available light, lens flare, and bokeh

I'm not sure what my aversion to the camera flash is (I know it's useful under certain circumstances), but I'm really into taking photos using only available light. Of course, when it's night, available light can be pretty scarce. I went out on Halloween and took two dozen photos, but only two came out the way I wanted them to.

Police Motorcycle Line

There's an annoying green blip in the center of this photo. It's lens flare, but for some reason, sodium vapor streetlights (the yellow-orangish kind) flare as green in the lens. I'm not sure why that is, but I'm still actively researching the subject. If anyone has any insight as to why this happens -- I'd appreciate a good lead or theory.

Classic Bart


One of the prominent effects in low light photography is the shallow depth of field and what some people call bokeh (Japanese for blur). Bokeh isn't well-defined, but people seem to know it when they see it. My definition of bokeh is "background blurring with intentional aesthetic consideration." Background blur is pretty common in portraits to bring attention to the subject of the portrait (as in Classic Bart above), by diffusing the background details away. Bokeh involves using the background, but diffuses it to make it abstract (as in Police Motorcycle Line above). My goal in that photo was to have the streetlights take on a feel of festival/holiday lights by appearing as an abstract string of point lights in the background, as well as provide a depth cue. This is my own definition of what bokeh is though -- I'm sure there will be differing opinions as all of this is pretty subjective. I still don't know what people are talking about when they say the bokeh is "smooth and creamy" though.

This brings me to my camera tip of the day. If anyone out there would like to try their hand at experimenting with depth of field, background blur, and bokeh you can do it day or night by setting you camera's aperture to be larger. Check your camera manual and see if it has an "aperture priority" mode. If so, set the aperture to be as large as possible (smaller f-number = larger aperture). Focus on your subject (particularly the eyes and nose if it's a person or animal), and snap. The result won't be visible until after the picture is taken (i.e. you won't see the blur in your viewfinder). The aperture is set only when the shutter clicks, which is why one does not see the blur in the viewfinder.

A lens with large maximum aperture (f/1.4, f/1.8, f/2.8) really helps in getting these effects. Most consumer lenses on point-and-shoots as well as SLR kits have much smaller apertures (f/4.5, f/5.6) which makes background blur almost impossible. This is why I'm on a mission to get consumers the information they need to get a camera, either point-and-shoot or SLR. That is, to stop making decisions based on megapixel count and image stabilization features, but rather the quality and attributes of the lens. The lens is the limiting factor on what a camera can and can't do, even in full automatic mode.