Perfect Exposure vs What The Eye Sees

[EchoingWhisper]

What do you recommend? A perfect exposure (and white balance) based on the grey card or an exposure (and white balance) based on what the eye sees?

 

[The_Traveler]

This is a tricky question because the answer is always;'it depends.'

If the situation is stable - posed shot, no lighting changes - and the scene is homogeneous - a good range of tones and the center of itnerest not too bright or too dark - then grey card exposure works great.
If the lighting changesd from moment to moment, the scene is made up of large blobs of light areas and dark areas out of a comfortable range and the center of interest is either much brighter than the average or much darker, then I alter what the camera suggest to get the result I need.

Lew

 

[EchoingWhisper]

What the eye sees?? Here...click the link below to see what the eye sees...

Checkershadow Illusion

As stated by the explanation for the above "illusion," it's a measure of the sucess of our optical systems, rather than a flaw. One of the more problematic image senarios is the indoor shot with a bright sunny day on the other side of a window. When we see the scene with our eyes, we clearly see the outdoor scene through the window, and we also see a well lit interior. When we take a picture, however, the window is very bright and the interior is very dark. So is this a dynamic range issue with the camera? No it isn't. The camera scene is accurate. Our eyes can recognize the difference in luminance and lift the shadow areas to make them brighter. It's an automatic gain system that we have no control over. When we look at the image produced by the camera, our eyes do not perform the same type of gain. That's because the imaging system is representing luminance levels with color. That is to say...a white lampshade in shadow in the room interior will be represented by the color gray. In the live scene, the shadows are lifted and we can tell that the lampshade is supposed to be white. In the picture, we see the gray color for what it is...gray...and so our eyes do not apply any gain to the dark areas of the image.

This is why post processing is still more art than science. The human visual system is infinitely variable, and so each image must have its brightness levels tuned "by eye."

As for white balance...I have two guidelines. If the color of the light is a feature of the scene, as in sunset or candlelit scenes, then I use Daylight white balance and tweak by hand if necessary. Otherwise, I find that a custom white balance always looks best...better than anything I've been able to do by eye. For the reasons above, the eye is a horrible calibration tool. Along with auto gain, your eye has auto white balance, and your eyes are actually changing as you work on your image. That's why we have hardware for calibrating monitors, and custom WB processes. If we could set WB by eye then we would be able to calibrate a monitor by eye...but we can't.

Thanks for the white balance tip.

 

[KmH]

There is no 'perfect exposure'. The camera cannot reproduce what a human eye sees, for 2 reasons: 1. The camera can only record 2 dimensions. 2. The camera can only 'see' light linearly.

Just about any scene will have brighter and darker areas and what the human eye sees is not-linear. Consequently, you can accurately expose for brighter, or for darker, but not for both.