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Canon EF 11-24mm f/4L USM Lens Support

The Canon EF 11-24 f/4L USM is an incredible lens, both in terms of wide angle field of view, and in how amazingly well the distortion is controlled at focal lengths this wide.  Canon has seriously upped their lens design game, and some of my favorite optics from any manufacturer (including Zeiss and Leica) are the Canon 24-70 f/4L, 100mm f/2.8L IS, 8-15 f/4 fisheye and now the 11-24 f/4L.


The assembled rig.  Notice focus & zoom control at the left handle, perfect for video use!


The lens is extremely large, and requires extension rings and dome ports with a large internal diameter.  The original Nauticam N120 system could accept lenses up to 98mm in diameter. The larger design now used for many of our extension rings and dome ports enables lenses up to 109.5mm to be used.  This is very exciting, as it also accommodates the previously incompatible, but fantastic Zeiss ZE and ZF.2 15mm /2.8 lenses!

Paradise Found, East of Flores. All the underwater wide angle shots were with the Canon 11-24 and a Canon 6D.


Two compatible N120 dome ports for the 11-24

N120 250mm Optical-Glass Wide-Angle Dome Port II SKU#18815 (This is the most optimized for the 11-24mm) and uses a 50mm extension ring. Use this port with the following components.
N120 Extension Ring 50 SKU#21150 (109mm from SN A213191 and later)
C1124-Z Zoom Gear SKU#19550 is required to operate the zoom function.

Or the second option:

N120 230mm Optical-Glass Fisheye Dome Port II SKU#18812 This uses a 70mm extension ring. Use this port with the following components.
N120 Extension Ring 70 SKU#21170 (109mm from SN A201966 and later)
C1124-Z Zoom Gear SKU#19550 is required to operate the zoom function.
N120 Extension Ring 70 with Focus Knob SKU#21271
C1124-F Focus Gear SKU#19551 is required to operate manual focus.
C1124-Z Zoom Gear SKU#19550 is required to operate the zoom function.

Nauticam Cinima housings use different zoom and focus gears.

RC1124-Z Zoom Gear SKU#16315
RC1124-F Focus Gear SKU#16316

It is really important to have a frame of reference in mind when evaluating a lens this wide…  Corner softness is going to be a fact of life, and it can be controlled by stopping down, and keeping detail out of the corners.  You can also crop in post, or even better crop in camera by zooming in a bit in situations where you think soft corners might be distracting.  This is just an inevitable compromise associated with getting this wide without fisheye distortion.

My methodology here is to compare the lens to known quantities that are popular for underwater imaging, and simply determine if 11-24mm is better or worse. I’ll only compare like focal lengths, it just isn’t fair to compare 11-24mm at full wide with a narrower lens. This means that 11-24mm wins by default at 11mm, as there is no other currently available non-fisheye lens that is this wide.  

Our test chart has been upgraded to a new, stiffer material that stays pretty flat in the water.  Occasionally water movement would flex the chart, and cause what appear to be uncharacteristic distortions.  This could influence some of the sharpness judgements as well, but in all the test shots I see that the corner performance is about equal on all four corners, which is acceptably accurate for me. 

Corner softness is the easiest defect that pops up behind a dome to detect, and you’ll see examples here.  The tests are done at f5.6, which is actually a pretty stressy aperture.  The results are dramatically improved by stopping down a bit. 

Compared to the Canon 14mm f/2.8L II

This is a lens I have always really wanted to like, but could never find the kind of in water corner performance I was after.

This isn’t the greatest example, as there was clearly some flex in the chart that makes it appear that there is distortion that doesn’t actually exist.  Both shots exhibit some softness, even at this more distant reproduction.

Here are corner crops (well, zoomed in lightroom actually, then screen grabbed).   

And here is the same chart, from about a foot away.

with corner crops:

I think it is pretty safe to say that 11-24mm is better, and better by a significant margin in the closer focusing situations.  

Compared to the Canon 16-35 f/2.8L II

This is one of the most popular wide angle lens commonly used with Canon full frame cameras, and is used in many stunning wide angle images.  Performance isn’t perfect, but the wide field of view and overall good image quality has made it very popular on full frame.  

And the corner crop:

And now the same lenses, but closer to the chart:

And corner crops:

This one really surprised me…  Neither lens has a Lightroom Lens Correction or CA adjustment applied, so these are straight out of the camera.  I can’t believe how much purple fringing is apparent in all of the 16-35mm /2.8L II test, and how well controlled it is in 11-24mm.  I don’t see a tremendous difference in corner sharpness in either test.  Maybe 11-24mm is a bit better? 

Performance at 11mm

And now, the moment we’ve all been waiting for.  There is nothing to compare 11-24mm to at 11mm, so it will have to stand here on its own.  

Corner Crop

Close focus:

and Close Focus Corner Crop:

Corner softness certainly exists, but I’ve seen a lot worse! In situations where it is possible to stop down, or subjects are in blue water, I think the entire lens zoom range is usable.


I’m very encouraged by these results.  I see that 11-24mm is clearly better than Canon 14mm /2.8L II at 14mm, and as good or better at 16mm than 16-35mm f/2.8L II.  At 11mm, the angle of coverage is over 10 degrees wider than 14mm, and the ability to zoom out to 24mm is nice to have with skittish subjects or to crop out distracting backgrounds in camera.  There isn’t any distracting fisheye distortion, causing curved water surfaces or overly bulbous centered subjects.  Close focus is good enough for some interesting close focus wide angle shots, too!

Now, for some question and answers...

The results are good, but what are some potential issues?

Lens flare is also a reality with any optic this wide, and is something to be aware of in real world use.   The lens is big, heavy, and expensive.  24mm might not be long enough for skittish critters.

Is this a good choice for RED Dragon 6K? 

Yes, and I don’t know of a better wide angle optic for this camera in its 6k mode (slightly smaller than Full Frame 35).  16-35mm and 8-15mm /4L have been my favorites for this format in the past, but 8-15mm induces fisheye distortion that needs to be managed in framing, and 16-35mm just isn’t wide enough for a lot of wide shots.  11-24mm is perfect!  Much of the corner smushiness in these shots won’t be apparent, falling outside of the recorded frame when shooting 6K.

Should I sell my 16-35mm if I buy 11-24mm?

I’m not sure I’d run off and do that…  That range from 24-35mm is a pretty useful one, especially with skittish big animals.  16-35mm also has a front filter thread, making it more useful for use with polarizers and neutral density filters for topside shooting. It is also a lot smaller…  11-24mm will handle well in the water, but I can see a lot of situations where I wouldn’t want to carry it around topside.

I’m an APS-C, user, is this lens for me?

I’d say probably not for most…  It is probably a bit sharper overall than the Canon lenses like 10-22mm /3.5-4.5 or 10-18mm STM that are designed for the smaller APS-C sensor, but my feeling is that it is only slightly sharper.  Those lenses are a fraction the weight, and something like 1/6 the price of 11-24mm.