Sweet and Easy Flash Exposure

JohnsonDoug_Flash PowderBalancing ambient and flash exposure in photography has perplexed humankind since its beginnings when flash powder (yikes!) was used to light things up in the early 1800s. These early pioneers had to rely on intimate knowledge of manual flash exposure to get things right.






 – ©BlitzlichPulverPhotography

With recent advances in technology like “Through The Lens” metering (TTL)  and onboard flash unit navigation for both TTL and manual flash exposure, it’s become relatively easy peezy to get sweet results.

We still possess all the power to control the flash output manually and I’ll discuss this later in this discussion, but with TTL mode technology, the flash and camera work intelligently together to balance the ambient and flash exposure for you. Whether you’re using the little pop up flash on the camera or more powerful models that fit in the hot-shoe, it’s good exposure made simple. If you’re a Canon or Nikon shooter, these hot-shoe flash units are affectionately known as Speedlites (Canon) or Speedlights (Nikon). A fun thing about the technology is now we don’t have to relish (pun intended) in front lighting our subjects the way onboard camera flashes do… we can now move our flashes off camera, still get great exposure results and produce much more dynamic light… fantastic!

I know what your thinking… if TTL technology is so amazing, why would we even consider manual flash exposure? Here’s some food for thought and why you might choose one over the other.

Our camera’s auto exposure modes; Program, Aperture, and Shutter priorities attempt to create good exposures by juggling our camera controls and do so very well most of the time. Well, the TTL technology compliments the camera system by working to balance the ambient exposure you create with the flash exposure automatically and it also does a fantastic job “most” of the time… and since the TTL system is attempting to balance both, we should think about the flash as a fill light.

Here’s a few variables that influence (positively or negatively) the TTL exposure as it attempts to balance the two exposures:

– subject reflectivity
– volume of the frame the subject occupies
– subject to background distance
– subject position within the frame
– available light
– strength of the backlighting
– camera exposure algorithms

The photographer has some influence on the outcome, but remember, ultimately the TTL system has the final say.

In manual flash mode the two exposures rest squarely on your shoulders. Just like manual exposure mode with the camera controls… meaning, you are the commander of both (ambient and flash). Like the flash pioneers I mentioned earlier, being proficient requires knowing a thing or two about Guide Numbers (flash power), the inverse square law and “The Rule” – “shutter speed has no affect on the flash exposure”. It’s not that difficult once you understand a few basic concepts of light and flash. Manual flash is also a bit more powerful at full power (1/1) than anything TTL can dish out.

There is this little helpful app (understatement of the century) we can now use to calculate manual flash power wherever we might be with our smart phones and that’s PhotoCalc by Adair Systems LLC. Here’s a screenshot and the icon to look for when buying.









So, now let’s discuss a simple workflow to maximize our results and we can simplify the process by thinking about and accounting for the two events (ambient and flash) that happen during the overall exposure.

In TTL Flash Mode                                           TTL Exp Mode1
JohnsonDoug_TTL Exp ModeJohnsonDoug_TTL Exp Mode1







1. Meter for the ambient exposure you want (brightness) and set it.
2. Use flash exposure compensation (FEC+/-) to create the flash exposure for your subject

In Manual Flash Mode
JohnsonDoug_Manual Exp Mode







1. Meter for the ambient exposure you want (brightness) and set it.
2. Use flash power, the inverse square law (flash to subject distance), aperture and or ISO to compensate the flash exposure for your subject.

Before you grab the camera and head out the door, keep these other little keepsakes in mind when your working:

1. The camera’s sync speed when metering. It’s the fastest shutter speed the camera will allow when a flash is used. For most cameras it’s around 1/200s
2. Smaller apertures have a profound negative affect on flash exposure.
3. In manual flash mode – “Shutter speed doesn’t affect the flash exposure” – So, think about it like this : use shutter to compensate for the ambient exposure and use aperture to compensate for the flash exposure. It’s helpful to remember this acronym: SAAF (Shutter – Ambient, Aperture – Flash).
4. Know and study your histogram on the camera… it is your 21st century light meter.

*Don’t forget the fresh batteries, bring your creativity and some flash filled fun friends and you’ll be a happy little speedliter or lighter.