Photography 101: Flash Tips

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The easiest way to have sufficient light for your picture is using flash. Flash is there to give more light so that your film or sensor can record what is in front of your lens. Usually the flash you have is the one built in your camera or the one that you attach on your camera’s hotshoe. However using flash is also considered as the easiest way to ruin your picture. Deer on the headlight, slightly over exposed subject with dark background, is the most common result of using the flash indoor when ambient lighting is too dark.

This article is to explain a little bit principle about using flash to beginner photographer (that includes me !). Those principles are, especially in a quite dim ambient lighting :

1) Aperture dictates how much the light from flash will get into your film or sensor.
The larger the diaphragm opening (the smaller the aperture number) the more the light getting through to your film or sensor. And vise versa.

2) Speed dictates how much the light from ambient will get into your film or sensor.
The slower the speed the more the light from ambient that gets through the film or sensor and vise versa.

Example:

Let’s say you are in a relatively dark ambient lighting: outside in a city street during the night (where light is present from the street and other lamps but quite dim) and you want to take a picture of your friend standing somewhere there. Using your flash set in manual just for an experiment. In this scenario your friend will be lit entirely by flash (presumably he is in flash reach) therefore the exposure of your friend face and body will depend on the light coming from the flash. Meanwhile his (or her) background exposure will depend on the ambient lighting. you can see the result on your LCD for each result by varying different aperture and speed.

With the exception of studio photography that we all know that flash is used almost all the time (only sometimes they use window light), good photo should always look natural, therefore the presence of artificial light should be hard to detect at least by untrained eye. And this means that wherever there is already a main light (e.g. sun, lamps, etc.) we should only use flash as a supplement of whatever main light in that very location and timing. One example is filling the shadow in a bright sunny day, however not to “over fill” it so that the picture looks boringly flat. Lighten the shadow moderately to create an effect of still having the shadow but the detail in the shadow is preserved. Now that sounds difficult, but with digital nowadays you can always experiment and having the result instantly.

The more difficult than shadow fill during sunny day is to deal with room lighting that is not bright enough to guarantee enough speed to secure the subject from movement blur. The idea is to balance a room lighting with our flash, again, not to overtake the room lighting that creates a flat and overexposed subject that does not blend in with the actual atmosphere. It is difficult because mainly room lighting has different color than our flash. Most of the time you have either incandescent lamp or fluorescent lamp which both case does not match with your flash light color. In photographic terms it is called color temperature. One way of matching the color temperature of your flash with the lamp is to have a color correction filter attached to your flash. That way your flash light will not be like one that comes from nowhere.

I myself find it very difficult to match ambient lighting with the flash. Especially when you do not have the correct filter with you. The situation usually leads to not to use the flash at all and pump up the ISO setting to gain more speed. One other compromise option is to use ‘slow’ mode in your flash where you can use your a bit of flash to adequately lighten up the subject just to secure the reasonable exposure — and hopefully freeze the movement — and drag the speed to still allow the ambient lighting to be recorded properly. You need to experiment the speed to create the preferred effect in your film or sensor. You might want to use tripod as well however handheld will usually deliver background lighting effect that you might also like.

However, I always love what the natures provides. Probably that would answer why my flash is sitting for the last four months. 

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2 Responses to Photography 101: Flash Tips

  1. steve moskowitz says:

    Perhaps you can help me resolve the issue that i am having. I am trying to use room lights in addition to my on camera flash to increase the ambient room light. The problem is that when I turn on my 580ex the total light output is much less then when i just fire my room lights or visa versa .In other words my on camera flash for some reason diminishes my off camera flashes. I tried switching the master slave switch on the 580 as well as the excalibur heads that I am using(it only has a master slave switch). it did improved a bit but it is sill at least one bar less on the histogram than without the 580. I’m sure its a simple thing but I just cant figure it out. can you help?
    Thank You

  2. looselens says:

    Hi Steve,

    Many thanks for visiting.

    If I can understand correctly, your picture becomes darker when you use BOTH on and off camera flash.

    I am not familiar with Canon flash system (since you mentioned 580EX).
    In my Nikon system, usually that can happen when you use on-camera flash with TTL capability, combined with non TTL off-camera flash using optical trigerring system. TTL flash usually emits a few low power flash before the actual flash itself. This low power flashes (let’s call it pre-flash), are fired to evaluate metering. This pre-flash is strong enough to fire the off-camera flash.

    Therefore when the actual on-camera flash fires and recorded in the film (or sensor), the off-camera flash does not fire, since it already fired before by the pre-flash and had no sufficient time to recharge the capacitor to re-fire.

    Therefore you may want to try to NOT use the TTL flash :

    Set both flashes power to manual
    Set your camera in manual

    If you use digital camera, just play with the flashes power output. Set your camera to a certain combination of speed and aperture, e.g. 1/60 and f5.6.
    Assuming you shoot a subject with a background, where your on-camera flash illuminates the subject (e.g. a person) and your off-camera illuminate the background, adjust manually your on-camera flash to adequately illuminate your subject and the off-camera flash for the background. And adjusting off-camera flash can also mean moving closer to or farther from the background to fine tune the illumination level.

    If you use film instead of digital camera, you will need a flashmeter:

    Set your camera to a speed e.g. 1/60.

    Set your on-camera flash power output and measure your subject using the flashmeter. For example, you get f5.6.

    Set your camera aperture to follow what you get with your measurement: f5.6.

    Set your off-camera flash power output and measure the background.
    If you get f5.6, your background illumination level will be the same as your subject.
    If you get f8, f11 etc (smaller aperture), means you will have brighter background.
    If you get f4, f2.8 etc (larger aperture), means you will have darker background.

    I hope I answered your question and gave you some idea on some experiment to resolve the issue.

    Cheers,

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