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SeaLife ReefMaster RM-4K Underwater Camera Review

SeaLife ReefMaster RM-4K Underwater Camera Review

July 20th, 2021

sealife reefmaster rm-4k underwater action camera review



Introducing the SeaLife ReefMaster RM-4K:

An Action Camera Designed for Underwater Photo & Video!



Everything about the SeaLife Reefmaster RM-4K says quick and easy. In fact, it's probably the simplest underwater camera we've ever used. If you're looking for an action camera that's designed for underwater environments with a couple color correction modes and easy ergonomics, the RM-4K fits the bill. We took the RM-4K diving in the cold waters of the Pacific Northwest, along with the Sea Dragon 5000F video light. The 5000F may be a little overkill, so we generally recommend shooting the RM-4K with the Pro 2000 set. We'll make this review as simple as the camera - check out the photos and videos below!


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SeaLife RM-4K Action Camera

SeaLife Reefmaster RM-4K Pro 2000 Set (with Video Light)

SeaLife +10 Macro Lens

SeaLife Screen Shield Protector


SeaLife ReefMaster RM-4K Specifications

  • 14 megapixel Panasonic CMOS image sensor
  • Captures 4K video @ 30fps
  • 1080p @ 60fps
  • Built-in color correction
  • Whopping 140° field of view with fisheye lens
  • Unique pressure lock thumb screw seal system
  • Integrated with Moisture Muncher
  • 4 button control system
  • Wifi
  • 2" LCD screen
  • JPG image capture (no RAW files)




Sample Underwater Photos

Beautiful Dynamic Range and Details in this Coldwater Reefscene captured with the RM-4K


Preparing to enter the water!


sealife reefmaster rm4k photo

This fish didn't like being photographed with the RM4K - despite the small and unassuming size of the camera


sealife reefmaster rm4k photo

The dynamic range isn't half bad! See the nice gradation of details and color between the bright and dark parts of the image?


Sample Underwater Videos


Our Thoughts on the ReefMaster RM-4K

Overall the Sealife ReefMaster RM-4K performed as expected when it came to underwater video capture, and was better than we expected in the underwater photo arena. At 14 megapixels, the photo quality is surprisingly good for such a small camera. The corners in the images are fairly sharp and the dynamic range in the photos resulted in a nice gradient from the highlights to the shadows. We did notice that the underwater white balance was a little off at times, but changing white balance settings in the camera was easy. We found that using the shallow underwater white balance mode tended to produce the best results. The lens is very wide, so you can get nice and close to your subjects for better color and detail. There is a minimum focusing distance of 12 inches, so you'll want to consider using the sealife macro lens for smaller subjects. It's important to note that when you're taking photos above water, the camera is actually so wide that you can have a little vignetting in the housing. As soon as you go underwater, the magnification behind the flat port makes that vignetting go away. 


When it comes to underwater video, we recommend shooting 4K/30p when you are filming something still for the highest level of detail. If your subject (or you) is moving a little faster, then we might recommend filming at 1080p/60fps. The electronic video stabilization does a surprisingly good job at stabilizing underwater video. Not quite as good as the GoPro Hero 9, but still very good.


The Reefmaster RM-4K is not compatible with underwater strobes, so you will need to use an underwater video light to bring back warm colors into your scene. The Pro 2000 package is more than sufficient for adding beautiful colors in both your wide angle and macro photos or video. However, if you don't want to bother with video lights, the RM-4K has two built in color correction modes that work quite well (as we mentioned before). We found the colors in our photos and videos to be particularly vibrant, with or without a light.


Given that the RM-4K is the same price as the SeaLife SportDiver Housing, we actually slightly prefer our results from the SportDiver housing with a smartphone.  We took our SportDiver Housing on the same dives as the RM-4K, so feel free to compare what you see in this review. If you have a higher-end phone like the Samsung Galaxy S20 or iPhone 12, you'll likely get better results. But if you don't want to risk bringing your phone underwater or don't want to buy a better phone and need something small, quick, and easy for your dive trip, the RM-4K is the way to go!


Learn more here:

Contact our sales department:

Phone: 310-633-5052



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