Four external flashes produced by Nikon are compatible with the D40.
Four external flashes made by Nikon are compatible with the Nikon D40: the SB-400, SB-600, SB-800, and SB-900. The SB-800 is no longer manufactured and was replaced with the SB-900.
SB-400
The SB-400 is the most compact option, weighing about 180 grams and typically sold for about $130. It runs on two AA batteries and has excellent battery life. The SB-400 allows the user to "bounce" the flash by flipping the bulb, so that the flash points upward and saturates the entire room with light, rather than just the subject. Illuminating only the subject with a flash results in dark backgrounds and washed-out faces.
SB-600
The SB-600 is much bigger than the SB-400, weighing in at 390 grams, and sells for about $220. It runs on four AA batteries. The SB-600 can be twisted and tilted in any direction (the SB-400 only flips up vertically) and can be triggered by a remote. The SB-600 also has a wider range of exposure compensation settings than the D40's built-in flash does. The SB-600 is a higher-powered flash than the SB-400, but unless you are planning on shooting with flash constantly for an entire day, this won't make much of a difference to your battery life.
SB-800
The SB-800 weighs more than both the SB-400 or SB-600, about 440 grams. This flash was replaced with the SB-900 in 2008 and is no longer manufactured by Nikon. As of October 2010, this flash was available from online auction sites for around $300. The flash includes colored filters to match the light where you are shooting. It also allows the photographer to trigger other external flashes not attached to the camera.
SB-900
The SB-900 is Nikon's most advanced flash, weighing about 530 grams and costing almost $500. Professional photographer and blogger Ken Rockwell writes that the SB-900 "is more of a video game than a flash" and really only suited for professional news or wedding photographers. The SB-900 has a large zoom range and allows for a bit more pivoting than the SB-600 and SB-800. It also offers the remote flash option like the SB-800. For general photographers, the controls on this flash might be overwhelming and hard to use.
Tags: about grams, external flashes, about runs, battery life, compatible with, Four external
