Exercise: Learning the Limits to your Digital Camera's Electronic Flash
Most consumer digital cameras come with a pop-up flash. These are useful, but very limited. A great photograph is made by several factors, lighting being one of the biggest.
Have you ever gone to a concert and saw someone in the nose bleed section using their flash? They may really get a picture, but it will not be because of their flash. Whether your camera is a Point and Shoot or a Digital SLR the flash works the same. Understanding how to use your flash and its limitations will improve your photography.
General Flash Information
Your flash has a maximum output measured by Guide Number (GN) of 11-13 meters at ISO 100. This number determines how much light a flash can produce. The electronic flash can be used for:
- fill-in flash - reducing shadows under the eyes or adding light to a subject which is backlit.
- as a trigger for other flash units
- to provide catch lights in your subjects eyes
- there are 3 main ways to modify the flash exposure effect for a given subject distance:
- change the aperture/f-stop
- change the ISO - sensitivity to light
- change the flash output this can done by adjusting the flash or using your cameras compensation guide.
Changing shutter speeds or switching to an action mode will only affect the amount of ambient light which is recorded. It will make a scene lighter or darker based upon the ambient or natural light and not the flash light.
Using Your Electronic Flash
Full Auto
- Go to a large room or wide hallway without sunlight coming in. The reason I want a wide hallway is that you do not want anything to affect the flash but the subject.
- Place a subject a few feet away from the wall. The subject should be an average subject, not too dark or light, and have texture.
- At a distance of 10 feet take a photo. Does it look good?
- Move to 15 feet and use the camera's zoom to approximate the same coverage. Take another photograph.
- Now move to 20 feet and use the camera's zoom to approximate the same coverage. Take another photo.
- If the image still looks go back up another 10 feet.
If at 30 feet your picture looks good then you either have a great flash or there is enough light in the room for the camera without the flash.
In most cases you will see that as you move farther away you will get to a point where the subject starts to get darker because the flash isn't putting out enough light.
So you can tell where you are on the sequence shoot a picture of the ceiling.
Using Your Electronic Flash - Program Mode
On most digital cameras the full auto mode does not allow you to set the ISO so you will need to go to Program Mode. Once you are in program mode set the ISO to 100 and repeat the exercise.
Take notes.
Now change the ISO to 400 and repeat the exercise.
On most cameras you will see that at the ISO 100 setting there is a point where the flash got darker. After you say the ISO to 400 you should have seen that the object was better exposed at the same distance where it was too dark before. Also, you should have found that the area behind the object had more light than the ISO 100 or auto setting.
Changing the ISO can be very helpful in many indoor situations. It will save your batteries, give better exposure from a distance, and if you are photographing new born babies there will be less light flashing their eyes.
