I like crisp images, like this one I just took of one of my toys:
You see, here’s my floor, with that toy, using available light:
Nothing wrong with that, but I prefer more crisp sharpness, more contrast. Like the sharpness flash gives you:
I took that picture purely to illustrate how to take this picture, Namely, with a Fujifilm x100 camera (which has an APS-C sensor) with a Pocketwizard on the flash hotshoe and “external flash” enabled. The camera was set to 200 ISO, f/8, 1/125 second: standard studio settings. Two flashes, one on the right at 1/16 power; one on the left at 1/4 power, fitted with a 1/4″ Honlphoto grid:
When you click through to view these at full size, they are good.
View that full size and a few things may occur to you. Like “remove dust with brush and blower before taking any close-up flash shots”. And “a small camera, like the Fujifilm x100, can make excellent, sharp, crisp photos when you use it well”. But especially: “flash is one way to make photos crisp, both in reality and in perception”. Reality, since the flash lasts only 1/1000 sec at full power, and therefore 1/4000 sec at quarter power”; hence, there will be no motion blur. And perception, because exposing to the right (i.e. brightly) and with lots of contrast makes things crisp.
Look at this image full size:
There you have it: sharpness. just one more advantage of using flash.