If you have a shiny new Olympus OM-D E-M10 III or possibly a Olympus OM-D E-M10 II, you may have also noticed how expensive the Olympus prime lenses are on the M4/3 format to get a decent aperture...
There are some cheap unknown brand prime lenses on ebay or amazon that seem an amazing deal!
These lenses go under the name of 7artisans, viltrox, Discover, Zonlai and a few other, but they look identical.
Although M4/3 is a "system" or a "standard" at least in the case of the 7artisans 25mm f1.8, and the Olympus OM-D E-M10 III, that is not the case...
If, like me, you bought one, thinking it would work on your M4/3 Olympus OM-D E-M10 III, you would be sadly mistaken - like me.
Someone didn't rtfm. Was it the clever lens manufacturers in Shenzhen - out to make a quick buck? Was it Olympus - shaping the camera outside the mount to interfere with 3rd party lenses, forcing you to purchase only svelte, costly Olympus lenses?
We may never know.
What we do know, however, is that we can modify the cheap 7artisans lens to make it fit!!
The problem with these this 7artisans lens that the Olympus OM-D E-M10 III camera's built-in flash rises up from around the lens-mount and causes interference with the outside diameter of the lens, preventing it from being mounted.
Not a little interference - a lot. There is just no way you could ever get it to mount.
The top part of the camera body, just above the top curve of the lens-mount is higher, and then curves outward for the pop-up flash. This top-part is where the problem is...
Lucky for us, the 7artisans lens has plenty of meat on the the outside to work on...
Step 1: Remove the Lens Mounting Plate
We need to remove the lens mounting plate.
These 7artisans lenses are made to work on different camera mounts, so they design them with an easily removable mounting plate.
BUT - first observe how the mounting plate is attached to the lens. Note the location of the red-dot lens mount indicator in relation to a fixed (non-rotating) part of the lens body. This is important for when you want to re-attach the mounting plate again!
I used a PH0 phillips screw driver. There are 3 screws to undo. They are torqued in pretty good...
I'd recommend removing the lens cap, placing the lens down-facing on a hard surface, and using a good-condition screw driver with plenty of downward force to release the screws, and avoid stripping them.
Once you have the mounting plate removed, you can remove the very thin gasket thats below it. Its feels like its ridgid and can probably break - don't bend it. Its held in place with some grease.
Step 2: Measure the Affected Area
Next we need to transfer and mark which areas of the lens is affected by the camera body.
Remember, the lens turns to mount, so we need to accommodate that degree of interference into the markings we transfer.
Start by taking off your lens.
Place a piece of paper over the camera body, making sure to line it up to the bottom.
Mark the location on the paper where the tripod-mount is. This is dead-centre to the lens mount.
Also mark the two points there the top-curve start protruding out towards the pop-up flash.
Also mark the red-dot (lens alignment indicator).
Step 3: Transfer First Interference Point to Lens Mouting Plate
Start by using some masking tape, and marking the reverse side of where the red-dot lens mount indicator is (see small piece of masking tape).
On your paper, draw a center line up from where the tripod-mount lined up with the bottom of the paper. Place your mounting plate on the paper, mounting "hooks" face-down, using the vertical line to visually divide the hole inside the lens mounting plate into two equal halves.
Align the masking tape for the red-dot lens mount indicator is to the paper.
Now, apply some masking tape to mark the right location on the mounting plate, where it matches the right-interference point on paper. You can align your tape so it points towards the virtual center point.
Step 4: Transfer Second Interference Point to Lens Mouting Plate
For the second point, we need to consider the range of motion of the lens as we mount it.
Rotate the mounting plate around it's virtual center point until the market red-dot lens mount indicator is pointing up. This is where the lens will stop rotating as you mount it.
Now, apply some masking tape to mark the left location on the mounting plate, where it matches the left-interference point on paper. You can align your tape so it points towards the virtual center point.
Step 5: Mask Up the Mounting Plate
Now that we have the left and right edges of the interference marked, we can start masking off the rest of the mounting plate to protect it from surgery.
The edge of the mounting plate has a lip. We're going to have to file that off so its flat.
Cut out some rounded chunks of masking tape and stick on the inside of the lip, and then all around to protect the mounting plate from scratches and metal filings.
Try and position the tape right up to the edge of the lip.
Step 6: File Off the Lip of the Mounting Plate
Place mounting plate on the edge of a sturdy surface, and using the a fine flat file, start filing down the lip. This is quite easy. Its made from soft aluminium!
You can give it a bit of a chamfer as to not create a sharp edge.
Try not to damage or scratch the rest of the mounting plate.
Use a fine grit sand paper to smooth it after filing.
Remove the masking tape. Use alcohol pads to clean any tape residue and metal filings.
You can now test the mounting plate on the camera - it should rotate without obstruction, and with about as much force as another lens. Be careful of forcing it all the way round. The mounting grips the plate, and you don't have much leverage to remove it... just check the clearance on the bottom. You should not be touching the camera body at the top.
Step 7: Transfer Markings to Lens Body
Place the mounting plate back on the lens body, lining up the screw holes and your initial observation of where the mounting plate's red-dot mount indicator lines up to the body.
Transfer your newly filed off lip area to the lens body with some masking tape.
Step 8: Prepare the Lens Body for Surgery
There are two areas of interference between the lens and the body. The first was the lip of the mounting plate. Now we have to deal with the lip on the side of the lens body.
Start by taping some paper over the back lens area.
Use a disposable latex glove around the outside of the lens, and tape it in place, so that you cover the inside groove at the back of the lens (now exposed since you removed the mounting plate).
Leave just the outside lip exposed.
The whole lens should now be protected from metal filings. Make sure there are no gaps!
Step 9: File Down the Outside Lens Lip
Using the file again, start to file down outside edge of the lip, only in the arc of the circumstance where there would be interference with the camera body during the mounting twist.
You only need to take down the outside edge (see diagram) and a bit from the bottom, however while I was filing away, I felt the lip became too thin and sharp, so I ended up taking most of it out.
Sand down with fine grit sand paper.
Use a vacuum cleaner to clean up filings frequently.
Try not to let any filings enter the masked out lens area.
Prepping the lens takes too much effort. There is no second try, but you also cannot test it against the body while it's wrapped up... So you need to be sure you take enough material off so it'll fit.
Step 10: Cleanup
Vacuum the outside of the wrapped lens and clean your hands from any metal filings.
Slowly start unwrapping the tape and take off the gloves.
You'll see some filing made their way into the folds of the tape. Be careful not to get any into the greased cavity of the lens, else your focus and aperture movement will be impacted.
Clean outside of lens with alcohol pad to remove any tape residue.
Step 11: Fit Mounting Plate & Touchup
Now we can replace the gasket and mounting plate. Replace screws.
(as mentioned, I took off most of the lip from the lens body).
Tough up the exposed aluminium with a Sharpie. After a few coats - you can't even tell the lens was modded without close inspection.
Test the lens - it should mount just as easy as any other lens now.
Step 12: Results!
Does it work?