To flash or not to flash, that’s the question - at least for this article. There are two primary issues, which are the Ying and Yang of answering that question - the Technical and the Aesthetic.
At times, there just isn’t enough available light to take a picture without a flash. Other times, the use of flash is not necessary, but can improve a photo greatly.
There are many situations that are borderline flash or no flash. It may be necessary to consider the end use of the picture. If the photo is intended for a computer screen poor light is not that important, because light is projected through the photo.
If the picture will be printed in black and white for a newspaper or if copies will be made on plain paper, flash can be a lifesaver. Newsprint absorbs ink into the paper, which makes pictures darker when printed.
If photographing dark completed people, flash will open up shadows and give modeling and definition to the face. Imagine a shaft of light streaming through a window onto someone’s hair, creating a hallow effect. Even though the face isn’t that distinguishable, using flash will destroy the mode. Sometimes, aesthetic rules over a technically correct version.
Another aesthetic reason not to use a flash…once a flash is fired, people are aware pictures are being made. Their expressions may change from natural to posed. The photographer may get one shot that’s natural, but rarely additional.
If natural light photos of people are pleasingly expressive, the natural expression may be more desirable over a well-lit posed image. However, if one can’t see the expressions in their faces due to poor print quality, a flash image may be a better solution.
Not sure what the usage might be? Want to be able to use the photo in a number of ways? One needs to be sure the quality will work anywhere it may appear.
If shooting in available light one may need to use a high ISO (800 or 1600), but the drawback may be pixilated images. If the photo will be printed large for use in a display booth or a slick magazine, then one needs to shoot at a lower ISO and use flash.
There may be occasions when flash is not permitted. Museums often don’t allow flash since it can fade the colors in prints or fabrics.
Surprisingly, people don’t use flash outside when it would help open up shadows. But they use it inside where it can destroy mood and inhibit a more natural setting.
Digital image results can be seen immediately. Why not shoot these tricky lighting situations both ways, then chose the better image?