How to choose the best close-up lens for your underwater MFT rig

How many times you see practically new close up lenses being sold on eBay after sitting for years in a cupboard? Have you ever experienced the frustration of buying a close-up lens to find out it did not add anything to your set up?

There is a lot of confusion in terms of what is that you are really getting when you buy an underwater close-up lens. In most cases lenses are specified in diopters, in some other cases with a magnification factor, in few cases with the focal length.

The focal length is probably the most useful of those specification because in a traditional diopter the following formula is valid if you approximate the lens to converge in the rear element:

Working distance ≤ Focal length – physical length of the close-up lens

For example for a Subsee +5 diopter the focal length is 1000/5=200mm the lens is 32mm therefore the working distance is less than 168mm.

Now on its own this means very little. Depending on the camera we use a distance of 168mm may be a great improvement or no improvement at all.

To understand why we need to look on our camera and find the little symbol that indicates the focus distance reference mark.

While for DSLR the shooting distance is typically calculated from the front on the lens for micro four third you need to use this obscure symbol.


Once we locate the reference mark we need to identify the corresponding reference on the housing we can use the other dials as starting point. In this case the mark is approximately in the middle of the cold shoe.

When we put the camera in the housing we can then look up the specifications of the lens and calculate the minimum shooting distance. For example for an Olympus 60mm this value is 19cm.


We take note of this point and then measure the distance between the glass and the minimum working distance on land.


This works out to be around 9cm. We now need to consider that once immersed in water this distance will be multiplied by 1.33 to become 12cm.

It follows that any diopter with a focal length close to 12cm or longer is not going to be effective for our camera and lens combination. More likely we need something that can focus substantially closer or the benefit will be minimal. Assuming we half the physical working distance between the port and the subject we need something around 60-80mm focal length which considering the length of the lens itself could mean getting 2cm away from the subject.

LensOptimal Close-Up Lenses
Olympus 60mm
Leica 45mm
Nauticam CMC, Inon UCL-67, Saga +15
Olympus and Panasonic
No lens compatible
Panasonic 14-42mm II
Olympus 14-42mm

As 60mm plus
Nauticam CMC-2, Inon UCL-90, Saga +10
Inon UCL-165, Subsee 10, Subsee 5, Saga +5

The table summarises the possible lens choices for the most popular MFT lenses on the market at this time.

12 thoughts on “How to choose the best close-up lens for your underwater MFT rig”

  1. hi i have been ardently following your blog for years and have been utilizing similar equipment all through the rx100 series based on your good advice and excellent research. recently I have acquired the panasonic gh5s so was wondering if you can advise on the optimal rig setup with regards to wide angle and macro, like you did for your previous rigs. appreciate your input thanks

      1. thanks man. I am still shopping for housing and noticed your posts on wetpixel forums about the aquatica casing limitation regarding attaching a wet lens for zoom lenses. is it not better to just get a wider angle lens like a 7-14mm? currently i am using an Inon H100 on my rx100 IV setup and it seems so much more straightforward than this mirrorless setup. appreciate your advice as I am still shopping for casing thanks!

      2. hey thanks for your reply. but based on your previous recommendation in the blogs and forums I had already gotten the n85 power zoom macro port 29 is that not correct? please verify

      3. At time of writing for my first wwl-1 review dual IS was not available on any Panasonic body. Now it is and works with the 14-42 MKII it is mostly relevant for video

      4. thanks for reply. but I just submitted my order so need to change it before its too late. as Im using the GH5S which has no IBS which of the following setup do you recommend for most optimal video quality and most flexibility with regard to use of wet lenses (in my case INON UWL-H100 and M165 x2 on flip diopters):

        1. panny 14-42 PZ vario x OIS + port 29
        2. panny 14-42 mega OIS + port 35

        i am also thinking of attaching a m67-LD mount convertor instead of using the proprietary nauticam bayonets

        appreciate your speedy and as always wise advice

  2. Hi there,
    Like Ken, I have been following you and find your posts to be a wealth of knowledge in a confusing world. I have a Panasonic LX7 in an Ikelite housing and I am looking for something in the 10-15 diopter range. I already have an Inon UCL-165, and I am wondering what might work for me. I am hoping that I can use the CMC-1 or UCL-65, but I have not yet figured out if it will be physically possible or not. I think that the CMC-1 will have a min. focus distance of 52mm with the LX7. Am I correct in assuming that I need to subtract the length of the CMC-1 from that, to get my real working distance? if so, that would give me around 18-20mm. Is this a viable option, or is it too close? I assume that this is at wide angle and if I zoom in, it would increase a little. What diopter would you suggest to use with the LX7 for super macro shots?

    1. This post is really for micro four thirds. The LX7 choices can be found in my old posts for compacts. Broadly the old Inon range works fine the camera small sensor doesn’t justify newer more expensive lenses. Look in the archive for the lx7 tag

      1. Thanks for that. I did not see any references to super macro lenses for the lx7, only normal macro. That is why i wanted to ask what you recommend for super macro with lx7 because i know you used to use one and would know the best options. Im happy to get a modern lens because someday ill upgrade my camera.

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