![]() We then re-attempted the test in live view and got perfectly-sharp images every time. We were able to get a few sharp images of closer subjects, albeit never consistently. At various focal lengths, both lenses failed to focus accurately even after multiple attempts. To simulate a real-world shooting scenario, we started out with an informal test to see if either copy of the lens (henceforth referred to as copy A and copy B) could focus on a car parked some 20 meters from the lens. We checked for firmware updates using the Sigma USB dock and were informed that firmware v1.00, the version installed on the 18-35mm from the factory, was the latest firmware. Initial tests were repeated with a second K-3 body as well as a K-50 to verify the results. Cameras & Settingsįor the tests to follow, we used a Pentax K-3 with center-point AF.S PDAF in focus priority mode. Because the 18-35mm has a relatively low degree of magnification, AF inaccuracies can usually not be discerned through the viewfinder, and this can easily catch you off-guard. In practice, this meant that many photos shot in everyday scenarios ended up being blurry despite receiving AF confirmation from the camera. Our original findings suggested that the 18-35mm suffered from front- and back-focus so inconsistent that it could not be reliably corrected via the Sigma USB dock. The degree of inaccuracy can be so great that frequently leads to unusable photos in practice. While shooting through the viewfinder, the 18-35mm can often fail to focus accurately on subjects that should normally not pose an issue for a modern camera system. Thus, in an attempt to arrive at a more conclusive verdict regarding the 18-35mm's autofocus, our forum administrators decided to test two additional copies of the lens side-by-side. ![]() However, while many user reports agreed with our findings, other users stated that they haven't experienced any autofocus issues whatsoever. We therefore suspected a problem with how the lens interacts with the camera during phase detect autofocus (PDAF), as no issues were observed in the live view contrast detect autofocus (CDAF). ![]() These initial findings were verified using five copies of the lens, at different times, across three different K-3 bodies among others. Unfortunately, in our in-depth review of the 18-35mm, our staff reviewer Heie discovered that the lens suffered from serious autofocus issues while shooting through the viewfinder. Not only is it the world's first DSLR lens with a fixed aperture of F1.8, but it has also proved to be an optical masterpiece with image quality and bokeh comparable to that of high-end prime lenses. The Sigma 18-35mm F1.8 "Art" is an impressive lens. Nature One very nice looking Camellia.Still Life Very pretty Christmas Scene.Still Life Obligatory ornament and light shot.Weekly Challenge Winner - Weekly Challenge #635 Four or More.Project 52 PROJECT 52-11-67- NECESSARY THINGS-Recreation.Weekly Challenge Weekly Photo Challenge 636: Planes, Trains, and Automobiles.Weekly Challenge Best of PF Newsletter Challenge #9: Santa's on his way!!.Weekly Challenge Caption Contest - closes Midnight EST 12/27/23.Monster Adapter LA-KE1 Pentax K to Sony E Lens Adapter.Pentax O-ICK1 Sensor Cleaning Kit Review.Announcing Our December, 2023 Photo Contest.Astrotracer Type 3 added for Pentax K-1 and K-1 II.Making Fall Colors Pop with the "Gold" Custom Image Mode.November "Towers and Spires" Contest Finalists Announced.
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