the flash the background will darken and vice versa. Of course I always only use 1 flash so this is easy to do.

Once I reach a good mix I then adjust using the exposure compensation tool for the overall exposure of the shot.
Usually takes a shot or two to get the mix right, then I am good until I move to another lighting condition, repeat the process.
Fast and easy....works for me.

 

[jwbryson1]

So in this case, it sounds like he's metering for the background, then over exposing that....then evaluating the foreground/model, and deciding to add flash for fill.

Exactly what he's doing.

But if the main source of light is off-camera and directional (so you can see both shadows and highlights), then by adding light evenly (the base form of fill light), you will start to even out the ratio.

This makes some sense to me. I need to experiment with this myself to get a better feel for it. Thanks for the post.

 

[gsgary]

When mixing ambient and flash your basically have 2 exposures, shutter speed controls ambient and aperture controls flash so it is always better to shoot in manual, What i do is take an ambient say F8, 1/100, iso100 if i want the background to be over exposed i will have a flash reading of F8 1/200 iso100 but shoot at F8 1/100 iso100, easiest way is to match ambient and flash with a shutter speed of about 1/125 to make the background darker increase your shutter speed if you want it lighter decrease shutter speed. I hope that makes sense

 

[jwbryson1]

When mixing ambient and flash your basically have 2 exposures, shutter speed controls ambient and aperture controls flash so it is always better to shoot in manual, What i do is take an ambient say F8, 1/100, iso100 if i want the background to be over exposed i will have a flash reading of F8 1/200 iso100 but shoot at F8 1/100 iso100, easiest way is to match ambient and flash with a shutter speed of about 1/125 to make the background darker increase your shutter speed if you want it lighter decrease shutter speed. I hope that makes sense

It does. Good post. Thanks.

 

[Robin Usagani]

His book probably has photos to explain it. This particular case, the background is probably bright and the subject is darker.

 

[2WheelPhoto]

I'm trying to grasp the concept myself. In these pics a super bright background I tamed with a fast shutter and then the hot fill with OCF.