Lets start with a quick review of part 1 from last month.
We discussed the fact that in the opinion of your light meter the world is 18% gray and proper exposure renders it as 18% gray. (Hand modeling by Anne Marie Koschnick)We talked about the difference between incident and reflected light metering.We briefly touched on the idea that you might not agree with your meter’s opinion of the world. So now in part two lets expand on that.
Some times when subjects are deep in shadows, you meter thinks they should be brightened up. In this shot it was late afternoon and the deer was mostly deep in shadows with only a small portion getting lit with direct low angle sun.The shadowy parts were truly lightened up to the point that it looks like mid-day, but the little bit getting sun was over exposed and washed out. I switched to manual exposure and set shutter, ISO, and f stop based on what I thought would be a more realistic representation of the scene.The image is much darker – but then the actual scene was pretty dark with only the small portions of the deer in the sun standing out. Some might argue that this is too dark – and that fine – we all have different tastes, including the engineer that programmed the light meter. Think of this as exposing for the highlights and letting the shadows fall where they may.
Back lit subjects are often grossly under exposed – sometimes rendered as a silhouette. Like this Green Heron in a tree with bright sky behind him.I dialed in two stops of over exposure to get this version.Some might say why not just correct in Photoshop? Photoshop is a wonderful tool and can allow you to create images that your camera just can’t capture but when possible it’s usually a good idea to get as close to what you want in camera. Why? Well look at this Photoshoped version of the original heron image.It’s brighter than my in camera exposure compensation but look at the digital noise. This is a common result when you have to resort to Photoshop to make too big a change to exposure when you and your meter have a disagreement.
How about sunrise and sunset images. Here’s a sunrise exposed as the meter felt was correct.It’s a lovely image but the meter’s effort to lighten up the shadows has reduced the intensity of the color in the sky. Here is is 2 stops under exposed.I find that when attempting to capture color in the sky that under exposure increases saturation.
Let’s talk about stitched panoramas for a moment. If you put your camera on a level tripod and take a series of image with the camera moved along a horizontal arc for each image, you can then stitch them together to form one continuous panorama. For example, this view of Cohoes from Peebles Island is such a stitched panorama.When shooting the series of images it is important that the exposure stay constant across all the images. So, what I do is pan the camera across my subject and watch the indicated shutter speed change as I pan. I note the range of shutter speed and select what I think is the best compromise and change to manual and set that shutter speed. Think that’s going overboard? Here’s a stitched image not shot in manual. I was walking with my camera set to capture quick images of wild life. The black top of the bike path was very shiny as a light mist was falling. When the groundhog bolted I panned with him firing off about 7 frames. I did not shoot with the intention to stitch them together but decided to play with them just to see what would happen. The exposure shift from frame to frame is quite evident.Just as an exercise in using Photoshop I tried to get approximately the same exposure across the images and restitched to get this.Better but no where near what you would want in an image worth framing for your wall. A couple of days later, when it was dry, I saw a ground hog near the same location. I switched to manual exposure and moved in, ready for him to run. This time the images stitched together without needing any real manipulation.I call this “Get Along Little Hoggie”
By now it should be evident that there are good reasons to ignore what your meter thinks is the proper exposure. Let’s talk about how to do it. I thought about including images of camera buttons, menus, and displays but decided that there is enough variation on cameras currently available that it might just cause confusion when you go looking for a Nikon button on a Canon camera, etc.
First let’s talk about a camera setting that really isn’t so much as over riding the meter as it is refining what the meter is looking at. As far as your specific camera, my best advice is “Read The **** Manual.”
Most cameras have several metering modes including an average of the whole scene – a center weighted mode – and spot metering. The first two should be pretty clear but spot metering lets you select a small portion of the image, often a 1 degree wide angle of view somewhere in the image. This would let you select what you really want exposed to a standard “correct” exposure. It can be tricky to use as slight drifting off the intended spot can greatly change exposure in undesired ways. As said above, dig into the manual to figure out how to set various metering modes on your camera.
Exposure compensation is a method to tell you camera to change the meter’s recommended exposure by a finite amount in a particular direction. For example, for back lit birds against a bright sky start with about 2 stops over exposure. Experiment and adjust accordingly. On many cameras there is a button and thumb wheel sequence to dial in such compensation. On my Nikon camera bodies I push and hold the button with the +/- symbol and turn the read thumb wheel. On the top display panel this will show a number with a plus or minus in front of it. The number is in f stop equivalents and often is in 1/3 f stop steps. So as I turn the wheel I will see something like 0.0 +0.3 +0.7 +1.0. +1.0 adds one full f stop of exposure. What gets changed as a result of dialing in compensation depends on the selected exposure mode. On Nikon cameras aperture preferred mode is designated by an “A” (I think Canon is “Av”). In this mode the aperture is held at whatever you have selected and the shutter speed is adjusted as you dial in compensation. In shutter preferred mode (“S” on Nikon cameras) the shutter speed you selected is held constant and the f stop is changed by dialing in compensation. So when we talk about stops of compensation we are talking about adjusting exposure by an amount equivalent to f stops but we may not actually be adjusting the f stop. Confused yet? On Nikon cameras when you dial in exposure compensation a scale will appear in the data area of the viewfinder and on the top display. It mimics an old light meter scale with proper exposure in the middle designated by a 0 and little tick marks appearing on one side or the other to indicate 1/3 stops steps away from what the meter thinks is correct. Again read your manual for details.
If you switch to fully manual exposure you have to set both shutter and aperture. The meter scale mentioned above is used in Nikon cameras when in manual mode. So if your shooting in manual and you want to dial in some exposure compensation you don’t have to push the +/- button. You just change shutter or f stop as desired. On a lot of Nikon cameras there 2 thumb wheels. One on the front of the body and one on the back. The front wheel adjusts f stop and the back wheel adjusts shutter so you can dial in compensation with your index finger on the front wheel and your thumb on the back wheel while looking through the view finder.
Which of these two methods you use will depend on the type of photography you’re doing and what you’re most comfortable with. They both work just fine. Since I tend to shoot landscapes and wild life where depth of field is important to me, I often have my camera in aperture preferred mode and so I use the +/- button for adjustment in most situations. If I’m shooting birds in trees I typically set my f stop to f/11.0 dial in +1 or +2 exposure compensation depending on how bright the sky looks and set ISO high enough to keep my shutter speed in the 1/500 to 1/1000 second range.
Not sure how much compensation you’ll need? Try bracketing. Again most DSLR cameras have the ability to dial in bracketing. You can select how may frames to use, the f stop equivalents to adjust when stepping through the selected number of frames, weather to make the adjustment on both sides of a correct exposure of just on one side. That is I can say shoot three frames; one normal exposure, one over exposure, and one under exposure. Or I could decide to do three frames; one normal, one one stop under, one two stops under. Or I could make all the steps over exposure. So if you’re not sure how much compensation to dial in you could simply bracket the exposure and select the best resulting image. Bracketing is also useful for scenes where the brightness range is too large for your camera to capture. With the camera locked down on a sturdy tripod you could bracket the exposure and then in an editing tool like Photoshop you could merge the multiple images into one with a technique called HDR (which stands for High Dynamic Range). There are some newer camera on the market that can do HDR in camera.
This completes the discussion of the basic in camera adjustments that affect exposure. Next month in part three we will talk a bit about selecting and/or modifying the light source to get the exposure you want.