At AbelCine, we produce many scene files for a variety of cameras, each designed to improve both look and performance. We post these files on our website for anyone to try out, which has resulted in a lot of great feedback and many different questions. The most common question we receive is about matching the look of two different camera models. We talk a lot about working with Raw and Log cameras, but much video production today doesn’t go through extensive post color correction, so matching two different cameras before shooting has some big advantages. Recently, I was asked how to match a Sony F3 to a Sony FS700U, which is a fairly common request. We do this type of matching as a service at AbelCine, but for the benefit of you, the reader, I wrote up this outline of our process.
PICK A HERO
To get started, we need to decide which camera we’re matching from and which we’re matching to. Some cameras are more adjustable than others, with picture adjustment options that include things like gamma modes, matrix adjustments and other color-correction tools, while other cameras have only limited control over things like saturation and hue. Our least adjustable camera should become the master or "hero" camera, and the adjustable one becomes the "match" camera. In the case of the F3 versus the FS700U, the FS700U would serve as the master, and I then would adjust the F3 to look like it. Some people may take issue with this, but to achieve the best results, our least adjustable camera should be our starting point. The good news in this situation is that the FS700U had the look that the client was going for, so I could comfortably move forward.
EXPOSURE & BALANCE
Having decided on our hero camera, I now could start the process of matching. The basic setup for this is pointing both cameras at a DSC Labs chart with both grayscale and color on it. I love their Chroma DuMonde charts for this. I use a soft light source to light the chart, and I make sure to use a skin tone reference (humans work best).
The next step is to set matching exposures on both cameras. This can be trickier than it sounds, so I’ll explain. Start off by setting the hero camera lens to around an F5.6, which is approximately the middle of the aperture range. If your lens aperture is open wider than this, lens flare may affect the image. Next, set the hero camera to its base ISO or 0 dB setting. In my example, I’ll set both the F3 and FS700U to 0 dB. It’s important not to go below the base ISO (or into negative gain), as it may have an effect on the dynamic range of the camera. This is an important fact to remember when shooting with digital cameras, in general. Now, view your hero camera’s picture on a waveform monitor of some kind. Check to see where the middle area of the chart falls on the scope. It should land around 50% to 60% on the scope; if not, adjust the lighting as needed.
Next, compare the exposure of the other camera; most likely the two won’t match. Remember, our master camera is the least adjustable, so we’ll leave that be and start changing things on the match camera. Adjust ISO, add NDs and adjust aperture as needed to match exposure.
Once exposure is aligned and around 50% to 60% on the waveform, the next step is to run a white balance. A white balance will even out the red, green and blue channels of your video. Use the DSC Labs chart or a white card to set white balance on both cameras. This is perhaps the most important step of this whole process; if white balance isn’t even between your cameras, they will never match.
Now that we have white balance and exposure basically lined up between the two cameras, it’s time to start matching the overall contrast of the image, something we refer to as the "gamma curve" of the image. Using a grayscale chart, like that found on the Chroma DuMonde, allows us to visualize a gamma curve on a waveform. We can use this to help match the contrast of our two cameras. These adjustments are key to matching cameras because contrast has a huge effect on the appearance of color. Our match camera hopefully has a couple of different gamma modes to choose from, as well as options like black level, knee and slope adjustments.