Upload & Sell: Off
| p.1 #1 · p.1 #1 · Modifying the Cokin Z filter holder for WA lenses |
How to minimize potential wide angle vignetting on a Cokin Z holder
For those of us owning a lens with an 82mm front thread, finding a flexible filter arrangement has been some struggle. Round 82mm CP are available, but >2 ND require special order and for GND either a very steady hand hold or a filter holder are used. Based upon discussion of the “wide” lens adapter for the Lee filter holder, I did a little “rebuilding” of the Cokin Z Pro filter holder, since I already owned one. The original design has one slot on the rear for the lens adapter, and 3 on the front for 4 inch (100mm) wide filters. It occurred to me that possibly the lens adapter could go on the front of the filter holder, not on the rear. This would effectively bring the filters closer to the lens, reducing the total depth of the adapter and minimizing the potential for vignetting.
Here is a picture of the modified filter holder with the adapter on the front of the holder. The lettering on the adapter “Cokin 0.02 th 0.75 France” is normally against the back of the holder and not visible. I have removed a spacer and slot on the rear of the body and a spacer in the holder front, so that there are now 2 slots in front in addition to the one needed for the adapter.
This orientation of the lens adapter places the adapter threads within the central hole of the holder. The next picture of the rear of the holder shows that for this 82mm lens adapter there is about 6mm between the hole in the holder body and the adapter threads. My 82mm lenses need 2-3mm of space for the lens threads and hood mount, so there is lots of clearance. The 86mm lens adapter clearance will be much closer, depending upon the depth of your lens hood bracket.
The adapter is held in the slot with the 3 plastic pins on the top/bottom of the holder; this does not change for front or back mounting although the top one does not fully slide out of the way for front mounting. Here is a picture of mounting the lens adapter, as one set of slots have to be opened to clear the adapter threads from the holder body. Frequent changing of lens adapter sizes in the field would be a pain as one could easily loose the small knurled nut. However I use a step up 77-82mm step up ring for my 77mm thread lenses and only have this one lens adapter for the Cokin Z. The parts on top are all of those removed from the original holder.
All that you need is some shorter metric thread screws, as we have reduced the depth of the holder assembly. I got the shorter screws, shown in the center of the above image, at Orchards Supply Hardware store. The slots easily provide safe separation of the filters from the lens adapter. Here is the filter holder modified for wide angle lenses mounted on a Zeiss Distagon 21 f2.8 ZE.
While vignetting on the 82mm front thread Zeiss 21 and Canon 24 TSE II have not been a significant issue, vignetting of this filter holder on a Canon 16-35 f2.8 II at the wider focal lengths has been reported as a problem. Overall this modification has reduced the distance from the lens element to the gel filters by 6 mm, minimizing any potential for vignetting. I don’t have a 16-35 II to test this out. Anyone?
This WA modification has reduced the overall depth of the filter holder assembly plus mounted lens adapter by 14mm, making it much easier to store the assembly in my photo bag.