Following on Artie's post and the thread drifting, at jays suggestion I thought we might start a new thread. This one dedicated to the angle of light between you, the photographer, your subject, and the light source (often the sun).
I have looked at a number of bird images on BPN and see some trends. I'm pulling out examples, mostly of white birds (or birds that have a lot of white) because you can see the effects of light angle more consistently. Please try and not be offended if one of your images shows up in the too flat category. If you went through my bird gallery, you can also pick out images that I would put on this (too flat) list.
Phase angle is the angle between you and the sun as seen at the position of the subject. If your shadow points directly at your subject, there it little to no angle between you and the sun: the phase angle is near or at 0 degrees. Example, the full moon. Subjects lack shadows, but more importantly, the shadows are lacking in the fine details, e.g. the feathers on a bird, or the grains of sand on a beach, or the grain in a stick on a bush.
As phase angle increases, shadows start to form. On curved surfaces, the light intensity drops, giving subtle shading and that we perceive as form in images. The subtle shading makes a 3-dimensional object look more 3-dimensional in a photograph (which is always flat).
At very low phase angles, there is first surface reflection from the components making the subject, and first surface reflections have little color. As phase angle increases from zero, the first surface reflections decrease and color actually increases. This observation is for complex surfaces, like rocks and soils, tree branches and leaves, skin, hair, bird feathers, etc. it doe not apply to surfaces there there are large flat surfaces, like windows or calm water.
As phase angle continues to increase, shadows become deep and images can become very contrasty. High contrast interferes with our perception of color and can push the limits of the recording medium (film or digital sensor).
At high phase angle (approaching 180 degrees), the sun is behind the subject. Things that are small or similar to the wavelength of light scatter light a lot. For example, dust in the atmosphere, a cloud, or a person's hair. This is called forward scattering. Some subjects are translucent and let light shine through, for example, leaves in the fall, or light through a bird's wings. Usually, this transmitted light has greater color than reflected.
These effects are all well explained by the physics of light called radiative transfer.
BPN posted image that look too flat in my opinion due to a low phase angle:
Wonderful light off to the right, showing detailed form, beautiful! If the light were straight on (point your shadow at the bird) the image would not display the subtle forms and would lose its impact. (Image by Arash Hazeghi).
White-tailed kite. http://www.birdphotographers.net/for...read.php/79164
This is a portrait of a sandhill crane with a phase angle of 20 to 30 degrees by Troy Lin. The image shows wonderful form, texture, and color with great light.
*Sandhill Crane Close Up * http://www.birdphotographers.net/for...Crane-Close-Up
Here is an image with nice feather detail by Artie. The sun is off to the left about 20 degrees. We see a small shadow of the wing on the bird's body. I think the feather detail would have been a little better if the sun were another 10 degrees (about) further to the right.
Nice Reflection..... http://www.birdphotographers.net/for...read.php/80944
BUT compare the above image to image in the first section. the same species but near zero phase angle:
Squacco Heron low phase angle: http://www.birdphotographers.net/for...read.php/78168
Note the major difference in feather detail in the wings!
The sun was above Artie when he made this image, but the phase angle looks to be about 20 to 30 degrees. The phase angle helped make the nice feather detail. From the direction of the feathers in the wings, if the sun were to the right the same phase angle, the feather detail would have been even more intense. Even so, the phase angle works well here.
Blessed by the Sun http://www.birdphotographers.net/for...read.php/80869
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Phase angle probably too high (subject side mostly in shadow):
I couldn't tell what the phase angle was on this one, but the feather detail is astounding.
Perhaps diffuse, overcast light, which is indicated by the discussion.
Non-Baited Dalmatian Pelican :) http://www.birdphotographers.net/for...read.php/81061
After reviewing these images, try imaging with the sun at different angles. What angles do you like best?
Roger
Last edited by Roger Clark; 03-16-2011 at 06:23 PM.
The angle of light and image impact
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