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Using flash to freeze action and 2nd curtain sync

There are two main use of flash, first fill flash to balance ambient light and second flash for freezing action.  This article focuses on using flash in freezing action. 

Why do I write this article?  I write this article for helping less experienced photographer who can't use flash properly and not intending to take any photography class.

In order to preserve the ambient light, the camera will use long shutter time.  In action where subject moves, the subject will off course be blurry and invisible.  On this aspect is where the flash come to help.  See the image below for example.

Therefore flash is needed to freeze the action.  Flash produces light that is much stronger than the ambient light.  This light will be bounced by the subject.  Then the light will enter the camera the as strong light, much stronger than the ambient light.  Therefore making the subject visible and frozen.  Flash will help to freeze the moving subject.

However Improper use of flash will result in ruined image.  Without mastering flash, you will hate flash.  I used to hate flash, due to my lack of skill.  I used to made super bright face with overly dark background.  Please see the example below

On this picture below, the amount of ambient light is the same with the image above.  For compact camera using slow flash synchronisation is the cure.  The camera will fire flash then wait until the ambient light is captured before concluding the capture producing balanced image.

How about in SLR?  With flash you will need to change the shutter speed slow enough to allow the sensor to record ambient light.  Simple. 

However there is a problem with this technique.  When the subject is moving fast enough, this technique will result in trailing shadow like ghosts in front of the subject.  This is because the after flash fires, the camera's shutter is still open which means capturing the ambient light and subject movement that is recorded by the camera.

On this picture I move my hand from top to bottom, however the shadow makes the picture say as if my hand is moving from bottom top.


For shooting sports, e.g. running, this will make a picture that display the athlete is running backward which is awkward.

2nd Curtain Sync

2nd Curtain Sync is a feature of camera that order the flash fire after the exposure finished just a moment before the shutter closes.  This feature will eliminate the problem described above.

The image below shows that my hand is moving downward, and this picture shows it.  When photographing running athlete, having trails will give impression that the athlete is really running fast!  This image also shows quite detailed texture of my hand.


Another example of 2nd Curtain Sync. 

If I took this picture using 1st Curtain Sync, what I'll got is an orange shadow in front of his face.  With 2nd Curtain Sync, I can took what I'm intended, his expression.  His cute face is frozen on this picture while his trail which is unimportant is covered by his hair.

I recommend for freezing moments to set the flash to 2nd curtain sync.

Weakness?  Sometime we will loose moment because either flash fires too quickly or too late.  This is due to the need of prediction when to press shutter button, so the action happens when the flash fires.  Shooting in bulb mode might help in this case.

Having a flash mounted on the camera is handy on some difficult situation.

Don't forget: to check the white balance on the camera so the ambient lighting will match the flash lighting.  See my hand's picture that is a bit pale.

Photographing Ghost (in Indonesian: Penampakan)


Today's bonus is not a Sales Promotion Girl picture.  It was at 11.30 on my home's warehouse.  This room is rarely used and was about to be converted into family karaoke room.  When I was taking picture for the room architect, this is what I capture.

No, she is not a real ghost.  She is of course a real girl - alive and healthy - I'm not photographing a real ghost.  This is the technique on making transparent ghost like people with flash and 2nd curtain sync.  The basic is the same with freezing action, but you will need to make the subject transparent.

To create the trail:

  1. First the lightning should be weak enough, because overly strong light will made the trail will look solid and the background are overexposed.  However too weak lightning will render the object's walking trail invisible since the object is not bright enough to register its trail on the sensor.
  2. Set the desired exposure speed.  The exposure should be long enough to create walking trails.  On this example I put the exposure speed to 1.3 s, so the girl can walk for few metre to leave trail.
  3. Use of high ISO helps a lot.  This make the camera sensitive to light, so that even the slightest movement will leave trail.  I use ISO 1600 here.
  4. However too large aperture opening will not work, because you will need DOF.  I use f/16 here.  These values are not exact and can be changed to suit the needs.

When the flash fires, the subject will reflect the flash and register on the sensor.  However since the ambient light is enough to lit the background, the sensor which already records the background suddenly receives the image of subject.  Therefore creating transparent effect on the subject.