D610, D750, D850, D5, D3X and the Df with full-frame sensors. Leica produces the S2, a medium format DSLR. Pentax currently offers APS-C, full-frame and medium format DSLRs. The APS-C cameras include the K-3 II, Pentax KP and K-S2. The K-1 Mark II, announced in 2018 as successor to the Pentax K-1, is the current full-frame model. The APS-C and full-frame models have extensive backward compatibility with Pentax and third party film era lenses from about 1975, those that use the Pentax K mount. The Pentax 645Z medium format DSLR is also back-compatible with Pentax 645 system lenses from the film era. Sigma produces DSLRs using the Foveon X3 sensor, rather than the conventional Bayer sensor. This is claimed to give higher colour resolution, although headline pixel counts are lower than conventional Bayer-sensor cameras. It currently offers the entry-level SD15 and the professional SD1. Sigma is the only DSLR manufacturer that sells lenses for other brands' lens mounts. Sony has modified the DSLR formula in favor of single-lens translucent (SLT) cameras, which are still technically DSLRs, but feature a fixed mirror that allows most light through to the sensor while reflecting some light to the autofocus sensor. Sony's SLTs feature full-time phase detection autofocus during video recording as well as the continuous shooting of up to 12 frame/s. The α series, whether traditional SLRs or SLTs, offers in-body sensor-shift image stabilization and retains the Minolta AF lens mount. , the lineup included the Alpha 68, the semipro Alpha 77 II, and the professional full-frame Alpha 99 II. The translucent (transmissive) fixed mirror allows 70 percent of the light to pass through onto the imaging sensor, meaning a 1/3rd stop-loss light, but the rest of this light is continuously reflected onto the camera's phase-detection AF sensor for fast autofocus for both the viewfinder and live view on the rear screen, even during the video and continuous shooting. The reduced number of moving parts also makes for faster shooting speeds for its class. This arrangement means that the SLT cameras use an electronic viewfinder as opposed to an optical viewfinder, which some consider a disadvantage, but does have the advantage of a live preview of the shot with current settings, anything displayed on the rear screen is displayed on the viewfinder, and handles bright situations well. Comparison with other digital cameras The reflex design scheme is the primary difference between a DSLR