I am deciding on getting an ultra-wide lens mostly because a lot of my shots are taken at 17mm and it's often not wide enough.
I narrowed it down to either the Sigma 10-20mm or Sigma 8-16mm. (APS-C) The problem is that out of the 2 I would prefer the 8-16mm lens except that it has a rounded front element so filters cannot be used and I really like using ND Filters. There are some expensive contraptions that can be used such as the Lee holder with square filters but it my still require taping to prevent light-leaking. (I've read a few things suggesting having to use tape)
The Sigma 8-16 ships with a cylinder like cap onto which the lens cap can be mounted and it also has a 72mm thread for filters. However, according to several articles the vignetting is really bad when filters are used with this cylinder adapter. Some say that at widest angles the cylinder is visible in the photo so cropping is necessary thus rendering the wide end useless. However, I haven't seen any actual photos of this.
Does anyone know of sample photos using this lens with ND filters attached to the cylinder?
Budget is a consideration, the 10-20mm lens can be had for $479 and I can use my existing 77mm filters. Lee holder + square filters (or equivalent) for the 8-16mm can easily be another several hundred dollars on top of the $699 for this lens. The usability of my existing filters might be a deal-breaker here. (As much as I would love to have the extra 2mm on the wide end.)