BetterPhoto Q&A
Category: New Answers

Lighting Problem

To love this question, log in above
July 12, 2008

To love this comment, log in above
July 12, 2008

The fact that white walls reproduced with a hue in a flash shot is the norm.
Allow me to explain:

We see via our human eye brain combination. White walls and other dominate expanses of near neutral hues are often perceived as neutral because our eye/brain combination instructs our eyes to effect a visual adaptation and change sensitivity to colors. In essence, we involuntarily “white balance”. This is both a mental and a chemical process (we secrete the sensitizing chemical rhodopsin) color balance changes happen in a split second.

Additionally, our perception of the colors about you are based on the color of the illuminating light. Indoors, this illumination is likely ruddy tungsten, or a greenish-blue fluorescent, or perhaps other weird combination. When your flash fires, your camera sees the subject bathed by daylight hue of the flash. You on the other hand are adapted to the colors of the ambient illumination. In other words, you have never seen the colors of the subject as they might appear illumined by daylight source.

Also, consider that paints and fabrics often fluoresce when hit by UV light. An electronic flash is rich with UV. Stated a different way, often whiteners and brighteners are added. Under electronic flash they take on a bluish or greenish hue.

Alan Marcus (dispenses marginal technical gobbledygook)
ammarcus@earthlink.net

To love this comment, log in above
July 12, 2008

To love this comment, log in above
July 12, 2008

You can prove to yourself that the human eye/brain carries out involuntary “white balance”. Please treat yourself by performing the following experiment.

Obtain several strongly colored filters (not neutral). No filters? Locate colored cellophane gift wrapping etc. Arrange before you, strong red – green – yellow filters etc.

Sit facing a bright lamp. Hold one of these colored filters up to just one eye. Stare at the bright lamp through the filter for a few minutes, remember, you are filtering just one eye.

After a minute or two, quickly put down the filter. Now look about the room with both eyes. Quickly cover just one eye, use your hand or a card. Speedily alternate your hand or card, cover the left eye and then switch, now cover the right eye. Alternate your covered eye. Enjoy the alerted color balance view.

This is a powerful experiment that reveals the influence of the human eye/brain adaptation mechanisms.

What is happening? The human eye has three receptors red – green –blue. The brain controls independently the sensitivity (ISO) of each receptor system. While staring at the lamp through the red filter, the eye/brain recognizes the color it senses is abnormal. The eye/brain changes the ISO of the filtered eye. The unfiltered eye is not adjusted. Now when you look about, without the presence of the filter, you see the effect of the adaptation. Because this adaptation happens to just one eye, you can now see the differences as you switch views – left eye than right eye.

Try this experiment – you will never regret having seen this amazing mechanism.

Alan Marcus (margin technical gobbledygook)
ammarcus@earthlink.net

To love this comment, log in above
July 13, 2008

In Auto mode, when flash is called for, most camera’s chip logic automatically switches to flash with balance approximately 5500°K.

Alan Marcus (more marginal technical gobbledygook)
ammarcus@earthlink.net

To love this comment, log in above
July 13, 2008