Sky/Light questions

[Camerajunkie]

OKay, I have a couple of more questions I'm hoping you all can help me with. I'll use two pictures to illustrate. The first I was trying to capture the sun hitting the trees and making them do the "green glow" thing. That didn't turn out quite right.

http://i130.photobucket.com/albums/p269/CamerajunkieD50/DSC_0080.jpg

Pretty good but not that effusive glowing...

Then the 2nd one was a very pretty shot, green glowing on the sides and the blue, blue sky. Sun was to the left and it pretty much blew out most of the sky. How do you NOT blow out the sides, get that gorgeous blue, and still have the green glowing from the trees?

http://i130.photobucket.com/albums/p269/CamerajunkieD50/DSC_0089.jpg

[ktixx]

For a vibrant blue sky, the best bet is to use a polarizer, however to get the "perfect" picture, where all areas are nicely exposed, you need to use multiple images and blend them together. Digital photography has made this much easier to do, with programs like Photoshop CS2 - merge to HDR (http://www.luminous-landscape.com/tutorials/hdr.shtml) and Photomatix (http://www.hdrsoft.com/). Now all you have to do is snap 3 or more pictures, one exposing for the highs, one for the mid's and one for the lows (ie: one for the sky, one for the tree's and one for the shaddows) - this way you will have the Highest Dynamic Range (i.e.:HRD)
Ken

[Prospero]

The problem with cameras is that they have a limited dynamic range. The typical outdoor scene contains a lot of different light levels, and your camera is only able to capture a small portion of that.

In practice this means that in some cases it is not possible to get a picture which has both the shadows and the sky well exposed. In the second shot, for instance, you could have underexpose the picture by 1 to 2 stops to regain the sky, but that would have meant that the green trees are close to black.

So what can be done about this:

1. Filters
Using a graduated neutral density filter you can make the sky darker and thus the foreground lighter. Such a filter consists of two halves, a dark and a bright one.

There are two types of graduated neutral density filters, soft-edge and hard edge. Soft edge can be used with uneven horizons and hard edge filters are best with level horizons. Still, no matter what filter you chose, the horizon must be relatively straight. Tall trees in the foreground will mean you cannot use such filters.

2. Underexpose and brighten in PP
This is a technique I use a lot. Mostly I expose my shots in such a way that there is no part of the sky blown out. Then, using D-lighting and control points in Capture NX, I brighten the foreground. Sometimes I'll darken the sky a bit more to enhance the picture.

The main disadvantage of this technique is that raising the brightness of shadows may result in extra noise.

3. HDR - Exposure Blending
In my opinion the best technique, but also the most difficult. What you do here is take several shots of the same scene, each with a different exposure value. I usually take 7 shots ranging from -3EV to +3EV. These shots are then blended with HDR tone-mapping software, for instance Photomatix. Often they require a lot of adjustments after that to make the pictures look convincing. This week I'll write a tutorial on this forum about HDR, I'll give more information on how everything works there.