Monitors:

Color monitors are close cousins of color TVs. Have you ever noticed the wide variety of color and brightness that people set on their TVs? Just look at the line up of TVs in a store. Some people like the colors saturated, others don’t; some like high contrast, others prefer low contrast; some like the picture bright, others dim. Of course all the combinations of these are used given the wide variety of personal taste in the world. Most modern computer monitors don’t have user color and tint controls like TVs, but they do have brightness and contrast. There are a wide variety of phosphors (the stuff that emits the colored light) used in the various monitor’s CRTubes. Combine this with the numerous manufacturers at any price you want to pay, the wide range of age in the monitor population, and it starts to become clear that getting people to see your picture the same way it looks to you is going to be at least a challenge. Now sure, there are high performance monitors available that will allow people to work on photographs so they have a good idea of what there result will look like, but these are usually used in a closed sort of system. For instance someone is preparing photos for printing in a magazine. They know the performance of the inks they use and how to relate that specifically back to what they see on their computer screen; at least to a degree. It’s interesting to note that in even this sort of closed sophisticated environment that they often, if not always, make proof prints to check the results before they actually commit to run the presses. So there you are, you’ve got a digital image you want to send to someone in the e’mail. Is their monitor the same make and model as yours? Do they keep their contrast and brightness set the same as yours? Back in the viewing section I brought up the point about how a picture looks depends on what light is shining on it. Monitors make their own light; they don’t need an external light source for the picture to be seen. However, the ambient light around the monitor WILL interact with the light the monitor is producing and change the apparent color and tone of the displayed image. Try it; you may be surprised at just how much difference it makes. Professionals usually work with their monitors in rooms that have white or shade of gray walls and indirect lighting that is not allowed to shine on the monitor screen. In fact they often put a shroud around the screen. Now you may not care if the color and tone are accurately represented the same way as you saw them, but if you do just the difference in monitors and lighting can be a real challenge.

Monitor driver (video) boards:

There are also a wide variety of video boards in use. While it’s fairly safe to assume that it’s VGA, how much memory does it have? How is a given board set up to use it’s memory 640 X 480 X 256 colors? or one of the many other combinations that are possible depending on the persons monitor, video board, memory on the video board, and how the computer was set up. So you’ve got your fine image you’ve slaved over to make it look perfect on your monitor. Your feeling very happy as you make your JPEG file with tons of pixels and millions of colors. The person that ends up with your nice picture has a monitor set up like the one above; they won’t see what you saw, not by a long shot. It’s probably Okay; just be aware that it will be a rare thing that someone else will see what you saw.

What can you see on your monitor?:

The strip below is a series of gray patches. The values for Red, Green, and Blue content of each patch are equal (that’s how you get a neutral gray) and the number they are set to is above the patch. This number can have a range of 0 to 255. Can you see the difference between adjacent patches? or do several patches in a row all look the same. There are lots of things that go into the result you observe. The capability of your monitor, how you’ve got it adjusted, how your video driver board is set up (number of colors etc.), and your personal visual sensitivity. Another interesting point here is that even though these patches were created with uniform pixels of the values shown. If you have a tool that will allow you to analyze this image you will quickly find that several pixels have gone astray. So much for loss-less compression. This JPG file was made at a compression level of 15. In this case the image still serves its purpose.

Now, just for giggles, take a look at the same sort of scale, but the first one is red only, then green only and finally blue only.

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