Infobits: Normal and Slow Sync Flash

In the aftermath of a failed UP night shoot last night (how redundant), I decided to fiddle around my cam while reading Ken’s User Guide in the hopes of learning something new.

After around 5 minutes of endless browsing, I came across a topic I rarely delve into – flash. Well, it’s about time I got to know a tad about it anyways since I get to use it every now and then without really knowing what it does. So for the first time, I got to grasp the difference between Normal and Slow Sync Flash and how it affects the exposure. Or at least that’s what I’d like to think

Normal Flash
In Normal flash, the flash fires instantly after the shutter is released. My friends call this the “blinding mechanism”.

In P(rogram) and A(perture) modes, it also normally tells the shutter to stay open no longer than around 1/60 seconds (according to Ken and which I was able to validate last night).

1/60 seconds is relatively short so usually you may notice that indoor pictures taken with Normal flash produce a brightly exposed subject but with a substantially underexposed (near black) background.

The dark background is due to not having a long enough shutter to let enough ambient light fill the background.

The bright subject on the other hand, is caused by too much direct light hitting the face. On people with make-up, it’s as if too much face powder was put on. Might as well used a cheapo flashlight if you really intended to have this effect. This is where flash diffusers or bouncers come in very handy because they diffuse or soften the intense light hitting the subject (thus also minimizing harsh shadows) and/or bounce the light off, say the 10-foot ceiling, to create incident light (which is softer on the skin) and adequately light the background as well.

On bright sunny days especially when you have no choice but to have the sun behind your subject to capture the breathtaking backdrop, you can also use Normal Flash to provide fill light to an otherwise shadowed out subject. I use this a lot.


Slow Flash
Slow Flash on the other hand, which is only available in P(rogram) and A(perture) modes, lets the shutter stay open long enough to let ambient light expose properly with the flash. This creates a very well exposed image since both the subject and background are well lit – the subject is lighted by the flash while the background is illuminated by ambient light (and the flash as well) due to the longer shutter. The trade-off though of the longer exposure is that moving subjects are blurred and in very dark rooms, the shutter can be awkwardly very long for people as subjects.

The rule of thumb for capturing sharp pictures with no blur is to use a shutter speed of 1 over the focal length (1/f). With the kit lens at say 50mm focal length, the ideal shutter speed would be somewhere around 1/50 seconds. Note however too that it may be hard to avoid blurs while taking hand-held shots at shutter speeds slower than 1/50 seconds, especially if you’re “pasmado” like me. If you have Vibration Reduction (VR) lenses like the Nikon 18-200mm VRII or the 55-200mm VR, you could lower this minimum to around 2 to 4 more stops. Otherwise, a tripod is a must if you want to use Slow Flash in inadequately lit rooms.

In daylight, Slow Flash would presumably have the same effect as Normal Flash since the required shutter would be relatively short anyways.

Slow Flash ain’t available in M(anual) mode since you can adjust the shutter speed as desired. But it gets tricky since it would be hard for newbies like us to estimate how long it would really take to have a well-exposed image with flash. It comes with experience. So I guess this reason is enough for me slowly shift away from M(anual) and start familiarizing myself with P(rogram) mode now.

Test Shots
Both shots were taken at 18mm focal length using P(rogram) mode at P* f/3.5 under ISO200. I used a tripod as well to maintain the same framing and counter my unsteady hands.

Normal Flash (1/60s) Slow Sync (2s)











Keep on shooting!