Aperture f/4 vs f/2 vs f1.4
I use my EF 35mm f/1.4L USM to take three shots with different aperture: f/4, f/2, and f/1.4. As you can see, f/4 and f/2 have big difference (in case of bokeh); f/2 and f/1.4 I can see the difference but it’s not too much. When you want to take portrait photo use EF 35mm f/1.4L USM be careful using wide aperture; for example you use aperture 1.4 with far distance with object – the object maybe blur because the focus area is too small. For myself, I seldom to use f/1.4 to take portrait photo because it’s not easy to hit the focus perfectly and you need to set your position in certain distance – otherwise you don’t get the focus area perfectly (because the focus area is too small). Aperture 4 is very safe aperture but remember that bokeh isn’t very good and also shutter speed maybe become slow and you need too increase ISO (in low light condition) otherwise you only get the motion blur. I use f/4 if only I want to take group photo, so I can cover big area. I often to use f/2 to take portrait photo because I still get fast shutter speed and good bokeh (not superb if you compare with f/1.4) – and the most important is you get the larger focus area and better sharpness (compare with f/1.4 because in wide open aperture sharpness usually isn’t very good). Sometimes I also use f/2.8; it’s also nice aperture – but when I use EF 35mm f/1.4L USM, I think f/2 is the optimal aperture compare with f/2.8.