How to Select and Choose Shutter Speed on a Digital Camera

Until now we have only talked about the diaphragm to regulate the exposure with flash, because the aperture affects the intensity with which the beam of light reaches the film. Since flash is instant, the shutter speed DOESN'T affect the exposure level of that light source. Nonetheless, the most frequent is that when making a photo with flash there are other continual light sources, who's greater or smaller registration on film does depend on the speed we choose.

Let's image, for example, we are going to use flash in daylight to illuminate the first plane of a scene which is in a shadow, backlight with a very bright background. In this case, first we would make a measurement of the brightness of the background which we want to correctly expose, and then we will search in the exposure value for a combination which includes the aperture we consider ideal for the flash. This technique is know as filling in shadows , and let's us reduce the contrast of a scene when it exceeds the exposure latitude of the film. Nonetheless, there may be a case when it isn't possible to balance the two lights. If the flash needs a large aperture and the background is very bright, the necessary shutter speed of a camera with a curtain shutter may be incompatible with the synchronization.

In poorly lit interior and exteriors at night, a flash is the main light source, but the registration of other present lights (interior or public lighting, fire) can give many details of the real setting, an also serve as a filling light of the hard shadows caused by a direct flash. Fire, for example, with a potent flash and a fast shutter speed, isn't registered on film, and, in these conditions, a fire is photographed as a pile of ashes. The available light can be used in favor of setting with a timely selection of the

aperture we are going to work with and the shutter speed we select. The greater the difference between the intensity of the flash and the environmental light, the harder it will be to register. Reducing the difference, we reduce the predisposal of the flash, obtaining an equally correct exposure with environmental light details. The shutter speed we need will depend on the aperture we select to expose the light of the flash. The greater the aperture, the more comfortably we will be able to register environmental light without the use of a tripod. Nonetheless, the risk of moved pictures with speeds lower than 60 is compensated by the effect of stopping movement of flash illuminated objects. Therefore, is it is necessary, you can shoot with the camera in hand at much slower speeds without the photograph turning out too moved in total.

Bounced Flash

The “lighting” that a direct flash provides isn't because of the devise itself, but of the quality and direction of the flash of hard light from a point very close to the camera. It is a hard and flat illumination, which produces hard shadows and unwanted shine, red eyes , etc. It is evident that there are better ways to illuminate. Therefore, some flash apparatus are equipped with a reflector (or parabola ) which can be pointed. The beam of light, therefore, can be directed towards a white surface, such as walls or the ceiling, and this way the illumination of the scene will radically change the quality and direction of the light. This requires a flash of greater intensity than if it is direct. Therefore, flashes with a reflector usually have a high guide number and almost always offer automatic operation. Since the only thing that changes direction is the reflector, the flash cell still measures the light reflected from the scene; therefore, the intensity of the flash will always be the necessary one to illuminate the scene in any situation that is compatible with the maximum strength of the devise.