I'm looking for a zoom lens for my GH4 with the following characteristics so I can mount it on my Century Optics 1.33: ParfocalFront assembly does not rotate (needs to hold the adapter level)As fast as possible (maybe in combo with speed booster)Covering the focal length the adapter will allowAs affordable as possibleThis would be for narrative filmmaking. I'm wondering there are any older/vintage zooms that might might fit the bill. They don't have to be perfect, but workable enough for me to get the practice & feel to see if I find it engaging enough to spend for some high quality glass down the road. I know there are Vivitar f/2.8's that are parfocal, but I don't know which (if any) have a front assembly that remains stationary while zooming/focusing. I also don't know what maximum focal length the DS-1609 adapter will allow. I found several topics in these forums which mention parfocal options, but 1) most are roughly $600+ which is out of my price range, and 2) even if I can save enough $ for one of those, it is not clear if any of them have a front assembly which remains stationary during zooming. Maybe there is no solution that will fit my budget, but I'm hoping there are some experienced Century+Zoom owners out there that can help. Thanks!