The MC4 features a 4-element 4-group design with multi-coated lens elements and fully automatic diaphragm coupling. With the Kenko TelePlus MC4 DGX your prime lens' depth of field is reduced by 1/1.4 but retains the prime minimum focusing distance. TelePlus converters have genuine Gated Array IC. This means that not only the converter's own unique data but all data sent from the camera body provides full exposure metering and linkage for electronic flash photography.