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Calibrating the JVC HD250 - The TrueColor Configuration
About a year ago, beginning of 2006, I published the first article about calibrating the JVC HD100. I didn't expect it would cause a big reaction among the community of shooters but the configuration reported in the article, dubbed TrueColor, suddenly became one of the most widely used configurations for the HD100. Emails started arriving from all corners of the world telling me how TrueColor was used in commercials, documentaries and indipendent features and how it helped people finally achieve the colors that they expected from their camera. I can't tell how satisfying that is. More important it confirmed that the HD100 was capable of creating some great images. The puzzling thing is, why JVC doesn't provide the camera with better factory settings. Neverthless TrueColor helped achieving the potential of the camera.

TrueColor was born out of frustration and necessity. Frustration that my HD100 was not delivering the colors that I expected, and necessity to make it better. After all, I thought, this is HD, not some pesky 4:1:1 color coding, the colors must be there, somewhere. Fortunately JVC was kind enough to provide extensive adjustments for a sub $6,000 camera and so the only thing that remained to do was to find a way of adjusting the camera to its best. Keep in mind that when I started I didn't know if the process would improve the colors. My basic assumption was that the camera should be able to reproduce colors that are close to reality and when I was reviewing my footage I saw colors that were "dimmer", less vibrant then the ones that I saw by naked eye. Any step closer to a 1:1 reproduction should bring improvement.

The core concept of calibration is objectivity. You cannot calibrate anything by using your eye. You need reference points, you need objective tools. There are three tools that you use for this operation: a DSC color chart, a Waveform Monitor and a Vectorscope. The reason for the chart, as compared to, say, some flowers or other nature-inspire multicolor objects, is simple. The DSC charts are spectrometer-verified to reproduce colors in the range of the colorimetry supported by the camera. Specifically, DSC creates its charts to place key color components in the right location in the Vectorscope. When this fact is guarateed, if the colors don't fall in the right place, you keep changing the colors matrix until they get to the right location. At that point your color mnatrix is calibrated. DSC verifies every single chart to be accurate and that is your objective starting point. DSC Labs has been around since the early 60's and they followed all the developments of color coding in the television and SD/HD world. DSC makes charts for all kind of budget and I think that investing in one of their charts is probably one of the best career moves that you can make if you want to become a professional. can tell you one thing: learn to use one of their charts and your images will improve dramBesides serving for color calibration you can use a small FrontBox HD chart at the beginning of each clip that you shoot as a reference chart and make the life of the color corrector specialist easier and achieve more consistent colors in your production. I tape a Frontbox chart to the slate so that every time we slate a shot I get my colors and grayscale values at the beginning of each clip.

After the sucess of TrueColor a lot of people started emailing me about doing the same for the new series of JVC cameras: the HD200 and HD250. These new cameras, while retaining most of the characteristics of the HD100, use a different color matrix and the configuration files designed for the HD100 don't work. Voice of this reached JVC and together with Marion Ciliberto, manager or the West Coast Branch, we agreed that it was time to port TrueColor to the new series of cameras. This is an example of cooperation in this industry. JVC provided an HD250 for 3 weeks for me to use. DSC labs, specifically its founder David Corley, heard of this and they immediately sent me a 24" ChromaDuMonde chart plus their brand new backfocus chart "Fiddleheads". I will cover the usage of Fiddleheads in a separate video that I'm preparing. Armed with all the necessary tools it was now just a matter of spending the time to calibrate the camera.

The process is pretty straightforward. First thing that I do I load one of the stock configuration settings that more closely resembles my target. In this case I decided to try the "CinemaHD24p". I then disable most of the "enhencements" like detail, knee, black stretch. I try to get to a standard, linear setup from where I can judge the colors and latitude without corrections from the camera many features. Those functions can be added later but for now they only prevent an objective avluation of the signal.

The next step is to zoom in to the grayscale section of the chart and adjust the range by using the WFM. Open the iris until the white chips register at 100% then look at the rest of the "steps" in the chart and check the black level. Usually the black chips doesn't touch the 0% level. This is usually because digital cameras, especially the prosumer ones, are considered "video" cameras and the destination is generally TV. For North America this means that blacks should be at 7.5 IRE. I like trating digital cameras as they were intended for film application and leave the color correction in post. I want to be able to capture as much detail in the blacks as possible. By adjusting the master black and bringing the black level at 0% we can verify that each step in the chart is registered at the right level in the WFM. This means that blacks will be defined even when they will not be initially visible on a monitor. The verification is simple. Shoot some footage, bring it inside Final Cut Pro, add a Color Corrector 3 Way and raise the blacks a little. If you start seeing detail in there then you know that the camera recorded image information. If the blacks go up but no detail is revealed then you have crushed blacks.

Now let's take a look at the different results with the Waveform monitor:
This is the output from lighting the ChromaDuMonde chart evenly and setting the aperture and Master Black properly. We see an even distribution of each of the 11 steps of grayscale patterns in the chart. The middle element denotes where the gamma setting is. This was taken wih an aperture of between f5.6 and f8.
Next, I left everything untouched, same lights, same aperture, and I loaded the stock configuration "CinemaHD24p". As you can see from the result this configuration is "slower", the white chips register in the high 80s instead than being at 100. This first observation tells us that this configuration will require more light. In other words, the same exact scene will need to be lit differently in order to use the stock settings. Not good. Not good because, besides the light problem, this configuration will likely create more noise. With 4:2:0 color encoding dark areas then to blend together losing detail and that in turns generates a lot of "dancing pixels". Also the black level is at 7.5 instead of beeing at 0. We lost light and we have lost latitude with this configuration. Just to be totally accurate I checked the knee settings for this configuration, because the knee could be the cause of the lowering of the highlights. It turns out that the configuration uses automatic knee. I checked it to manual at 100% and the result was the same.

Let's see now exactly how much light we need to achieve the same levels for the highlights.
This is exactly the same setup but at f4.0, so we basically need one f-stop more to get the same level of light inside the camera and we still don't achieve the same latitude of TrueColor. In fact we see that the black chip is actually a little higher than in the previous example. So I think that it's safe to say that TrueColor gives you about 1.3, 1.5 f-stop more of latitude compare to the out-of-the-box experience. In my book this fact alone pays for the cost of the chart. And remember your DSC chart will work for many, many cameras.
I forgot to mention another thing, I use the grayscale area of the DSC chart for white balance. Since the chart is guaranteed to be neutral this is a really good way of setting white balance in your camera. At this point we have exposure, gamma and black set right, let's move on to the next step: setting the color matrix.