 |
| Image credit: Lensrentals |
The team at Lensrentals rents a lot of camera equipment. This gives the team an interesting perspective and provides them with a large enough sample size to notice if any cameras or lenses are more likely to exhibit certain issues. Even good lenses can show problems given extensive use by many different photographers. The Panasonic S Pro 70-200mm F4 OIS is one such lens. It’s a popular lens that showcases strong performance, but Lensrentals has had a couple of samples with a similar issue with the autofocus motor failing. Rather than send the lens off for repair, which can take a while and negatively affects Lensrentals’ inventory, Roger Cicala and Aaron Closz decided to take an affected lens apart and see if they could fix it themselves.
Starting from the rear of the lens, Cicala and Closz removed the bayonet and rear baffle, unveiling some screws to remove and a rubber gasket.
 |
| Image credit: Lensrentals |
After removing more pieces, they got to the circuit board. The lens uses an array bent flex cables. Interestingly, it also includes two heavy-duty grounding wires. Lensrentals writes, with a trademark sense of humor, ‘I doubt it’s going to influence anyone’s purchasing decision, but rest assured, the circuit board is thoroughly grounded.’
Near the circuit board, there are a pair of springs coming up from the internal optical image stabilization (OIS) system. The lens promises five stops of shake correction via its stabilization system.
 |
| Image credit: Lensrentals |
After removing additional sealing tape and many screws, the zoom ring didn’t want to budge. It wasn’t going to slide off the back of the lens, so it was time to refocus and start disassembling from the front of the lens. The front of Panasonic lenses is often difficult to take apart, ‘so alcohol, heat, and vigorous use of a spudger were needed.’ And in case you were wondering, ‘For those of you who want to know how you use a metal spudger without scratching glass, the answer is experience. How do you get experience? You scratch some glass.’
After removing the makeup ring and the spanner ring beneath, there is now access to six screws holding the front ring on. There’s also sealing foam to help provide a seal against dust and moisture. Next comes the focusing clutch mechanism, the aperture ring and the focusing ring itself. The lens also includes a pair of ball bearings, which ‘fit in slots and serve as rollers when the clutch is moved back and forth to change from auto to manual focus.’
 |
| Image credit: Lensrentals |
After removing as much as possible from the front of the lens, Cicala and Closz moved back to the lens’ rear and resumed taking it apart. Eventually, they got to an unusual spring. The spring has a small sensor or window or LED. Cicala and Closz aren’t sure precisely what it is, or if it’s responsible for the lens’ autofocus issues.
 |
| What is this object? Image credit: Lensrentals |
Moving on, the next element is the OIS unit. It’s held in place by thick nylon eccentric pegs and a metal bracket, which is a design the duo have never seen before – and they’ve seen a lot. The nylon pegs adjust tilt in the OIS unit. The OIS unit comes out of the lens as entire assembly. After removing it, you can see the focusing elements and the lens’ linear focusing motor. In the image below, ‘You can see the larger main sliding rod (red arrow) and the cover of the secondary sliding rod (green arrow). The other two corners of the focusing group fit into plastic corners (yellow arrows) to prevent any tilt with movement and both have soft rubber bumpers to minimize shock at the end of the focus group’s travel. You can see the tops of the two magnets at the top and bottom of the focusing group.’
 |
| Image credit: Lensrentals |
After removing more screws and finally getting the zoom ring removed, we see the inner core of the lens. The core is in two halves, like most 70-200mm zoom lenses. This Panasonic zoom lens features a thick piece of metal, which is nice to see and speaks to Panasonic’s attention to detail. Some lenses have a weak point here, which can break. After disconnecting the halves and removing more parts, it’s time to see what’s going on with the linear focusing motor.
Once the electromagnetic coils that run around the sides of the focusing group become visible, the problem is obvious. The electromagnetic coils were attached using only glue to the focusing group plastic and the glue came loose. It was still attached at one side, but one side isn’t good enough. The focusing group was tilted relative to the motor and was no longer able to move well, or at all. Lensrentals writes, ‘The reality is glue can fail under the fast vibrations of a focusing motor. We found this kind of problem in the first generation Sony and Zeiss linear motor lenses back in 2015. And a couple of years later we found that newer generations of those lenses all put cages, tabs, etc. to help hold the electromagnet in place, they didn’t just rely on glue.’
 |
| The Panasonic S Pro 70-200mm F4 OIS lens features plenty of good design choices. However, perhaps affixing electromagnetic coils using only glue wasn’t among them. Image credit: Lensrentals |
It’s worth pointing out that while Lensrentals has a pair of Panasonic 70-200mm F4 OIS lenses with this problem, that’s under 10% of their total inventory. Further, their lenses are very heavily used. You’re unlikely ever to see the issue with your own lens. However, if you do, don’t try to fix it at home. It’s a complicated disassembly.
 |
| While you may be able to take apart your Panasonic S PRO 70-200mm F4 OIS lens, should its autofocus system stop working, good luck putting it back together. Aaron Closz is shown here with all the different parts of the lens that you need to disassemble to get to the root of the AF issue. Image credit: Lensrentals |
There are many more fantastic images from the teardown and extensive details about the different components of the Panasonic Lumix S Pro 70-200mm F4 OIS lens. If you’d like to see them and learn more about the lens, head over to Lensrentals. We highly recommend checking out the full blog post. It’s a treasure trove for lens nerds.
Author:
Jeremy Gray
Source: Dpreview
