Aperture 1.4 vs 4
These photos are taken when I went to Sanctuary of Our Lady of Wu Fong Ci, 宜蘭(Yi Lan), Taiwan. When I had a free time, I took some photos to show the difference between aperture 1.4 and 4; I used EF 35mm f/1.4L USM attached with EOS kiss digital X. As you can see from the photos, aperture 1.4 produces superb bokeh compare with aperture 4. In those pictures, use aperture 1.4 you can get shutter speed about 1/3200s but you use aperture 4 you only get 1/250s for same ISO and exposure. Of course 1/250s is enough, but in low light condition maybe you only get shutter speed about 1/10s or 1/20s. One thing to care is when you use 1.4, you must hit the focus exactly, it’s often to miss focus. Bokeh is important but if you couldn’t hit the focus perfectly, you would mess it.