The 24mm focal length is usually considered the widest you can go without "overdoing" the wide-angle effect in the image. In other words, it's still fairly easy to keep things straight. The Pentax SMC-T 24mm f/3.5 screw mount lens is a compact and reasonably priced 24mm lens, offering very high image quality. This lens is an excellent choice for interiors and scenary. This is an excellent all-around wide angle lens, compact and at a great price.