If you’re new to video cameras or even mirrorless cameras with video settings some of the terms might seem daunting.
In this article I’ll explain each important setting as simply as I can.
Watch it now:
Just to clarify, I’m referring to the adjustments and settings you can manipulate for exposure and color. I’m assuming you know the basics like shutter speed, aperture, white balance and ISO.
The opening of your lens, it determines how much light is going in. For video and cinema, people use T-stops instead of f-stops. T-stops give a more accurate representation of the actual light hitting the sensor, so for example, if you have a whole series of lenses for the same brand, a T4 across all lenses will give the same exposure.
With f-stops, an f/1.4 at one focal length might be slightly darker or lighter than and f/1.4 at another focal length, even from the same manufacturer, and sometimes even copies of the exact same lens.
To know more:
The Shutter Angle
The shutter angle is just the shutter speed expressed as an angle instead of seconds. You could use a simple formula to convert, just the link in the description if you like to do the math.
But otherwise, as a beginner, all you have to know is the angle goes from 0 to 360 degrees, and 180-degrees is where you want to be at most of the time when you’re starting out.
If you’ve ever shot on film, you’ll know that film comes in fixed ASA ratings (ISO). But how can a modern camera sensor move across an incredible range, like say, ISO 100 to 100,000 or so?
The answer is that what you think is ISO is in fact, gain. Gain is electronic manipulation of the sensor image (this is a simplistic explanation of a really complex subject). This is why every sensor has a ‘native ISO’ – the ISO at which it delivers the maximum dynamic range.
This native ISO is 0 gain, or more specifically, 0 dB gain. Gain is measured in decibels because it equates well with the inverse square law of light. On video cameras, you’ll see a gain setting that works similar to raising the ISO on a DSLR. The end result is the same, though there are some ‘hidden’ differences and similarities between ISO and gain:
- ISO is fixed to represent photography standards and light meters. E.g., ISO 50, 100 is a universal thing. Gain is camera-specific and science-specific. E.g., 0 dB for Camera A is not necessarily the same as 0dB for Camera B. Before the DSLR revolution ISO was only used in film. Videographers always dealt with gain.
- Manipulations for both gain and ISO are done on sensor RAW data, for maximum image quality. This is why it’s better to use the in-camera gain or ISO rather than boost levels in post processing. Cameras that shoot RAW do so at the native ISO (0 dB gain) so you can adjust this in post production.
- Both produce noise, and this is dealt with internally. Moving away from 0 dB and native ISO is always a recipe for adding more noise.
If going up from ISO 50 to ISO 100 doubles the light, how much will be ‘gain’ equivalent? 6 dB. Every 6 dB doubles the light. It also adds 6 dB to the noise. This makes gain a better variable for understanding noise. Two stops would be 12 dB and so on.
What should you do if faced with gain or ISO or both? Find the native ISO and equate that to 0 dB. Then move 6 dB for every ISO stop and you’re good to go. If the gain levels in your camera is not in 6 dB multiples, then use the in-camera meter or light meter to see how many stops each gain setting will provide, and commit that to memory. That’s easier than pulling out the scientific calculator.
That’s all you need to understand or care about gain.
White balance is one of those crucial video settings that a lot of people forget in the heat of the moment. When in doubt, the least you can do is set the camera to auto white balance.
What is white balance? In layman’s terms, white should appear white, and not blue or orange or any other color.
One additional feature you’ll find in video cameras is a green-magenta setting. Sometimes if you’re using cheap LEDs, HMIs or flourescent lights, you might get a green tinge to your image, and this setting allows you to correct for that.
Make sure you have your white balance right before you roll.
To know more:
I have already explained gamma in What is Display Gamma and Gamma Correction?
Let’s say you have a suitcase and want to pack for a holiday. Will you lay your clothes out straight, or will you fold them to save space? Folding clothes is the equivalent of applying a gamma. You’re trying to fit one thing into another to save space (or something).
In the article about latitude and dynamic range, I explained how scenes can contain dynamic range that is greater, equal to or lesser than the camera dynamic range. When you have the latter, you have latitude. When you have the former, you need to find some way to make it fit. There are only three methods to make it fit:
- HDR – recording separate images and merging them later
- Gamma – folding your wide DR scene to a small camera DR bag
Let’s take this scenario: You have to put clothes on a clothesline, but with the condition that they must be equally spaced apart. If the clothesline is straight, you can fit x number of clothes on it. However, if the clothesline is curved, you can fit more than x clothes on it.
Look at this image:
The image is for representation purposes only. M stands for middle gray.
If a scene has 16 stops of dynamic range, and the representation of this is ‘linear’ (actually it’s not correctly linear, but Rec. 709, which contains a gamma in itself) you can fit 9 stops of the scene on the sensor. This is assuming our sensor can only hold 9 stops of DR.
Now, by some creative math, we stretch the clothesline (gamma) a bit more. Make it curvier than Rec. 709. Suddenly you can squeeze in 2 more stops. But there’s a catch. If you watch the latter image, it will look ‘flat’ and ‘lifeless’, as if the whole scene were shot through fog and desaturated for good measure.
Now, the gamma curve can take many forms:
The above are not the real gammas, just representations to show you how the flatter gammas try to increase the length of the clothesline by becoming more curvier.
The last one’s a joke. Or maybe not.
IRE is the normalized luma representation of voltage and light in terms shooters can understand. Easier to understand 0-100 IRE than 0.285 mV. For HDTV Rec. 709, 0 is black, 100 is white and 100-109 is ‘super-white’ or headroom. Just because you have this entire range doesn’t mean you can use it all. That’s what the next section looks at.
From the IRE values, you can find out how many stops of DR Rec. 709 can carry. It happens to be 26.77 = 109. This means, Rec. 709 is not capable of more than 6.77 stops at its best.
To know more:
The Response Curve
Whenever you buy ‘gamma’, you get a free graph like this:
There are other names for this graph, but I’m going to use the generic term ‘response curve’. Light hits the sensor, then it’s all a blur, and you finally get an image. In between you have a few knobs to turn around. The response curve basically says: If you change the light in so-and-so fashion using the knobs at your disposal, I’m going to do this to your image. We already saw that gamma is one of the major goons in this jungle. Now let’s meet the little puppies.
The chart includes several important ‘regions’ and ‘points of interest’. Understanding these is not hard, but it takes practice to learn how each specific camera is designed to handle light and color and then apply the knowledge for practical use.
The two regions we are concerned about are:
- Toe or pedestal – the black/shadow side
- Shoulder or Knee – the white/highlight side
Pedestal, Black level or Master Black
The video signal cannot go below 0 IRE (which is pure black). The pedestal (or base) refers to the setting that changes how the black portion (toe-end) behaves. If you ‘raise the pedestal’ (positive number), the shadows lift. If you lower the pedestal (negative number), you will crush the blacks.
The proprietary algorithm of each video camera tries to respect your wishes without touching the mid tones and highlights, though the degree to which these are affected is totally dependent on high up or down you push it.
Newbies often mistake the flat-looking image you get by raising the black level to mean an increase in dynamic range. This is not correct. Once the gamma and color space are set, the dynamic range is pretty much etched in stone. The black level is akin to crushing the blacks or raising the shadows in a color grading application.
If you want to picture it, imagine moving the black dot up the vertical axis (raising the shadows) or down the vertical axis (negative zone, crushing the blacks). Nothing else moves.
Instead of raising or lowering the black levels, one could also adjust the curve only for the toe-region (Gamma over a gamma). It tends to look like this:
This keeps the absolute black level constant, but changes how it ‘rolls-off’.
Knee is opposite to pedestal. It is used to get the highlight response you want.
The setting for knee is either:
- On – you want it
- Off – you don’t want it
- Auto – let the camera decide based on a preset
Typically, cameras offer more options for knee than pedestal. I’m not sure of the exact reason, but my guess is that the dynamic range of a camera is limited, and the most important element in a shot is the skin tone. Once a camera operator exposes ‘correctly’ for skin tones, then the blacks and whites are allowed to fall where they may.
Our eyes are used to objects crushing to black when the dynamic range of a scene goes too high, but we don’t see blown out highlights naturally. This could be why, along with the fact that digital sensors have poor highlight roll-offs, that the knee setting is given more control options.
The first important setting for knee is the knee point. It is the point beyond which the highlights are affected. Sometimes cameras have their own scale while on others it’s the IRE rating or a percentage.
This is the ‘white gamma’ (Slope is gamma) that allows you to control how the highlights roll off. You could make it ‘drastic’ or ‘smooth’ but obviously there is no one correct setting, and this must be adjusted by eye (or waveform monitor) on location for every shot.
The problem with knee in general is that you need either of these two conditions to exist before it can be useful:
- The camera has good highlight dynamic range.
- You expose for the shadows (underexpose) to keep more highlight detail for knee to work.
Either way, without something to play with, the knee setting will hardly matter. Like the black level, it does not increase dynamic range by itself, but only gives us the impression of doing so.
White level or Clip level or White clip
This is an absolute setting that tells the cameras – nothing beyond this point! Anything that crosses this threshold is clipped. I have found this setting to be useless for artistic work, though its most important use is for ensuring highlights stay within the Rec. 709 or TV broadcast specifications (100 IRE for full swing, 92% for studio swing).
Instead of the white level or clip, I prefer the next setting.
Zebra (1, 2)
Zebra is just an indicator (looks like zebra stripes) on the camera monitor/LCD screen/viewfinder that highlights which regions are above a certain threshold (in IRE). E.g., if you set the Zebra at 90% or 90 IRE, any regions in your scene that go beyond this point are highlighted with ugly-looking but absolutely useful zebra stripes. They are not recorded in-camera (you won’t believe that there are professionals who think it does!!) nor are they passed on via HDMI or SDI.
The main zebra (always displayed in stripes), is Zebra 1. Some cameras allow you a second Zebra for additional display (spots instead of stripes). Why on earth would anyone want a second zebra when the first one is annoying as it is? Sometimes, ‘professionals’ like to expose via waveform/IRE rather than by eye. One tradition is to set the Zebra 1 at 70 IRE, because that is where the ‘limits’ of Caucasian skin tones lie, and use Zebra 2 for 90 IRE or 95 IRE to keep highlights from blowing out.
I was dumb enough to follow this advice before knowing that the IRE level of 70 was intended for Caucasian skin, while my skin is Indian (it’s a new color, I’m going to patent it). What do you do in a scene with non-Caucasian skin-types?
But there’s also a problem with holding on to 70 IRE for Caucasian skin. There’s a large range of tones that fall under the ‘Caucasian’ paradigm. It changes on whether you’re in the sun or shade. It changes if you’re dead or blushing or tanned or have makeup on. It changes if you turn into the hulk.
For these reasons and more, I have long abandoned placing skin tones at IRE levels, and recommend you use your eyes instead. Also, since skin tones are no longer an ‘IRE’ problem, I restrict myself to Zebra 1 to check for blown out highlights and that’s it. If you’re not delivering to broadcast legal limits at all, then you really don’t even need the Zebra.
In a war between zebra and the histogram, whom should I believe? In other words, if the zebra clips but the histogram doesn’t, what should I do? Here are some differences:
- Zebra is calibrated to IRE, which is normalized luma (Y’ in Y’CbCr) and only looks at the luma information as a whole.
- Histogram is calibrated to RGB. If your camera does not offer separate RGB histograms, it is impossible to tell (without scientific testing) whether the histogram clips because of one channel or both or all.
Remember, the zebra is calibrated to Rec. 709 specifications, while the histogram is calibrated to the sensor RAW feed (sometimes, as in the case with Red cameras).
So much for the exposure settings. Let’s add a little bit of color.
Hue and Saturation
Hue changes the overall hue of the scene (like adding a tint or wearing colored glasses). Saturation raises or lowers the saturation of individual colors. Sometimes, you have saturation controls for the toe and shoulder regions of the response curve individually.
Sometimes, you can change the saturation using picture profiles or presets as well, and the use of it is entirely subjective.
As far as hue is concerned, it’s a rare setting, because you can change the hue better and more accurately with white balance and the color matrix.
Color matrix and LUTs
The color matrix is an overall LUT-like matrix (LUTs are matrices as well, I’m just playing with words here) that transforms the colors on your image. Presets, picture profiles, scene files, creative styles, etc. are all matrices that affect the colors in an image in a ‘specified pre-determined’ way. It’s baked-in, more or less.
On professional and prosumer video cameras, you can get finer control with the color matrix setting, which typically offers these adjustments: R-G, R-B, G-R, G-B, B-R, B-G. What should you note? The fact that these are not R, G and B separately, but in pairs. This means, by changing one channel, you also change another channel. How do they relate? Here’s a cool rule of thumb I learnt from Andy Shipsides of Abelcine:
When adjusting any one of these combinations, the first color (R, G or B) will be affected in saturation and the second color (R, G or B) will be affected in both hue and saturation.
Color depth (sometimes ‘matrix’ or another name)
Sometimes you can change individual color channels as well. Usually they are:
- CMY (Cyan, Magenta, Yellow)
The combination of hue and saturation is called phase. In the rule of thumb, we have seen that the first color will change saturation while the second will change both hue and saturation. This together is called the phase.
One thing you’ll notice when you play around with these settings is that they are often very subtle, and don’t allow you to go ‘all out’ like color grading applications do. Camera manufacturers are mindful that most operators will be using these features in tandem with a waveform (for exposure) and vectorscope (for color) while on the field, under pressure.
Therefore, the key goal is to get the shot in a limited amount of time. Settings that give you greater control also will suck time while you get there. It’s a fine line, and most of these settings are more intended to ‘correct’ a shot than ‘creatively color grade’ it. There’s more than one way to crunch the math, and tweaking a setting for one camera will not yield an equivalent corresponding result in another.
The important takeaway is that there is no one correct value or parameter for any of these settings. If there were, the manufacturer wouldn’t give you the option to change it. Think of it as tuning a guitar. Some do it with generic equipment, others do with with specialized equipment, and yet others do it by ear. You do what feels right to you.
I hope this simple primer will help you deal with these video settings in your own cameras.