You get wide and flat imaging field with the Vixen VSD 100mm f/3.8 Astrograph Telescope that covers 645 medium format cameras, and 5 elements in 5 group lens to completely eliminate a violet tint in chromatic aberration (blue halo). This telescope engineered by the product experts at Vixen features an SD lens in the front objective group and an ED lens in the rear objective group to achieve superb color correction. The Vixen VSD 100mm f/3.8 Astrograph Telescope is ideally suited to detect faint stars and the image circle is as large as 70mm in diameter (60% illuminated). The Vixen VSD 100mm f/3.8 Astrograph Telescope w/ SD Apochromatic Obj Lens boasts of a 99.9% light transmission at the maximum per lens surface and achieves superb images with extremely high contrast and no ghost and no flare images. With the Vixen VSD 100mm f/3.8 Astrograph Telescope w/ Aluminum Storage Case, astigmatism and coma aberrations are corrected to an extremely high level of image quality.