# Introduction

The hardware you use to create your images will influence the final result you perceive. Also what the audience uses will change the impression they get. How many times have you thought the image was OK, and someone said it looked too dark or too bright in his computer? So we will try to understand what happens, then you can better choose and configure your own hardware, and advise viewers on what they should do with theirs, for better transmission of your idea, be it video or still image.

# Video Cards

Modern computers work in RGB, Red, Green and Blue, as with those three components a wide range of colours can be created. For each component, the computer stores a given value, how much of Red, for example, from minimum to maximum intensity. Being digital devices, it has to store such information in zeros and ones, in binary, and it has to choose a limit of how many digits to use.

## Bits

When you look at video card settings, you will probably see 16 bit, 24 or 32 bit. That is the number selected by the system to store the information of the components. 16 means typically 5 for Red, 6 for Green and 5 for Blue (in some computers it is 15 bit, 5 5 5). 24 means 8 for each, and 32 means also 8 for each, reserving the extra 8 for Alpha or just wasting them (but as advantage getting faster operations in some cases, computers like to work with powers of 2, and 32 is exactly 2^5).

5 6 5 bits

Green gets the extra bit as human eye is a bit more sensitive to it

Let's take the 24 case, three components, each using 8 bits. And let's focus in the Green channel, with those bits (if you remember a bit of base 2 from school) we can go from the minimum 0000 0000 to the maximum 1111 1111 (separated in groups of 4 so you can easily see they are 8, just that). Converting to base 10, it goes from 0 to 255, so we can represent 256 different levels of Green, from no Green at all to maximum intensity the system is capable of.

Taking into account the combinations of the three components, we can represent 256 * 256 * 256 different colours, 16777216. That is a lot, and practically what the human eye is capable of discerning, but not necessarily in all cases as each person is different. Say you select a colour that has no Red or Green (value 0 in those two channels), just some Blue level like 120, and you will be capable of finding people that notice the 1/256 difference from that given blue to the next blue possible, 121. If we go with the 32 bit setting, we get the same total and same size for the steps, as the extra 8 are not used for the RGB components.

But the 16 (or 15 bit) cases are a bit different, channels with 5 bit allows us the range 0 to 31, thus 1/32 steps, and 6 gives 0 to 63, thus steps of size 1/64. Remember the numbers are different but the idea they represent is the same, they are the maximum. Those steps, being bigger than 1/256, are more visible in general and to a wider range of people.

On some systems, instead of 15, 16, 24 or 32, you will see Thousand of colours (simpler way than saying 32768 or 65536, and less technologically cryptic than 15 or 16) and Millions of colours (instead of 16777216, 24 or 32).

## Simple Example

OK, all that sounded a bit confusing... what about if we think in terms of bulbs? We have to provide the same quantity of light, but you are given two methods, in one we have lots of small lamps, group A, and in the other, group B, we have less but each is more powerful than the ones in the other group. In total, all the lamps of each group give the same light when they are all on, but we can turn on and off just one light from group A, and reduce the light a small step, while in group B that will have a bigger step. So we have more control with lots of lamps, each contributing a small part, than with a reduced number of high intensity ones.

## Recommended Value

With a good CRT or LCD you should see some banding issues in this gradient. With a bad monitor or your card set to 16 bit or less, you will clearly see diagonal bands.

You want to set your card to 24 or 32 bit mode (whichever is allowed or makes the card go faster), to get the biggest number of colours with the smallest steps from one to another.

Also, notice that even in such mode, there are some cases in which you will see problems, and probably will require to enable Dithering option in render output. 24 was a good compromise, but not perfect.

# Monitors

Currently there are two basic families of computer monitor technologies, the tried and trusted CRT, Cathode Ray Tube, and the newer LCD, Liquid Crystal Display.

## CRT

CRTs are analog internally, but are fed from the video card, so in the end are also limited in some way by the bits we just talked about in the video card section. They work, in few words, by launching electrons towards the flat or near flat surface, where they excite the phosphor coating and thus generate light.

Shops only carry the high end ones now (2006), as they have good quality, and for some jobs, size and power usage are not so important compared to other things like well known colour behaviour. Of course, if the monitor is old, low quality or both, you can have the best video card, and it will still look bad.

## LCD

This image tries to compare what happens in 18 bit LCDs (left) and CRTs or 24 bit LCDs (right). To notice the difference you need a system working in 24/32, of course, otherwise both sides will have bands.

LCDs are digital and not all are created the same. The working principle is that a light is emitted behind the glass surface, and by different levels electricity, the glass lets pass more or less light. Those levels are controlled digitally, so we have a similar issue than with video cards, in this case some work in 24 bit and others work in 18. That number comes from 6 bit and 3 components. As already explained, 6 bits gives too noticeable steps.

So if you can find the information before buying, go for the 24 (or 8 bit per component) ones, otherwise you can set your card to 24 but not really see that, as the LCD would be the limiting factor. We could do a huge review of common LCD manufacturing methods and what they mean for the colour quality, but I prefer just to point out that quick detail about not getting a 18 bit one, and refer you to other sites dedicated to hardware reviews, and what is more important: try to see in real life before buying. If possible carry a set of images and videos, then make the salesman show them on the monitors to check how bright, dark, high contrast, low contrast, b&w, etc images look and thus get the best monitor with the budget you have.

# Workplace

The location you use to work will also affect what you see. If you can choose the lighting, go for 5500 K lamps, as they most closely simulate daylight conditions.

You could go with real light, but then you would not be able to work by night and along the day you would notice it changes. After all, we want a stable environment.

Strong ambient light is bad, but do not work in the total darkness either, you want to be able to read papers and see your keyboard and mouse. Get a comfortable setting that allows you to do work on the monitor and also with other things.

Avoid reflections from light sources, build a hood if needed. No, those hoods professional monitors have are not for secrecy, they are to avoid reflections.

# Basic Calibration

Monitors provide some controls to adjust the image. We will try to get the best monitor settings, without requiring extra hardware or complex methods. If you want to do it correctly, which is out of the scope of this document due the complexity, you should get a profiler device (a sensor that measures your monitor output) and the proper software to make the perfect setup.

## Colour Temperature

If you play a bit with your monitor menus, you probably have found something about colour, probably something with numbers like 9300 K or terms like sRGB. Try them, and you will notice how the global look of your monitor changes. Higher values makes the monitor look cooler, bluer, while lower values make it look warmer, yellower. The number is the Kelvin degrees a black body must be to emit that light, and I always found it funny that higher temperature means what we describe as "cooler" colour.

In recent years, the advised setting is sRGB. If your monitor does not provide it, you should try 6500 K, which is part of the sRGB standard. If you do not, or have to show your images on a monitor with different setting, you will see how your colour have changed slightly, getting some tint. If you think the colours look a bit strange at sRGB / 6500 K, give your eyes some time before deciding it looks strange and you must go back to whatever you had before. Go away from the computer, if needed. It will pay off to get used to it, as you will be sure you are going with the neutral setting.

## Brightness and Contrast

Adjusting the brightness and contrast is not about "I like it" but also not too hard. First you need to leave your monitor to warm up, this can take from a few minutes to up to an hour.

Select a black background or wallpaper, so we can compare what the system "paints" as black with the real black you can get. Then set brightness and contrast to the max.

Using the vertical controls, move the display area so you can see "unpainted" parts, if you do not have a border already. Top or bottom borders are good for this, as you can avoid taskbars or menubars, respectively.

Finally, play with the brightness until the background black merges with the unpainted black. Only adjust contrast if you think highlight parts of images are too bright.

That is all, now you should have a monitor using from the best black you can get to the best white. As test, look at the image, you should be able to see all the squares..