Saturday, October 23, 2010

Coping with harsh sunlight

Since time immemorial photographers have been admonished to avoid the noonday sun. Yet morning and evening sunlight, though nicer in direction andLJK_1744-DEMO3-A3 (640x640) color, can also produce inky-black shadows in pictures, that make them almost worthless.

There are ways around this dilemma.

SunPick a setting where lots of light is reflected into the shadows. Think white-washed walls on Greek islands, sugar-white sand on Gulf coast beaches, fresh-fallen snow. Maybe those are not always practical.

SunUse one or more reflectors to lighten up the shade. I like white umbrellas, they are more compact than most professional equipment and lot less expensive. Watch the umbrella display on your next visit to the drug store.

SunTurn on the flash on the camera for fill-in light. Most digital cameras even have a setting for this.

Light bulbIf none of the above are workable solution for a situation, there is post-processing! You guessed the reason I chose a fast-moving kid in bright evening sunlight with the surroundings in deep shade, so the shadows would be dark!

Getting the shadows lighter is easy. Here views of Picasa and Windows Live Photo Gallery in action. Note the red pointers.


In Picasa (on the left) the control is called “Fill Light” – the default setting is with the slider at the left. Moving the slider right lightens the shadows and you can see immediately the effect. In Photo Gallery the control is under “Adjust exposure” and is called “Shadows” (click Fine tune to get to the controls). This control goes both ways, to the left to darken shadows, to the right to lighten them.

Ah, but even here at Café Ludwig there is no free lunch. There is a price to pay when doing this. Let’s take a look at exactly what happens when you “lighten the shadows”. The image consists of individual pixels, each with its own level (really in each color – red, green, and blue). The lower level pixels are changed – amplified – to a higher level. The lowest level pixels, nearly black, are also at the lowest electrical level. There is always some electrical noise in processing signals, the lowest pixels are affected the most.

If the noise is just one bit up or down, that is 1 in 256 for normal 8-bit JPG images, then the bits at level 1 maybe recoded as o, 1, or 2 – a huge percentage. The noise problem gets less for higher pixel values. A pixel at level 10 with this noise would be 9, 10, or 11. Just a ten percent change. LJK_1751-DEMO3-A2

When these pixels are increased in value, so is the noise. Double that level 10 pixel, and the noise is now twice as large. Here is a close-up section of a photo showing the face our athlete. The left side was in deep shadow, the right in full sun. Bringing up the low-end pixels to “lighten the shadows” also brought up the noise. You can readily see that in the illustration.

So there are limits to post-processing “fill light”. Is there help for this? Of course, why else would I ask the question?

When using Windows Live Photo Gallery, Picasa, and other common application the photos are processed in 8-bit JPG format. That means there are 2-to-the-8th, or 256 levels. Most cameras can do better than that, “raw” format is usually 12 or 14 bits deep. That means there are many more levels before the noise is reached. Astonishing improvements can be achieved when using dedicated image-editing applications like Photoshop, Paint Shop Pro, or others of this type, that can take full advantage of what the camera delivered.

For me, well, I will keep my white umbrella handy.