The reflecting and diffusing screen is perhaps the cheapest item of all accessories available. And yet this simple tool may do all the difference. Especially if you like shooting portraits.
The screens often comes as 4 in one ore 5 in one, with a diffusing white screen with different slipcovers with sides in silver, gold, white and black. There are mainly three shapes, triangular, round and oval, and of course they come in different sizes.
What you should choose depends on how you need to use them. If you want to keep it in your camera bag it should be small enough to fit in it when folded.
I usually prefer a rather big, round reflector, but there are triangular ones with handles, that are very small when folded and fits nicely in the camera bag.
Using reflectors is no exact science. You can angle it in all directions and use it from different distances. Use silver reflector for stronger effect, white for softer, more natural fill-ins and gold for warmer light. And the diffusing translucent screen is very useful for sunny days. Position it between the sun and the motive.
It is often preferred to position the reflector slightly from below, to fill in the shadows in eyes and under the chin.
In direct sunlight it is easy to bedazzle the model, especially with the silver or gold reflector. It’s also a sign of you overdoing it. Normally you want to enlighten the shadows, not remove them. Try using the screen from a longer distance or another angle.