Rosco CalColor - One Flash Colour Effects

One off-camera flash to create a coloured background with Rosco CalColor

Following from my blog about creating an enhanced sky using Rosco ToughPlus Green gel and Strobist's blog "Rosco CalColor: Whatever You Want It To Be" I have created images using CalColor gels to change the background colour in outdoor and studio based images.

If you only have one off-camera flash or Speedlite and need or desire to change the background colour in a photograph, this is not as difficult as it may seem. You will need to get your head around some basic colour theory; anyone who has worked with colour correction filters or has experience of colour printing will understand the principle withe ease.

When you put a Rosco CalColor gel over you flash, it will create a local colour cast equal to the gel on the flash. When you correct this colour cast either in post-production or by using an in-camera custom white balance, the local colour cast is corrected by introducing the complimentary colour to the colour cast. The local colour cast will be corrected, whilst the rest of the scene will take on the complimentary colour. If you refer to page 22 of Rosco Filter Facts there is more information on the CalColor filter set and a colour wheel - on the colour colour wheel opposite colours are complimentary to one another.

For this exercise I didn't worry about an in-camera custom WB. I made sure I shot a white card with a flesh tone reference before the shoot and made my corrections during post-production. Using an in-camera custom WB will allow you a rough preview of how the finished images will look.

The first frame shows the scene as the camera recorded it - a grotty industrial area.

Left frame: ISO 400, f5.6, 1/125th.
Right frame: ISO 200, f5.6, 1/160th.

The second frame I've under exposed the ambient light to create mood. I wanted to warm up the background which considering the large area was impractical with lighting so opted for #4215 and #4230 to create 45 Blue CalColor gel on my flash.

Left: Uncorrected frame with 45 Blue CalColor.
Right: Corrected on Adobe Camera Raw (ACR).

As you can see, the WB frame shows a distinct blue colour cast, which when corrected introduces yellow into the background warming it up.

Before WB correction in post-production.

This frame of Ollie is a bit too cool until the colour correction is applied. As you can see, the foreground is reasonably neutral, I do prefer warmer flesh tones and the background much warmer than the unfiltered version.

Corrected in post-production.

Choice of background here was critical; by using a Canon 100 - 400 mm f4.5/5.6 L Series IS zoom lens I was able to isolate Ollie against selected parts of the background. In this frame the background is the side of the building top right of the wide shot giving a pale tone to show the warming effect of the #4215 and #4230 to create 45 Blue CalColor gel once corrected.

In view of the distance I was working from Ollie, about 20 yards, Ben Potter acted as my Voice Activated Light stand. Ben is a talented photographer, Photoshop genius and excellent assistant - possessing more than the requisite 2 brain cells and a very well developed sense of humour.

The light was a Canon 580 EX II Speedlite with a radio trigger fired into an ancient Lastolite 2 feet square brolly soft box with the white diffuser panel removed. I particularly like this reflector as it acts like a parabolic brolly giving direction to the light but with soft gradation to the shadows.

One light in the studio.

In the studio we applied the same principle but used a plain white background cyc paper roll which was 4 feet behind Ollie. Again, one light, no reflectors or fill light.

Again, as shot and corrected in post-production.

Admittedly, there is a fair amount of ceiling and wall bounce as Paul's studio is what I refer to as a subtractive studio - you need to use black flats to control the light; whereas an additive studio is painted black and you add the light and reflectors where you want.

As seen on the camera preview screen without in-camera custom WB correction.

As you can see, this frame is as it was previewed on the camera screen. You may want to faff around setting a custom WB in-camera in order to get a rough preview of the images you shoot.

After corrections applied in post-production.

Once the corrections have been applied in post-production we have a relatively neutral foreground subject with a green background. In this example the flash was gelled with CalColor #4760 60 Magenta.

Do remember with this technique any light that illuminates the subject (fill, hair, kicker) should be gelled the same way as the key light otherwise they will take on the colour of the background!

The Rosco CalColor kit retails for around $50 or £40 and is widely available from pro photo dealers. For more information click here.

The 10" x 12" sheets can be trimmed down to create at least three clips of each colour for Speedlite use leaving a good size piece for use with your studio lights. Make sure when you trim the gels that you have a means of identifying each piece. I use white postal labels fixed to one of the narrow edges of each gel and store then in a clear CD sleeve.


  1. I was wondering where I could purchase the color gels? Do they have a site and will the gels work for a pop-up flash?

  2. Hi, you can buy the CalColor kit from most good pro photo resellers - this link will take you to the page for your home country

    The filters may be used with your pop-up flash and will need trimming to a smaller size in order to do so.

    Good luck!


  3. Really i appreciate the effort you made to share the knowledge.The topic here i found was really effective


Post a Comment

Popular Posts