Monthly Archives: August 2015

Rogue Flash Gels – Universal Lighting Filters

When shooting Interiors, there is always the question of whether to use HDR photography with automatic post-processing or to make multiple shots with the assistance of a speedlight flash and process the resulting images manually.

While HDR is an easy way to achieve uniformly bright scenes, it is also this effect what makes some HDR pictures look unnatural. With a remote flash, an emphasis can be set very selectively in areas that should be highlighted or that suffer from low ambient light. The processing of these manual shots involves some extra time, but the results are often more appealing than those from automatic processing.

However, speedlights typically emit light of a cold temperature that is close to daylight (around 5,600K) as it contains a lot of blue wavelengths. For this reason, artificially added light often doesn’t match the color temperature of light available at the scene. In almost every residential house, the lighting is composed of several tungsten lights that emit some warmer color temperatures. Understandably, adding cold light to this scene would look inconsistent with the overall lighting.

As a solution for this problem, there are color correction filters – called color gels – that can be placed in front of the speedlight flash. Color gels are available in various colors to create all kinds of effects, but for interior photography, mainly one color is relevant – Orange. CTO – color temperature orange – flash gels are used to make the speedlight consistent with lamps of tungsten light. In other words – daylight from the flash combined with a CTO creates warmer light.

Color gels come in different densities. There are full, half and quarter CTOs that can be used depending on the color temperature available. While a full CTO converts the speedlight’s color temperature to full tungsten light (6,500K to 3,200K), a half CTO roughly converts it to something like a flourescent light color (6,500K to 3,800K) and so forth. Naturally, the stronger the color change is, the more blue wavelengths are filtered out, reducing the remaining light intensity accordingly. For instance, a full CTO blocks around half of the light (1 stop), and half a stop is blocked by a half CTO.

To improve my results for interior photography, I did some research to find a good set of flash gels. I found that the Rogue Flash Gels by ExpoImaging had a good number of CTO gels in their “Universal Lighting Filters” set and consistently received good ratings on Amazon and expert review websites. ExpoImaging was so generous and sent me a set of the Universal Lighting Filters for testing.

The Rogue Color Correction Kit includes a total of 18 gels in three sets of six gels.

  • 3x 1/2 CTB (3,200K to 4,300K) – f/stop loss = 1/2
  • 3x Full CTO (6,500K to 3,200K) – f/stop loss = 1
  • 3x 1/2 CTO (6,500K to 3,800K) – f/stop loss = 1/2
  • 3x 1/4 CTO (6,500K to 4,600K) – f/stop loss = 1/2
  • 3x Plus Green – f/stop loss = 1/2
  • 3x Full White Diffusion – f/stop loss = 1

The set also includes a cardboard disc with some useful instructions.

To balance your flash to the dominant ambient light source in your scene:

  • Use CTO gels to color balance flash to incandescent, tungsten, or halogen ambient light sources.

1. For 3,200K ambient light use Full CTO
2. For 3,800K ambient light use 1/2 CTO
3. For 4,600K ambient light use 1/4 CTO

  • Use Plus Green gels in combination with CTO gels to color balance flash to fluorescent ambient light sources.

1. For 3,600K fluorescent tubes use Plus Green + 1/2 CTO
2. For 4,300K fluorescent tubes use Plus Green + 1/4 CTO
3. For 5,700K fluorescent tubes use Plus Green

  • Use CTB gels to color balance flash to shade, or blue sky ambient light sources.

Finally, every gel is placed next to a thin white separator sheet that helps finding the right color. I found it nice that all filters, the separator sheets and the cardboard disc had already been packed into the small fabric purse, and therefore doesn’t require any preparation. Also, it is particularly useful that the relevant characteristics of each gel (type, f/stop loss) are printed on a side flap of each gel.

The gels are applied to the speedlight flash by one of the rubber rings provided with the kit. The rings fit tightly on the flash and hold the gels firmly in place. I like the concept how the gels are applied to the flash because they cover all of the flash aperture so that no uncorrected light can leak out. A further, notable advantage is that each set of color correction gels are provided in triplicate, so it won’t matter too much in case that one gets damaged or lost. Thumbs up!