I'm interested in picking up a fisheye lens to do some really wide angle photography, but I want to be able to use ND filters to do some long-exposures as well. The problem is that m43 doesn't offer any super wide or fisheye lenses that will accept threaded circular filters (yes, I'm aware of the Olympus 9-18). I've seen the hack for the 7-14 Panasonic lens where you can make it accept gel filters at the rear, but that's kind of a hassle, and finding optical quality gel filters isn't as easy as buying circular ND filters (which I've already purchased). This got me to thinking, what if you took the lens cap from a Rokinon fisheye lens (do they even give you one? if not, can you purchase one? worst case just buy the one for the Panasonic fisheye), and cut the center out of it. Once the center was cut out, glue/epoxy a step-down ring in the hole of the lens cap, that way you could just screw whatever filter you wanted in to the threaded portion of the step-down ring, and slide the assembly over the built-in lens hood, enabling you to use whatever threaded circular filter you desire with a fisheye lens. Surely I can't be the first person to have thought of this, since it's a pretty simple hack. Has anyone seen something like this mentioned before, or better yet, have any results?
You *do* get a lens cap with the Rokinon, fwiw, but I suspect you'd get some hard vignetting if you tried what you are thinking.
What you are suggesting would vignette a great deal when in place. Due to the near 180 degree angle of view, anything in front of the first lens element will vignette or show up on the edges of the image... You can always crop the image to remove the vignette, but then you might as well just get the 9-18mm. There was a thread some time ago (https://www.mu-43.com/showthread.php?t=59267) detailing how someone machined the built-in hood off a Rokinon to allow filters to be added, but it still resulted in some vignetting. I have the Panasonic gel filter frame from the 8mm fisheye to add to my Rokinon, but still have not settled on a way to attach it yet. Gel filters on the back of the lens does show some promise, but obtaining filter material isn't easy or inexpensive.
There was a thread some time ago (https://www.mu-43.com/showthread.php?t=59267) detailing how someone machined the built-in hood off a Rokinon to allow filters to be added, but it still resulted in some vignetting. That was me. I'm still using this as there is still no 8 or 9mm m43 prime that accepts filters available. I shot 16:9 format and just crop the bottom and sides a bit - the top of the images are normally sky, which is easy to clone in PS.
http://lucroit.com/SHOP/product.php?id_product=21 Lucroit's 165mm filter system, if the Samyang has the same front end of the lens as the canon/Nikon version
