I've tried quite a few anamorphic adapters but my biggest problems with adapters was having to double adjust focus on both lenses, image alignment, finding a practical way to follow focus, and/or general fast workflow. I'm a run-and-gun shooter, so ideally, you shouldn't have to do a lot of work to get the shot you need and move to the next spot.
GREAT JOY, a startup has done outstanding work in resolving these issues. It is by far, THE BEST, anamorphic adapter in its price range and totally worth the [as of 2022] $600, because it makes anamorphic easy from the curious hobbyist to seasoned professional.
—1st GJ solution: Double focusing - no more of that! On your taking lens, just focus it to infinity and attach the adapter, and now all focus control comes from adapter.
—2nd: Image Alignment - there are three screws to properly align the image and secure it so it doesn't distort the image when follow focusing, which bring me to...
—3rd: Follow Focus - there are built-in gears on it so you can attach a follow and be up and running fast!
—4th: Process - it's save so much time to use this adapter versus other ones, where you have to play this ballet of aligning, focusing and shifting, which takes time.
Other positives:
-The build quality is excellent. It's all metal and durable. I can see this lasting in my gear room for years.
-The taking lens (back) is 67mm, a popular size.
-The front thread is 77mm, another popular size.
-You can stack it with other anamorphic lenses like Sirui (50mm) for 2x Anamorphic.
-There's a handy guide on the side of the adapter for anamorphic, spherical, etc.
Not necessarily negatives, but things to consider...
-Heavy. >2lbs -- therefore, it will make your rig front heavy so putting it on a gimbal, you'll likely need to do some rebalancing, reduction, and use a vest
-Vignetting; you can't really get a usable image wider than 35mm (on FF) but rarely would I shoot that wide in anamorphic so not that big a deal; you could probably add a focal widener by Opteka on here
-NOT a bokeh beast. Its min. fastest aperture is 2.8, so if you're taking lens is faster, go for it, but bear in mind, the image looks a bit funky faster than 2.8. But it's anamorphic! If sharpness is what you want, don't shoot anamorphic.