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5.1 Using Flash

A flash is often looked at as the light source the camera uses when it is dark, and that is correct. What is often overlooked, is that a flash can, and should, do much more for your pictures.

Even the largest professional flash can not light up an entire stadium, so there is always a limit. I find in total darkness, after a few meters, built in flashes often leave a very noisy, and still way too dark of a picture as a result. So flashes are never really a good substitute for enough light. In a sense they just add light to a photo, but it is always best when the flash is not the only source of light. It does let you see some things but properly used a flash can do so much more.

One of the most important things it can do is eliminate or at least reduce the shadows in a photo. An easy example to understand is if you think of a photo with a picture of a person with their back to the bright sun. This causes the top or side of their head to be brightly lit. Without a fill flash, you can expect a very dark shadow on the subjects face, which is probably what you are trying to photograph in the first place.

By setting your flash to always be ON (Often there is a setting for ON, Auto, and OFF in the menu somewhere) even on the brightest day, it will will soften your shadows and can greatly improve your results. Try it sometime. Not all cameras calculate exposure the same way, so it may not even work for you, but many will be very happy with the results.

For a good explanation of flashes, you can read these.

One of the best flash information web sites available anywhere is Strobist run by David Hobby. Absolutely essential reading. Strobist
Also read the flick discussion group for Stobists on flickr here: »www.flickr.com/groups/strobist/

A flash guru with experience and knowledge who provides free step by step advice on using flash is Chuck Gardner. His web site is an important place if you have the need to learn flash photography. His site is here: »super.nova.org/DPR/

This is specifically for the EOS cameras from canon, but everyone will get information they can use, often the author points out the differences, otherwise your manual will help to explain how your camera does the same or similar things.
»photonotes.org/articles/eos-flas ··· s-flash/

New York Institute of Photography has a tip sheet that has some good info:
»www.nyip.com/digital/dig-tips.ht ··· ips.html


by HRM See Profile edited by Edit This See Profile
last modified: 2008-03-29 11:05:22

This website is a helpful resource to those looking for tips on studio lighting. No longer is it a black magic!


by Gemologist See Profile edited by DavisPhotog See Profile
last modified: 2005-07-21 13:24:20

Flash is a very wonderful and often times mystical thing. For something as simple as it is (a device that emits a blast of light), there are a lot of subtle nuances. There are three key components of using flash:

1) Synch speed
2) Aperture value
3) Shutter speed (one of the smaller components)

Synch speed is the fastest shutter speed at which your camera can use a flash. For some cameras it's 1/250sec, for others it's 1/60th. The most common shutter speed for flash is 1/60th as that's the slowest speed one can generally handhold a camera without noticible blur in photographs. Synch speed for your particular camera may vary, so for that you'd have to look it up in the manual. So, what does synch speed do? If your camera has a mechanical shutter that's a focal plane traverse shutter (leaf shutters on medium format (MF) cameras don't really have a synch speed, but they may have differenct "synch" settings, and on MF cameras it is usually called X synch). What happens is the shutter opens, then the rear curtain closes. If the rear curtain closes too fast, you'll have a nice,perfectly black area on your photo. Most modern cameras won't let you exceed the synch speed and older cameras have the synch speed marked in red on the shutter speed dial. Higher synch speeds (1/200th or higher) are usually only found on higher end cameras, namely dSLRs. Some of the nicer dSLRs have up to 1/500sec synch speeds. This is useul if you're trying to catch action with a strobe and need a fast shutter speed (and a flash).

Aperture controls how much light reaches the film or the digital sensor. For flash exposure, aperture is the primary exposure control. Close the aperture (larger f/ number) for less flash exposure, open it (smaller f/ number) for more flash exposure. Changing the shutter speed in the range of its maximum synch speed and about 1/50sec won't do anything to your exposure when using a flash. This is beacuse your flash will always fire within that shutter speed. See below for more.

Flash really doesn't care about shutter speed apart from the synch speed, however, you can shoot slower than the synch speed without problem. Why would you want to do that? If you wanted to balance flash light with ambient light, for example. You slow down the shutter speed until you get a good mix of flash with ambient, and by doing so you will have a more natural looking flash exposure. Another shutter aspect is something called "high speed synch". Not all cameras have this feature and what it does is it allows you to use shutter speeds faster than the synch speed. The flash fires a rapid series of bursts rather than just one for the length of the shutter opening. High speed synch provides a wider degree of flexibility with your flash.

What is flash exposure compensation (FEC)?
Flash compensation is simply the adjustment of the intensity of the flash burst. Flash compensation is used when your flash is putting out too little or too much light. Many sub-dSLR cameras do not offer this option. Say you are shooting a group of people in black suits. Your flash fires and it turns out that your photograph is too dark. You didn't get enough light coming from the flash. You can dial the FEC (usually located on a flash unit if external, and sometimes controllable from on the body of the camera, depending on the model) up from the "0" setting, usually up to 2 or 3 stops higher (or lower) than the "0" value.

While it may seem counter intuitive, if you decrease the flash compensation the effective range of the flash increases and if you increase flash compensation the effective range decreases. Why? Let's say your flash has a range of 100', if you increase the flash compensation, 100' would still be exposed correctly, but you requested the flash to overexpose, so the usable range is reduced to the longest distance one can get the correct "over" exposure. Conversely, if you reduce the flash compensation that same 100' distance be easily underexposed and thus the range for the correct "under" exposure is extended. Obviously, aperture size affects the flash range, regardless of the level of flash compensation being used.

Written by B52GUNR See Profile. Parts added and changes made by DavisPhotog See Profile.



Feedback received on this FAQ entry:
  • Thanks!! this solves my problem. I was trying to change the shutter speed to get different output but it didn't helped me. Aperture settings works gives the desired output. thanks again!!

    2013-08-16 08:51:00



by DavisPhotog See Profile
last modified: 2006-05-08 11:52:20