Typically, a long focal length of 500 mm is housed in a mount that is also 500 mm long. To achieve a handy, universally applicable, and compact solution, this lens employs a clever trick. The light path is simply folded using two high-precision ground mirror rings. This results in a compact design and an aperture that is over 50% larger compared to a lens of the same focal length, along with a very short minimum focusing distance of just 2 meters. Focusing is done manually. The lens can be used with either automatic exposure or manual exposure settings, depending on the camera. Due to the folded light path, it is technically impossible to incorporate an iris diaphragm. If light reduction is necessary, this is easily achieved with neutral density filters that can be screwed onto the rear lens. There is a thread M34x0.5 available for this purpose. Conveniently, the lens does not have a fixed infinity stop. T2 connection, operation tip: The T2 adapter is screwed onto the optics, and then the lens is locked in place. The side screws on the T2 adapter allow for adjustment of the lens position after loosening, aligning the index upwards. Retightening the screws securely holds the optics and adapter in place. Save time in post-processing. Many lens errors such as distortion, edge softness, or vignetting occur in the outer areas of the image. When using a lens designed for full-frame on a camera with an APS-C sensor, these areas are not utilized. This way, you achieve maximum quality, eliminating additional post-processing time for correcting lens errors.