A Filter Holder for the Samyang 14mm lens

A while ago I bought a Samyang 14mm f2.8 lens (also available branded as Walimex or Rokinon) to use with my crop sensor DSLR. On a Canon cropped sensor it gives an equivalent focal length of 22.4mm, making it the widest I’ve got. Once I remembered how to deal with manual focusing (with no focus confirm) and the lack of exposure coupling I’ve been very happy with the results it’s produced. The only major problem with the lens is that there’s no easy way to work with filters due to the built-in petal shaped lens hood.

While it’s possible to get round the need for ND grad filters by exposure bracketing and subsequently blending images in processing, it’s not so easy to produce long exposures to capture water and cloud movement. So how do you fit filters to the Samyang 14mm lens? One option is the square filter holder Samyang are now supplying to use with this lens. Unfortunately both the holder and filters look pretty big (not very practical for carrying around) and filter availability appears to be very limited.

Maybe a more practical solution is to build my own, allowing me to use my existing 100mm Lee/Cokin Z compatible square filters. Using these there’s likely to be intrusion into the frame on a full frame camera, but with a crop sensor camera it shouldn’t be an issue. At least that’s the theory …

The design is basically a foam lined tube that’s a push fit on the lens hood, with a butchered 100mm filter holder grafted on to the front.

Materials

  • Cheap Lee compatible 100mm filter holder
  • 110mm diameter black plastic drain pipe
  • 1mm countersunk head bolts (x4)
  • Self-adhesive foam tape: I used 25mm wide, 8mm thick neoprene rubber strip.
  • 2.5mm nuts (x4). The size may be different depending on the design of the filter holder you’re using; and with some replacing the supplied nuts may be unnecessary.
  • Glue (I used Gorilla Glue, but epoxy type glues would probably have worked better: see build description)

Step 1: Cut the pipe

Cut a 30mm length of drain pipe. Depending on what you use to cut it you’ll need to clamp it quite solidly, as you want the ends to be as square as possible. When it’s cut, sand the ends until they are smooth. I used an orbital sander to remove the worst of the cut marks, then finished it by rubbing both ends on a sheet of sandpaper laid on a flat surface. When you’re happy with the finish, give it a wash to remove the dust – it’s nasty stuff that you don’t want getting anywhere near your photography equipment.

Step 2: Paint the pipe

This step is optional, but I’m not too keen on the outside of the adapter being shiny black and looking like a piece of, well … drainpipe. Roughen the surface with fine sandpaper, wash it again then apply a coat of primer and a couple of coats of matt-black paint. Try to keep the paint off the end of the pipe that’s going to get glued to the filter holder. If you do get some on there you can always remove it with sandpaper when the paint is dry.

Make a Filter Adapter for the Samyang 14mm lens

Step 3: Prepare the filter holder

In order to attach the pipe, the back of the filter holder needs to have a flat surface. The preparation required will vary depending on the make/design of the filter holder you’ve chosen. My unbranded one (pictured above) has countersunk screws fitted through the filter guides from the front, with quite large ribbed plastic thumb-turn nuts on the back. The following description details the preparation needed for my filter holder, and will need to be adapted for other designs.

Make a Filter Adapter for the Samyang 14mm lens

Remove the filter guides from the filter holder.  The screws will need to be reversed and countersunk flush with the back of the filter holder so they don’t get in the way of fixing the pipe. For the moment you can use the captive nuts on the front of the filter guides when you reassemble, but they stick out quite a long way, so should probably be replaced with regular nuts in the longer term.

Step 4: Fix the pipe to the filter holder

Since I’m potentially going to be putting some (relatively) expensive sheets of glass in the filter holder I decided not to trust just glue to hold the filter holder in place on the mounting pipe. This makes this step a little more complicated, but is good for my peace of mind.

Place the pipe centrally on the filter holder and draw round it, inside and outside. This will give a pair of concentric circles which can be used as a drilling guide. Mark four (or any number you’re happy with) evenly spaced points half way between the circles and drill out with a 1mm drill. Now glue the pipe in place and allow to set. I used Gorilla glue, which, while giving a very strong bond, does appear to expand quite a bit as it cures. This bubbles out from the joint and leaves an uneven surface round the outside and inside of the join.

You can smooth down the outside a bit with a needle file, but the inside is difficult to reach. I also painted over the glue with black paint to improve the appearance. If I ever make another of these I’ll use two part epoxy to fix the pipe to the filter holder.

I was originally planning to drill and tap holes into the end of the pipe, but tapping a 1mm thread into this plastic is like trying to cut a thread on a piece of soft cheese. Instead I decided to use the 1mm bolts as pins glued into holes in the pipe. Using the holes in the filter holder as guides, drill into the pipe wall to a depth slightly greater than the length of your 1mm bolts. Add a little glue to each hole and push the bolts in, then leave to dry. This should give a secure fixing – if it ever starts to come apart you should get a bit of warning (i.e. a gap appearing between the pipe and the filter holder) before the filter holder falls off!

Step 5: Line the pipe with foam

The difference in diameter between the outside of the Samyang lens hood and the inside of the 110mm pipe is about 15mm, so you need tape that’s just over half that thickness (about 8mm if you can get it) to ensure it’s a tight fit on the lens hood.

I managed to find some 25mm wide by 8mm thick neoprene rubber tape, which is a bit denser than foam tape and is just about perfect. Cut a piece about 33cm long, peel off the backing a section at a time (if you peel all the backing off at once it’s very difficult to get it straight and even). Stick it around the inside of the pipe at the open end, i.e. the end that’s not glued to the filter holder. Trim the excess length off to get the ends to butt together. Sticking the tape at the open end of the pipe should ensure it doesn’t restrict the opening at the filter adapter, as this might cause intrusion into the sides of the image. The finished article looks like this:

Step 6: Attach to your lens and get shooting

Make sure the filter holder is pushed far enough on to the lens so that the top and bottom of the lens hood are in contact with the plate. With the holder on a camera with a crop sensor, there shouldn’t be any intrusion of the filter guides into the sides of the frame. This is what it looks like attached to the lens:

Make a Filter Adapter for the Samyang 14mm lens

And a quick test shot using a ten stop neutral density filter (ND1000), taking the exposure from 1/100 second to 10 seconds:

Make a Filter Adapter for the Samyang 14mm lens

Since building the filter holder I’ve had a chance to try it on a camera with a full frame sensor. Now a 14mm lens gives a seriously wide field of view when there’s no APS-C  1.5x or 1.6x multiplier being applied, and the bad news is that with a full frame sensor there’s a lot of adapter visible in the sides of the frame. Not a problem if you’re going to crop all of your images to only use the central area of your sensor, but that rather negates the reasons for spending all that extra cash on a full frame camera in the first place. So really as it stands this project is only useful for those of us who use crop sensor cameras. Maybe the answer for full frame is to build something similar using a 150mm filter holder. One for the future …

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