Condensation is an absolute killer to a photo shoot.  Once it sets in you can wipe and wipe and it will keep coming back.  So what causes condensation and how can you get rid of it and prevent it?

Causes of Condensation

protect21Condensation occurs anytime the lens is cooler than the ambient air temperature and there is enough humidity in the air.  Specifically the temperature of the lens must be cooler than the dew point.  It’s always a good idea to look at the dew point, when scouting and checking the weather.

You may be wondering how the temperature of the lens could get below the air temperature.  Well there are two common ways that this will happen.  The first is keeping your gear in an air-conditioned space and then bringing it out into a warmer environment.  That is the most common and usually occurs in summer months especially in the South. :)

Secondly there is radiation heat transfer or radiative cooling.  This occurs at night when the sky is dark and clear.  All bodies emit heat into the atmosphere.  It’s a fairly complex process scientifically but suffice it to say that the human body and your camera and lens will radiate heat off into the atmosphere.  When the dew point is close enough to the air temperature, condensation easily occurs. Wind will help to circulate the air and can keep temperatures better aligned and reduce any condensation effects.

Preventing or Eliminating Condensation

So now that we know some basic causes of condensation, how can we prevent it from occuring?

With air conditioned spaces the easiest way is to slowly transfer your gear from lower temperatures to higher ones.  I tend to put my gear in the garage or in the car well in advance of my shoot in order to make sure that it has enough time to equalize.  Some folks use coolers to ease the transition.  Others use ziplock bags. One thing you absolutely do not want to do is get condensation inside your gear (mold is nasty stuff). Most manufacturers are sealing their products much better now days, but you still want to be careful to ease the transition from cold to hot and hot to cold in order to eliminate internal condensation.

For clear nights there are a couple of easy ways to prevent condensation from occuring. Using a lens hood will help to reduce evaporative cooling. Having a fan circulate air onto your lens can be simple and an effective method to reduce cooling, but may not always be possible. Another way is to heat the lens, or insulate it.  There are several products that do this for you including expensive dew heaters or heat strips. They can be very effective. The Lens Muff is a great little product that can help but a simple handwarmer and a rubber band will do the trick.  The rubber band and handwarmer trick is my go-to solution. ;)

Check the conditions and when you expect dew to form be prepared to eliminate it before it becomes an issue. Once dew has set in there is no getting rid of it. :)

Follow Up

Do you have problems with condensation and dew? How do you keep condensation from occuring?