As the photographer, your task is usually to decide whatâ€™s most important and then compromise on the exposure accordingly, based on the various elements in your scene.
Hereâ€™s a typical situation: youâ€™re by a lake. It’s late evening and the sun is setting.
The warm sunlight is coming off the water and at an extremely low angle.
Your subject is bathed in beautiful warm light but one side of her face is in heavy shadow.
Your camera meter suggests 1/250 sec at f8 at ISO 100.
You whip out your trusty digital SLR and you shoot your picture hopefully you’re shooting on manual.
This is the best mode to shoot if you want to master your digital SLR.
Manual mode allows you to see the metadata of each picture you take so that you can troubleshoot when things go wrong.
Automatic, aperture, shutter and program tells you nothing if things go wrong so you won’t be able to learn how to correct your picture-taking mistakes.
You look at your efforts and you see the picture above. One side of her face is underexposed, but the other side looks perfect at least on the little LCD monitor.
What your eyes see in the monitor depends on how bright the ambient light is. I’m sure you’ve been burned at least once trusting your eyes as they look at an image right after you take a picture.
So the more reliable method is to enable the histogram view in the LCD and learn how to interpret that.
You may have heard this next piece of advice somewhere.
Move in closer and fill the frame or viewfinder with your subject.
This gives your camera a better chance of getting an accurate reading.
This time you fill the frame and the meter suggests 1/250 sec at f5.6 at ISO 100.
That is an increase in 1 f-stop of exposure i.e. opening the aperture from f8 to f5.6.
Your next picture shows an improvement, or does it really?
Now you can actually see the shadow side of your subject better.
But there is a down-side.
Her face closest to the light is now so over-exposed, you can’t see any detail in the highlight area.
Face it, you have to choose between losing detail in the shadow side of your subject’s face or highlight detail.
You have 2 options.
- Boost the shadow side with a reflector or a flash
- Have your subject turn so that both sides of her face is lit more evenly by the light.
Typically at this late hour in the evening, you have to work fast because the sun is setting and the light levels drops quickly.
So why did you choose a shutter speed of 1/250? The foremost reason is: 1/250 sec is the highest shutter speed our camera will sych with our flash units.
This shutter speed may vary from model to model but the typical highest sync speed whether it is a Nikon or Canon camera these days is 1/250 or 1/200.
You could use the equivalent exposures of 1/125 at f8, 1/60 at f11 and 1/30 at f16, but why would you? This is a portrait situation and you want the background to be as blurred out as possible.
Besides, our mnemonic device, Seasoned Apples Smell Nutty to Blushing Bachelors, tells us to â€œSet Aperture to Small Number to Blur out Backgrounds.â€
And to compensate for that large number f-stop or aperture, you should use your longest lens.
If you take a picture with a telephoto versus a wide angle lens, you will find that the longer focal length lens blurs out the background more than a wide angle lens.
Using the the built-in flash
So after selecting your lens, you now decide you like the pretty warm light that you see on your subject.
To maintain that â€œlook,â€ you will have to supplement or fill the shadow side of your subjectâ€™s face.
A reflector is perhaps the easiest fix if you have someone to hold it for you as you shoot.
But unless you know beforehand that you’ll have an extra set of hands, the more practical thing to do is to use flash.
Most consumer grade digital SLRs like the Canon 20d, 40d, Rebel XTi or Nikon D40x, Nikon D200s have a built-in flash that pops up. They remind me of a crabâ€™s eye.
To turn them on, you usually have to switch the camera to â€œManualâ€ mode, then press a button somewhere.
On the Canon digital SLRs, that button is located near the red dot of your lens.
When your little flash pops up, all you have to do is compose your picture and fire away.
- For those of you who want even more control, you can try this:
- Push the button to illuminate the LCD panel on the top of your camera.
- Press the Flash exposure compensation button.
- Dial in the amount of fill flash you want. This is just a fancy way of telling your camera flash how much light â€œto kick into the scene.â€
If you want to overpower the ambient light by one stop, turn the Quick Dial on the back of your camera clockwise or to the right and the flash should overpower the ambient light setting by 1 or 2 stops. You can fine-tune this in 1/3 stop increments.
The picture taken with just available light.
The picture taken with fill flash. The highlight region on her hair is blown out a little but it’s an acceptable compromise. In this instance the flash was set on default which means the flash is programmed to kick in the same amount of light was the ambient light source coming in from the left. This ratio where both light sources are equal is 1:1.
The camera figures out that how much power the flash needs to put out to fill the shadow side of the face keeping in mind the default setting is equal amounts of light or 1:1.
The picture above without fill flash is not too bad but if you were to print it, youâ€™ll see that you canâ€™t see your subject’s face thatâ€™s in shadow.
On the computer screen, it looks alright but trust me. What you see on your monitor doesnâ€™t always print because it is beyond what is reproducible on print.
The picture shot using the built-in flash on automatic or the default setting will print very nicely because the range of the brightest highlight to the darkest shadow has been narrowed.