Despite white wall tests of the Canon EF 28mm and 135mm lenses showing acceptable levels of vignetting, my first real world use of them ended in failure.
After spending a few weeks with the Sigma 50mm ƒ/1.4 Art, I've come to realize maybe Sigma lenses aren't the solution for me. At least the 50mm has a very short focus throw, making manual focus a tedious process, even with focus aids like focus peaking and focus zoom. Autofocus is just too unreliable and slow to depend on for all occasions, making manual focus capability a priority.
If you'd like to contribute your findings, please include lens specifics (brand, focal length, maximum aperture, lens version, firmware version, and if it's weather sealed or stabilized), adapter used, and camera used. Full sensor sample shots without the lens hood (JPEG, 2000x1500 pixel minimum) needs to be of a white or gray background at the widest aperture at both minimum and infinity focus, repeating this at ƒ/8 and at minimum aperture, be it ƒ/22 or ƒ/32.
This is the first in a series of posts on individual lenses adapted to the Fujifilm GFX 50S with the TechArt Pro EF-GFX adapter. Fujifilm GFX 50S, firmware v3.30 (latest) TechArt Pro EF-GFX, firmware v1.01 (latest) Sigma 50mm ƒ/1.4 Art, firmware v2.02 (latest) Summary: Full compatibility: Autofocus, EXIF OK. This lens shows a correctable vignette throughout the aperture range but is heavily affected by focus breathing. As the aperture shrinks, focus toward infinity causes the vignette to become harder and more pronounced. Despite this, it is easily cropped and corrected while maintaining 45mp or more.
As I have alluded to in a burst of recent posts, I am planning to generate a small database of lenses for use on the Fujifilm GFX series. Here's my chance for an introduction to give my rationale and to lay the foundation of this endeavor. I'd like to break this down into three "Y's." Let's begin with a personal "why": I'm choosing to use Sigma lenses to obtain focal lengths and apertures not currently offered in the GF lens lineup. Fujifilm's lineup is sparse at best, and apertures wider than ƒ/2 aren't represented. It's not that I'm a bokeh whore; it's that I need more light gathering for astrophotography and Fujifilm's widest lens, a 23mm, has a maximum aperture of ƒ/4 and that's just not going to work without a star tracker due to the sensor's 51MP resolution. I'm hoping to print a few of these so what counts for "sharp" on the web doesn't work at 20" print sizes. Other benefits: 35mm lenses are much cheaper, especially used prices, and these lenses mostly have direct focusing units unlike the "fly by wire" systems used on Fujifilm lenses. The GFX system just isn't mature enough to have grown both a complete lens lineup or a diverse used lens market.