I tend to shoot any lens wide open – at its widest available aperture – whenever I can. When I can’t because it’s too sunny, I’ll sometimes use a neutral density filter to cut the light down so I can. Most lenses aren’t at their best when used wide open, but I tend to like the bit of character the widest aperture brings. My Canon FL 58mm f/1.2, for example, makes shots quite soft and makes any bright parts really glow. It’s imperfect, but that can make for more interesting photos.
When I finally managed to get a lens I’d wanted for a long time, the Voigtlander Nokton Classic 40mm f/1.4, I assumed I’d do the same – always use it at f/1.4. I don’t. With this lens, I fairly often tend to shoot at f/4 or narrower, sometimes using f/8 and even f/11 if it’s bright. When I want a shallow depth of field (which is still quite often), I’ll usually stop it down to f/1.7, half a stop down from f/1.4. I’m not completely sure why, but my theory is that what I think I want out of most lenses is wrong.
I do want a very shallow depth of field. A shallow as possible, really. But not really at the expense of too much sharpness. I really want it sharp where it should be sharp, and blurry as quickly as possible in front and behind. The problem is, that’s expensive. Too expensive for me. So I’ve been settling for the shallow depth of field, with less sharpness and more character, even in the bits that should be sharp. I’ve been compromising, then convincing myself I like it.
The Canon lens can get nice and sharp, but it needs stopping down a lot. Enough to not really have a shallow depth of field any more. The Voigtlander gets quite sharp at f/1.7, so I tend to stop it down to there when I want really shallow depth of field – the boost I get when leaving it wide open isn’t enough to be worth it.
Note: I wrote this quite a while ago, and I use the Voigtlander wide open more often now, but still often close it down a little for a more ‘normal’ look. I still love some lens character in images, but perhaps not as much as I thought I did.