Something all photographers worry about, this the third in a series of posts will look at:
The aperture you use can have a major impact on sharpness. The effect can be pleasing or unwanted.
Generally most lens will be a little unsharp wide open, for a fast portrait lens a little unsharpness round the edges can be quite pleasing. The main difference between ‘professional’ lens and ‘consumer’ lens is generally, they are faster and a little sharper wide open, but you can still get great results with cheaper lens. The key is to use them at there optimum aperture. Most lens even the cheapest can perform quite well when stopped down a little.
If your after a simple rule use your lens at f/8 or f/11 and you will get the best out of it.
There is also another consideration. Defraction. Closing down the lens a little does improve sharpness but closing down too far actually starts to lower quality as defraction starts to impact. So as a general rule close down a stop or two for maximum quality and sharpness but don’t stop down too much and only shoot wide open open if you want a slight softness.