Modifying Rokinon 8mm lens for a Canon 5D full frame sensor

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Modified Rokinon 8mm Fisheye LensI’ve read a lot of posts and threads about modifying a Rokinon 8mm T/3.8  lens with attached lens hood to produce a circular fisheye on a full frame camera but coming across good advice is tough.  Based on the few bits of information I could gather I decided to take a crack at modifying a second-hand Rokinon 8mm lens with an integrated lenshood that I picked up on craigslist.  If you are looking to do the same here are some tips on how to best tackle the project yourself.

What You’ll Need To Modify The Lens

You don’t need much to get this project completed.  With the right tools it will take about 30 minutes from start to finish.  Before you begin I suggest you collect the following items.

  • Good strong pair of kitchen shears
  • Small plastic sandwich bag, or sheet of plastic wrap
  • Small computer screwdriver (as small as you can find)
  • Pocket knife
  • very find sand paper

Remove the front Lens Element

Removing Front ElementAs a first step take a look at the convex front lens element. You’ll want to remove this element before you starting shaving the lenshood back to ensure you don’t damage the lens.  To do this look for two small holes around the ring at the edge fo the lens.  Use a small screwdriver and insert it into one of the holes.

Gently use the screwdriver to turn the lens in the counterclockwise direction.  If you are having difficulty try to angle the screw driver slightly to allow you to apply more force to unscrew the element.

From my experince it doesn’t take too much force to get it started.  After you have the element unscrewed, slightly tip the lens on edge and the lens element will fall out. For now, place the lens element on the side somewhere where it won’t get in the way.


Protect the Internal Lens Elements

Exposed Internal Lens ElementThere are several videos out there that show someone completely disassebling their lens to make this modification.  You can of course follow that approach and it is probably best if you want to maintain the cleanest most dust free conditions possible.  For me, since this is just a hobby project, I was not as concerned, or as interested in fully disassembling the lens.  For my modification I simply stuffed a small sandwich back over the exposed internal element.


Trim the Rokinon 8mm Lens Hood

Brian-Opyd-Photography-600-4Next you’ll focus on making the brunt of the modification.  Take a pair of strong kitch shears and start to nibble off small strips of the lens hood. keep working your way around the lens hood until all the lens hood petals have been trimmed down to the saddle points in the lens hood.  I am defining the 4 saddle points at the lowest points on the lens hood prior to the modification. These points are flush with the front element.


Sand Any Rough Edges

After the majority of the cutting is done, I used a small piece of very fine sandpaper to sand down any rough edges on the trimmed surface of the lens hood.  This is primarily a cosmetic step.  By sanding you create a more finished edge and is good to remove burs.

Before replacing the front element also take the opportunity to wipe out any debris or dust from the inside of the exposed lens that resulted from your work.  I like to use a small soft eyeglass cleaning tissue for this work.  I use the individual wrapped alcohol based wipes. They work great.


Replace the Front Element

Modified Rokinon 8mm Fisheye LensReplace the front element using the opposite process you used to remove the element.  First slowly hand tighten the element by srewing it into the lens body.  When you can not longer hand tighten it, use your screw driver inserted in the small hole in the retaining ring to provide a little extra torque.

You should be ready to attach your newly modified lens to your camera body and test it out.

One final thought.  With the modified lens hood your old lens cover  won’t work well.  I like to use a small lens bag to store the modified lens.  I have a Canon branded lens back from an 24-105mm lens that works great.  If you are in need of something you may also find plenty of aftermarket lens bags on for example.

If you have any questions, or recommendations based on your won modifications leave a comment. I’d love to hear from you.

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One Comment

  1. Rourou December 11, 2015 at 10:30 pm #

    – You are so cute going out on a mini adventure like this! That last shot of the trees blows my mind. I never can find scerney as beautiful as you do Jen.

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