Combining an optical design with in-camera corrections that keep distortion under control, this lens offers an extremely well-controlled sagittal coma flare that yields pin-point stars from edge to edge. Additionally, a new Manual Focus Lock (MFL) switch disables the focus ring, ensuring that focus never changes, even after hours of shooting under chilly, dark skies. The lens has also been developed to accept 82mm front filters, a rarity on ultrawide primes, and another unique feature includes a rear filter holder, which accommodates sheet filters for various creative effects.