The best most accurate painting in the world is merely an interpretation. This is because paint has limitations.
White paint is the brightest that any artist can get, and yet when you look at white paint we are not blinded as we would be if we looked at the sun or a welding arc. Similarly, black paint is as dark as paint can go and yet when we look at it we do not mistake it for the depth of blackness found in a cave.
If we say that real sight has a value range of 1 to 100, (with 1 being the absolute absence of light and 100 being pure white light) then the value range available for paint would be something like 10 to 40.
So, what can the artist do when he needs to represent the world and limitations beyond his control prevent him from doing that?
The artist must translate what he sees or imagines into the value range that is available to him. A good way to begin a painting then, would be to establish the lightest and darkest spots on the canvas first. After your lightest and darkest spots are found you can then make comparisons with all of your other values and build up the range between.
A trick used by almost every artist wishing to get accurate values is the squint method. With natural vision your eyes will dilate to see as much information as they can. When you look at a dark area your eyes will let in more light so you can see better, but since the dilation of your eyes has changed you no longer see the same value difference as you did while looking into the light areas. By squinting your eyes you prevent your eyes from focusing on one specific area and instead see an overall view of the scene before you. This means that your eyes choose an average dilation for both the darks and lights and so you can see more accurate value relationships.
Unfortunately when it comes to paint this means we will have to make hard choices. Sometimes we will not be able to get the exact color we see with our eyes since to make it dark or light enough we will have to sacrifice some of the color’s hue or intensity. This is also why holding up a color in front of a scene to match the color should be used more as a guide than as something to match colors as we will run out of value range long before we can match everything exactly.