I know what you're thinking. You just received that shiny new Laowa 7.5mm f/2.0 for your MFT camera, you're all excited and jumping in joy, you grabbed the camera outside, find some nice place to do some test shots, focused the lens, took the shot, got back home, and when the files are on your computer everything looks mushy and lack details especially on faraway objects at its largest aperture, no matter how you set the focus on the lens.
My friends, I am sorry to say that your Laowa 7.5mm isn't properly calibrated. The lens couldn't focus to infinity eventhough the focus marker goes to infinity and beyond. I had the same problem too and I know some might have the same problem. Not all of the copy of this lens have the same issue though, so if your lens produce an adequately sharp picture, your lens is fine.
But fear not, today I'm going to show you how to repair it yourself. I know, you can send it back to them for a replacement unit, or wait for it to get repaired by Laowa. I took a slightly more savage route and repair it myself. This post was inspired by an article about fixing Samyang 7.5mm FE lens that someone gave to me during a conversation in a forum(here's the link).
Before we continue, let me remind you that doing this can void your warranty, and there's a very high risk of ruining your lens very badly. There's also a very high chance that doing this will introduce decentering to your lens. I do not suggest you to do this if you are not confident enough to open a lens, sending it back to Laowa is a better idea, or alternatively you can ask a professional lens repairer around your area. I am not going to be responsible for your action should you do what I'm about to show you.
So with that out of the way, let's start, shall we. Here are the tools that you need:
1. A very good, sturdy, plus-shaped screwdriver.
2. A piece of paper(the usual paper for your home printer will work just fine).
3. A roll of double-sided tape.
4. A good lighting so that you can clearly see the screws and the holes inside your lens.
5. Flat surface, a table or something.
6. Rocket blower or similar, the one that you use to blow air into your sensor.
7. Micro fiber cloth, just in case you accidentaly touch any of the lens elements.
Basically, what I'm about to do is to add something in between the lens' rear element and its holder that connects to the focusing mechanism inside the lens so that there's an increased distance from the rear element to mimic added focus rotation on the lever to the direction of infinity focus. There must be a better way than this, but for now I am adding the distance by adding just pieces of thin layer of paper.
Step 1:Put the lens on your table with the front element facing down. Remove the rear cap, and now you'll see the bayonet mount. On the bayonet mount, there are 4 screws that are holding the bayonet mount with the chassis of the lens. Remove those screws carefully. They are really tight, so be patient with them and do not use excess power as you may strip the screws and will make it harder to screw/unscrew them. There's an extra screw that screws-horizontally to the middle part of the bayonet mount, ignore that screw.
Step 2:Remove the bayonet mount, now you'll see that the rear element is being held together by 4 screws that screw the rear element into the middle part of the lens that has something to do with the focus lever. Remove those 4 screws. Careful, avoid touching the glasses, they are difficult to clean. Ignore the screws on the outer part of this section, just remove the 4 inner screws that are holding the rear elements.
Step 3:Once you unscrew those screws, take the rear element, flip it around so that the rearest element is facing down, and put it on the table. Put some microfiber cloth between the table and the rear element, so you can minimize the chance of the rear element gets scratched.
Depending on how bad your mis-focus is, you may need to layer the pieces of paper, or use slightly thinner paper. On my case, on the infinity mark, at f/2.0 only objects that are about 2 to 4 meters away are in focus. On the maximum rotation of the lens, only objects that are about 3 to 5 meters away are in focus. I will need to get at least to 4 or 5 meters so that it can reach optimal hyperfocal distance and get everything from that distance to infinity in focus.
In my case, a single layer of paper is enough. If your lens focus only to about 1 meter or less, then it's a good idea to stack multiple layers of paper, so cut more pieces or fold the 4 pieces so that they mimick stacked layers of paper. This is all just approximation by the way. If you only need the lens to focus a hair further, then don't use the regular home printer paper, use something thinner instead. You get the idea.
Now cut 4 small pieces of paper about 0.5cm x 0.2cm, and put some double tape on one side. Put these 4 taped pieces of paper to the outer plate that has the screw holes on the rear element. Put them on the surface that doesn't have the screw holes. Make sure that all pieces of paper have the same uniform thickness, otherwise you could cause some serious decentering on the lens. Remove the protective layer of the double sided tape.
Step 4:Blow some air with the rocket blower to the inner core of the main part of the lens, where the rear element should be, and remove any dust that might have entered that part of the lens. Now place the rear element back to its place, and screw the screws back together. After you add the pieces of paper, you might need to screw the screws more carefully.
Step 5:Again, blow some air on the surface of the part of the lens where the bayonet mounting should be, and remove any dust that might have been there. Now place back the bayonet mounting, and screw the screws back together.
Step 6:Again, blow some air on the bayonet mount and the rear element to remove any dust on it, and then mount the lens to your camera. Try the fixed focus and see how it performs. You might need to re-do the whole thing and adjust the thickness of the pieces of paper until you get the focus to focus properly to infinity, not "to infinity and beyond".
Alternatively, if you are lazy and don't mind innaccurate focus markers, you can just find the new infinity focus point and mark it yourself with a pen or scratch it permanently using blade. The way to do this is to focus on an object that is faraway, at least 5 meters away from you, at f/2.0. Mark the focus position on the lens at the point where your objects are at the sharpest focus. That's it! Now everytime you shoot, just focus to that mark, and you'll get anything from 5 meters to infinity all in focus.
I hope you find this post to be useful. Cheers and God bless you! :)