If you check out our Getting Flash tutorials,at one point whilst talking about controlling your shutter speed to change the lightness or darkness of the background, I mention briefly that you have to be careful shooting at the slower shutter speeds, i.e. from around a 1/60th of a second down over. This is because of an issue caused by secondary blurring. As the flash fires at an extremely short duration often as short as 1/10,000 of a second,and as the whole duration of the cameras shutter cycle is a much longer period then there is a danger of a sort of double exposure effect. This is more apparent the slower the shutter speed that you use.
Like most things photographic though, a fault can be used to positive effect.
Commonly known as a “twirl” in underwater photographic circles this effect can be used to liven up a fairly static subject.
With a camera that you can control manually all you do is choose a lengthy shutter speed, I find that around a 1/15th to a 1/4 of a second works well, and the slower the shutter speed the more pronounced the effect.
You will have to be mindful of the background exposure and if its fairly bright this may mean a very small corresponding aperture, i.e. f11 through to f22, which will mean that your strobes will most likely need to be cranked up to the max. It’s for this reason that I usually do these shots, late or early in the day when its generally more gloomy.
I usually do a test exposure on my hand held in front of the dome port to see if the flash output is enough, and when happy things are looking good I find a subject.
When firing off your shot its worth pointing out that most modern cameras these days can allow you to define whether or not the flash is triggered at the beginning or end of the shutter cycle, by default they are normally set to fire at the start, which is called “first curtain synch” and you can usually choose the option of “second curtain synch” For this type of shot It doesn’t matter much, but is worth experimenting with so as to see what is going on.
Whilst firing all you do is give the camera a bit of a twist around the axis of the lens, and it is this which creates the dynamic secondary blurring, with everything illuminated by the flash in your foreground hopefully nice and sharp.
It works well with shots of your fellow divers and can give a bit of dynamic oomph and movement to the shot.
The picture above and the one below of our photo workshoppers I took out in the Maldives recently.
And below that a more exaggerated example of a videographer friend of mine.
The shot above for less of a spin effect I have used a faster shutter speed of 1/30th second so the spin is more subtle.
My friend GeGe the videographer above was shot with a slower shutter speed of 1/4 of a second exagerrating the spin effect.Also with pictures of people I think its betterk to make sure you have some eye contact.
And don’t give up if it doesn’t work first time try adjusting your shutter speed aperture combo,and changing the speed of your spin until it looks how you want it.
“Can this be done with a compact fully automatic camera?”
In most cases quite easily, even though with loads of point and shoots you don’t have any form of control over your aperture and shutter speeds. You will often find that you can set the flash to what is called “slow speed synchro” this is usually in the flash menu with a symbol of the lightning bolt of the flash alongside a condle or some other symbol denoting low light. Or you may find you need to switch it on in the main menu settings. If you’re not sure email me and I will get back to you, with an answer.
This shot below I took with an eight year old digital compact camera with no other accessories at all and only used the built in flash.
“Can I fake it in my photo editing software?”
If you have a basic knowledge of working with layers you can fake it quite easily using a similar technique to a blogpost I did a while back about how to get rid of backscatter in your pics.
The pair of pictures below shows a before and after result where I have exaggerated the effect within Lightroom and Photoshop, this was a variation on a twirl where instead of twisting the camera I moved it from side to side when exposing the shot, giving the diver a sense of speed and motion through the water.I felt it needed more oomph so I pushed the effect a bit in software.
Here is a video I have done, showing this in practice, for speed I have kept the info and narration to a minimum, but for a fuller explanation check out the earlier blogpost.
Faking it can have mixed results you can go all out and make it obvious you have used digital manipulation, or be more subtle and more realistic, it’s entirely up to you, there are no rules, other than having fun.Like all effects though it’s a useful thing to learn but don’t overdo it. Motion blur is very easy so why not give it a try yourself?