Fix Vignetting with Cokin Z-Pro Filters

by David Gibbeson

When I first used my Cokin Z-Pro ND filters I was quite happy until I bought a Sigma 10-20mm ultra-wide angle lens. I thought that I was all set, on my path to creating amazing photos. I remember the disappointment of there being a slight vignetting on the photos taken at 10mm, which seemed to be nearly all of the ones from my first outing with the filters. I could easily fix this in Adobe Lightroom so figured that while not ideal, I could cope.

Not long back I decided it was high time I made the change to full frame. I bought a Canon EOS 5D Mark 2 just as it was announced that they were being discontinued. I figured it was a good a time as any and managed to get a good deal as prices started to drop. Obviously there was no way my Sigma 10-20mm was going to work with the full frame body so I had to find a new lens to replace it. I opted for the Canon 17-40mm L as it seemed to be a great replacement.

I can’t begin to tell you how disappointed I was once I started to take a few shots and glancing down to check my histogram noticing severe vignetting on the screen. It was much worse than I had experienced on the 10-20mm.

I checked to make sure everything was properly attached and it was. I found myself debating about what to do as the light was just about approaching its sweet spot. It was then that I looked at the z-Pro filter holder and realised it had 2 slots to stack filters and the screws tat held it together had a thumb grip…

Rushing as quick as I could while trying not to drop the tiny nuts and bolts as there was no way I would find them on the Exmoor grassland at the top of Winsford Hill. After what seemed an age I had reassembled the holder without one section and put it back on to the camera to test. I was chuffed to bits to see the vignetting had totally gone!

I still had time to take a few photos with my new 5D happy in the knowledge that I had a good chance of nailing the exposures now with the aid of my ND filters. The light was excellent so I worked with the 1 tree that I had picked for my compositions and ended up with a few shots that I’m really pleased with.

Here is one of them:

A tree at Winsford Hill on Exmoor at sunset

A tree at Winsford Hill on Exmoor at sunset


Here are some close up photos of the Cokin Z-Pro filter holder to show what bits I mean. I made sure that the thread for the tiny bolts pointed towards the camera body to minimize the vignetting. I’m happy to say that this seems to have fixed the vignetting on the Sigma 10-20mm as well. I still want to get some Lee filters eventually though.

Here is the Cokin Z-Pro filter holder with 2 sections half attached to show where they are. The best way to remove them is to undo 1 bolt at a time and remove the section. This way it makes reassembly much simpler.




Here is a photo showing the bolt from the side. All that is required to undo them is a small straight screw driver and your fingers to hold the thumb grip nut.



Here is the filter holder with the sections removed. Notice how I have made the bolts protrude most towards the camera body. It might be worth sourcing shorter bolts for a tidier job. I have kept mine as they are so that if I need to I can add the sections back in if I want to stack filters.


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