Archives
Lighting and Exposure
So far, we have covered the basics of composition, and focal length. We can now put an image together that is appealing to the viewer, but when we press the shutter button, all of the detail in the sky is gone. Or, the sky looks wonderful, but all the color and texture in the field is gone. What the heck is going on here? Exposure, that is the culprit here, and is responsible for ruining an otherwise stellar picture.
Exposure must be looked at in two parts: Existing lighting, and how the camera captures that light.
Lets look at the existing light first. This is the easiest and the hardest to master. The human eyes have a much wider latitude when it comes to dealing with extremes of light and dark. Pick any summer day with a bright and hazy sky, look outside the window. You will be able to see detail in the trees, and other objects in the shadows. A camera can not do this at all. To get any detail in the ground, the camera must overexpose (blow out) the sky. This leads to a visually awkward picture with a featureless white blob in the upper portions.
When shooting outside, it is imperative that you pick the time of day and conditions just right. The generally accepted golden time of photography is from sunrise until around 10am. On the other end of the day, look for about two hours before sunset, till when the sun goes down. At these times, the sun is low in the sky. This does two very helpful things. First, the lighting is much warmer because it is lower in the sky and must travel through the atmosphere at an angle. The diffuses the light and decreases the intensity of the sun. This is what allows you to look at a sunset in near comfort. The second advantage to this time of day is the side lighting. When compared to direct overhead lighting, side lighting gives a sense of depth to the scene, and brings out any textures. Combine this flattering side lighting with the warm qualities of a low sun, and you are almost guaranteed a pleasing color tone.
When setting up a photograph, think about the light and what would be the best light to have. There have been many times I've passed by a location because there was nothing special about it, only to return a few hours later and be amazed. It is a good idea to carry a compass with you so you know where the sun will be at the beginning and end of the day. This way you can estimate what side lighting will be available, and determine which part of the day would be the best.
Sun Kissed Photo Copyright © 2006 G. Kiser
In this particular shot, the sun was rising to the left causing the shadows to appear on the right sides of the hills. This gives the mountain range depth, and adds interest to the picture. Also notice the warm light of the scene.
OK, we now know what times of day are the best to shoot, and we know how to plan these photographs around the best time frame. Now comes the technical end of things...setting the exposure in the camera.
Most everybody has an auto exposure camera and has never given it another thought. I challenge you to have some input into what the camera decides for the picture. When I began taking photography seriously, I moved out of the full auto modes on cameras. I wanted to make my own choices in how a scene was represented. I didn't think that the camera knew what I wanted in a picture.
"But I have the best camera that they make, it has auto everything and takes great pictures..."
Something that you have to understand about camera metering systems is that they all work under the same principle. They meter to get the average tone in an image to represent as an 18% mid tone. This is perfect if the scene you are shooting is primarily a mid tone, but we all know that the world is not perfect like that. There will be shadows, and highlights in our pictures that must be dealt with. This is where taking control comes in.
You must know what a mid tone is first. An 18% gray card is just that, a mid tone. It is a non-reflective card that you place in the intended light and meter from it. Once the exposure is locked on that card, you are good to go to shoot in that specific light. The only problem is, for landscape shooters, our subject might be 300 yards, or more, in the distance, not exactly practical to walk that just to set a card down.
As a replacement for the gray card, you can use the blue Northern sky, the green grass, bricks, and some concrete. Pretty much anything that has a middle tone between light and dark. You can meter from these surfaces and achieve the same result. The best way to do this is to set your camera for either spot, or center weighted metering (see your manual). Place the cross hairs +, or selector box [ ] on the subject you are metering from and press the exposure lock button (EL). If you don't have an exposure lock button, find a surface at the same distance you wish to focus and press the shutter button half way down. This locks both the focus and the exposure. Recompose the picture and complete pressing the shutter release.
For those that want to go a step further, you can switch to either program mode, or manual mode. In program mode, you can adjust the exposure value (EV) up or down in stops, based on what you are metering from. In manual mode, you can adjust either the shutter speed or aperture to adjust your exposure. In these modes you have the ability to set your exposure from any number of things as long as you know how you want them exposed in the final image. Here is a chart that you can use.
+2 1/2 stops open textureless white
+2 stops open extremely light
+1 1/2 stops open light light
+1 stop open light
+1/2 stop open dark light
0EV Meter reading medium
-1/2 stop down light dark
-1 stop down dark
-1 1/2 stops down dark dark
-2 stops down extremely dark
-2 1/2 stops down detailless black
(From John Shaw's Landscape Photography)
Using your spot or center weighted metering system, you would aim towards an object and assign it a tone from the right column. Then you would adjust your exposure value (EV) or shutter/aperture value to give you the value from the left column. For example, if you were metering a snowy hillside, the meter would assign a value of 0EV to the snow which would be a middle gray to the camera. You would adjust the exposure value 1 1/2 - 2 stops up (EV +1 1/2 or EV +2) to render the snow a light light, or extremely light tone. With this method, you have complete control over how a scene is portrayed in the final image.
Fog In The Valley Photo Copyright © 2006 G. Kiser
In this photograph, I metered the bright part of the sky, and determined how I wanted it represented in the final image according to the above chart. I adjusted the shutter speed accordingly,and essentially underexposed the picture (EV -2/3) based on what the internal meter told me originally. This was how I chose the image to be captured, not how the camera thought it should be captured.
Another way of dealing with exposure is to use a histogram either in review of your images, or using a live histogram while setting up the shot. This is basically a graph that a digital camera has that evaluates how the pixels are dispersed in the image. The left side is dark, while the right side is light. The middle of the graph represents the mid tones. Try to keep the pixels from bunching on either end for proper exposure. For more detail on the use of a histogram, please visit The Luminous Landscape.
There will be times that the sky is just too bright to be able to keep the exposure where you want it. To keep detail in the sky, you are forced to underexpose the ground. To keep the ground properly exposed, you have to overexpose the sky. In these situations, you need to use a split (either hard edge, or gradual) neutral density filter. There will be more on this filter in an upcoming installment of Tips and Trick. Basically, it reduces the exposure by 2 full stops at the top of the filter allowing you to keep detail in the sky and properly expose the ground.
These are just some things to keep in mind while out shooting those beautiful fall leaves over the next month. Happy shooting!
Written by Greg A. Kiser
radar446 at 2:28:00 PM EST Blog about this entry |
Add to del.icio.us | 
digg this
-
Just found your lighting side bar so no need for further info, thanks
Nancy
5/31/08 5:32 PM
http://journals.aol.com/bgilm