Second Curtain Sync and the fire dancer

Thirty second exposure on slide film using flash and second curtain sync.

Second curtain sync, also called rear curtain sync, is a flash-related feature found on many SLR, DSLR, and mirrorless cameras.  It allows the user to fire a connected flash unit at the end of the exposure, rather than at the beginning, as is the norm.  It is useful in certain situations as it produces a more natural-looking exposure when timing is an issue.

So, what's with this 1st-curtain/2nd-curtain stuff anyway?  This doesn't apply to global shutters, leaf shutters, or electronic shutters, but only the good, old-fashioned focal-plane shutters so many of us are familiar with.  I've created a diagram for the process of how 1st and 2nd shutters work that is posted below.

Movement of 1st and 2nd curtain shutters for focal-plane shutter cameras.

There are two shutters in cameras equipped with focal-plane shutters.  The first one, called the first-curtain shutter, blocks light from reaching the sensor.  When the exposure takes place (shutter button pressed), this shutter moves out of the way to expose the sensor to light.  As soon as it gets out of the way, the flash fires if it is turned on and if it is set to first-curtain sync, which is the default setting.

The exposure is free to take place now for the established time.  This can be anywhere from 1/200th of a second to 30 seconds or longer, depending on the camera's shutter speed.  if a longer exposure is desired, the manual exposure mode will have to be used and the time setting set to BULB.  There are various ways to use this feature, which I will not go into in this blog.

At the very end of the exposure, before the second shutter starts to move, the flash will fire if it is turned on and the camera is set to second-curtain sync.  The moment it fires, the 2nd curtain begins to move, and the exposure is finished.  Both shutters reset in order to get ready for the next exposure.

I have only used 2nd curtain sync a handful of times as the default setting is sufficient for most shots.  But there are times when you want the flash going off at the end of the exposure, not the beginning.  This usually involves long exposures and situations where you want the flash firing at the end, not the beginning.  

Thanks for reading.

Eric Svendsen     www.ericspix.com

Comments

Post a Comment

Popular posts from this blog

Harjit Bahia - Science teacher and colleague from Garibaldi died August 2, 2024

Image
You will be missed Mr. Bahia.  You made a difference and we are sad you are gone. I keep in loose contact with my fellow retired teachers from Garibaldi Secondary School.  I talked with my long-time friend, Mike Lynch, today, and discovered that Hargit died over the summer.  Unbeknownst to him, he had an underlying heart condition and passed away after working out on his treadmill.  The date was August 2, 2024. I was shocked to hear this.  He was only 49 years old, turning 50 some 3 months later.  It was a shock to everyone, for he was loved by all who knew him.  As a teacher, Mr. Bahia was kind and fun.  He contributed to students in many ways and was always available to help those in need.   For myself, I knew him as a fellow science teacher and taught in the adjoining room to him.  He was always available to help, share ideas, and work together.  Easy to approach, I found that I could talk to him about anything and appreciat...
Read more

My longsuffering search for the Western Meadowlark

Image
Am I going to disturb a species I am photographing enough to negatively affect its relationship with the ecosystem?  This is an important ethical question that needs to be asked when looking to photograph a particular species.  And it's one that I don't think we do nearly often enough. I recognize the desire to capture remarkable images; I have been in search of premium photos the bulk of my adult life.  There is the personal connection - just the joy associated with doing something well and the praise we seek when others recognize it.  There is the professional connection - doing something as part of a job, assignment, or class.  Then there is the financial connection - the hope to win a contest, publish an image, or sell prints.   These are all worthy goals in their own right, but none of them should be the reason behind disturbing a species, especially ones that are endangered or are at a critical period in their life cycle.  Essentially it boi...
Read more

Munson pond - before and after road development

Image
Left - Google maps view of Munson Pond as of May 15, 2025 Right - Future view of Munson Pond from Google maps Munson Pond is a jewel of Kelowna.  Even though it used to be an open gravel pit, it is now home to countless birds and mammals and a haven for humans needing peace, a breath of fresh air, and a touch of nature.  Western Pond turtles are protected under the Endangered Species Act.  Their population is such that people lose count when trying to ascertain their number.   With the proposed road development, Munson Pond will lose valuable ecologically important land, will suffer from an increase in urban traffic, and will likely be affected by nearby housing developments that are sure to come.  All of this development will put more pressure on the inhabitants and result in a decrease in both biodiversity and population.   A further injury to the pond will be an increase in eutrophication due to nearby residential and commercial development....
Read more