This is a continuation of a series of posts on the Sony a7III. You should be able to find all the posts about that camera in the Category List on the right sidebar, below the Articles widget. There’s a drop-down menu there that you can use to get to all the posts in this series; just look for “a7III”.
The battery door of the a7III, and most other a7x cameras, is widely considered to be the camera’s weather-sealing Achilles heel. I wondered if there were some way to test the weather sealing there without destroying a two thousand dollar camera. I came up with one. The Really Right Stuff (RRS) bottom plate for the camera attaches in the following way:
- You take the battery door off the camera
- You mount the plate
- You attach the battery door to the plate.
In the a7III, the pliant (not very pliant, by my estimation) parts of the seal are on the door. The corresponding parts of the camera body are hard plastic. When the door is attached to the RRS plate, it mates with hard anodized aluminum bits that perform the same purpose. It appeared to me that the battery door on the plate would have the same weather resistance as the battery door on the camera, whether or not the plate was attached to the camera. Taking the plate off the camera would allow me to see the entry of moisture.
By the way, you might be wondering how good the weather sealing is between the top of the RRS plate and the battery compartment. It looks to be excellent. There is a broad expanse of soft material that seals with the camera around the battery door.
I set things up this way:
The plate is in a Pyrex dish. The GFX with the 120/4 macro is aimed at the plate. Two 600 watt-second strobes with softboxes light the scene.
Here’s what it looks like with a little water in the dish:
That’s fine. It stays dry as you add water until suddenly it doesn’t:
The water pours in, rapidly filling the compartment.
It appears that the flow comes from the hinge area and that the flow is mostly over the top of the hinge, which is why it takes a fair amount of water to get the floodgates to open. The RRS plate makes an effort to seal the top of the hinge, but it’s not working well. Looking at the camera itself, there is no soft material that mates with the top of the hinge, so this flooding over the top is likely to occur at least as badly with cameras that have no plate attached.
This explains why some users have reported no problems when setting the camera down on wet surfaces, and others have had flooding — it depends on how deep the water is. It is possible, and even likely, that there will be leakage with small amounts of water given enough time. I only gave the camera a minute or so to deal with the small amount of water before I increased the depth.
I went back and titrated the water more carefully and slowly and found another entry point that occurs at a lower water level than the hinge opening. Here’s a sequence showing the water entering:
Roger Cicala identified this place as problematical in his a7III teardown.