You may see a beautiful morning scene, trees illuminated softly with sun's light and a sky full of colorful clouds.
You want to take a picture of such moment, and if you don't understand this concept, you will find yourself in one of
You may see a beautiful morning scene, trees illuminated softly with sun's light and a sky full of colorful clouds.
You want to take a picture of such moment, and if you don't understand this concept, you will find yourself in one of these scenarios:
- Your shot comes out underexposed since you didn't use a slow shutter speed, you thought light was enough for 1/40 and it turns out you needed a 5 seconds exposure.
- The trees come out properly exposed but the sky is blow out.
- The sky came out properly exposed but the trees are underexposed.
By the time you get it right, sun has come out completely and the clouds are white now or gone.
The crucial difference
The subject of why what your eye sees is not what your camera sees is not exactly a simple one, there is a lot of science in between, however, I will give you the facts you need to know to understand it.
In a simple statement, the main difference between the human eye and a camera sensor is that the human eye can perceive a wider range of light than a camera sensor does.
So what does that mean?
Your eyes can perceive light in a way that you can see details even when your subject is illuminated from behind, or in scenarios where both the front and back planes are illuminated, your eyes can see both planes properly.
A camera sensor can not do this. If you took a picture of someone while being back lit, you would need to add light to the picture so the camera shows the person's face, in this case you would need to use a flash.
In the example of the first section, either you have to pick between the trees or the sky, but you can't get both.
Another good example would be while you're indoors. Usually you can see your way around inside a building pretty well, but a camera can't, in practical terms, it would be blind.
If you took a picture from inside a house at noon, you either properly expose the inside and have a blown out, practically white outside OR you get a properly exposed outside while the indoors look like a cave.
For explaining purposes, lets imagine a scale from 0 to 100. 0 would be really REALLY dark and 100 would be really REALLY bright.
In that scale, a human eye could perceive from around 20 to 80/85, while a camera sensor could perceive from 40 to 70/75.
It's not exactly a scientific scale but it gives you a notion of how much difference there is.
Mr. Gary L. Friedman explains this concept in his books for the Alpha DSLRs in stops. A stop would mean a factor of 2 in light intensity.
He uses the following examples:
Photographic paper: 6.5 stops
Digital sensors: 8 stops in JPEG, 10 in RAW
Color negative film: 12 stops
Human eye: 30 stops
Source: The Complete Guide To Sony's Alpha 700 Digital SLR Camera And The Alpha Mount System by Gary L. Friedman
This explains it in photographic terms, the human eye can sense a lot more light and shadows than a camera can. When a camera sensor goes beyond its range e