Off camera flash – Eric Budworth

Hot Shoe - PC ConnectionOff camera flash is a phrase which is often used in photographic circles and to newer recruits to this pastime may not fully grasp the technicalities of what it entails. The phrase “off camera flash” is very clear to most adults as meaning a flash unit not attached to a camera!! ………”easy peesy”  ……. not quite the case in reality

Flash cable connectors

Over the last number of years camera manufacturers have decided not to fit a “Sync. Socket” to a large number of their cameras except the higher end “pro. spec.” models, which are out of reach of most amateurs. Some camera makers do however offer an alternative method to fire a flash off camera, using dedicated cables which fit into the hot shoe and this cable has a duplicate flash shoe at the other end which holds the flash. This type of cable duplicates all of the controls & modes which are available to the on camera flash unit, this makes then extremely versatile. These are available often at grossly inflated prices.

The other work-around is to purchase a “Hot-Shoe to PC” adaptor. This device has a sync socket fitted as well as a hot shoe connection. A cable is connected to this socket and the other end connects to the flash unit which is held off camera. Another alternative to this is was is known as a “slave unit”, this small device has an light sensitive electronic circuit which trigger a flash unit when it receives a flash of light, this flash of light could be from another flash unit…..i.e. the small inbuilt flash which is built into an existing camera.

In the accompanying pictures you can see some types of hot shoe adaptors and slave units as well as cables required to connect to them.

Flash Unit Adaptors

In order to try this method of flash illumination you will require the following:-

  1. A Hot Shoe to PC adaptor.
  2. A PC cable……..length what ever is available, the longer the cable the further the flash from the camera.
  3. A suitable flash unit.

The above is suitable for use with an SLR type camera Digital or Film.

For use with compact cameras you’ll require a slave unit as most, but not all compacts don’t have a hot shoe fitting. You’ll need the following:-

  1. A slave unit…….(these are available from good photographic stores & maybe camera markets)
  2. A suitable PC cable to connect the flash to the slave unit. There is no physical connection to the camera.

In this scenario one would use the onboard camera flash to trigger the accessory flash connected to the slave. Depending on the subject to be photographed some sort of shielding may be required to prevent the on board camera flash effecting the final result of the image’s illumination. A piece of white card is often used in these cases thus preventing the direct light from the camera’s flash reaching the subject but still leaving the “overspill” to trigger the slave unit.

Off Camera Flash set up

I’ve attached some images showing the set up I used to take some of the shots. The portraits are copied from camera books and are included to show effects of flash position relative to the subject matter.

Off Camera Flash.1

I do not claim credit for these.

Most modern flash units made by the camera makers are suitable for these types of photography when used on the makers camera …….Canon on Canon, Nikon on Nikon, etc.,


We are dealing with Direct Current in this instance !!!

Do not use any older style of flash or one which you may have had since “Pontius was a Pilate” as some of the older flash units used very high flash trigger voltages which could fry your modern camera’s internals if connected directly to your camera whether it’s an SLR or Compact.

Modern cameras have quite low trigger voltages mostly below 20 volts many as low as 6 volts.

Some old flash guns have trigger voltages in the realms of 240 volts I’ve actually come across some where the voltage is as high as 330 volts !!  These high voltages actually melt the camera’s internal trigger switch which is usually activated by the shutter operation.

Before using any of these older flash units find out what your camera’s flash trigger voltage is ; this can be usually found on the web under specifications relating to your particular camera or from the manufacturer.

Next find out the trigger voltage of the flash you intend to use, this needs to be the same or lower than the camera’s flash trigger voltage.

Off Camera Flash


To get the correct exposure one must first set your camera’s shutter speed to suit the flash.

As all cameras have a maximum shutter speed at which the film or sensor will successfully record all of the image illuminated by the flash this speed must NOT be exceeded otherwise portions of the image will be blacked out with a camera fitted with a Focal Plane Shutter, this means Digital and Film SLRs as well as some of the newer types of camera which no longer have a reflex mirror fitted. These cameras are the compact type with interchangeable lenses.

In order for the exposure to be right the shutter speed and aperture combination must be set to suit the ISO setting on the camera. This used to be measured with a flash meter (a fairly expensive accessory) but with the advent of digital cameras this item is not really needed.

Set the flash unit ISO to the same as the camera setting and switch the flash to manual setting if available, set the camera shutter speed to the fastest flash sync. setting for your model camera, mostly 125th of sec.  Next set the camera’s aperture to around f5.6., set the camera to manual focus and focus on your subject then fire off a test shot, after which check the exposure on the camera’s LCD display. If the image is too bright (over exposed) reset the aperture to f8; if too dull (under exposed) reset aperture to f4. Repeat this until you are satisfied with the result.

I realise that this is a trial and error solution but without going into a lot of calculations regarding aperture/distance and whether the flash is set to Auto or Manual or if the flash has a variable adjustable output I feel this is the easiest way to get the best exposure.

Some people will say that one can move the flash unit closer/further from the subject and this will alter the exposure…..quite true ! however if you are holding the flash in one hand it’s not that simple as if you move further away the focus will alter. There are other ways of achieving exposure adjustments but I won’t go into that. Suffice to say the “Shoot & Review” method is probably the simplest and most novices will soon get the hang of it.

Off Camera Flash.2

Hope this will suffice James…it’s a bit long but you can edit it if you feel inclined.