Megapixel Monsters, comparing the Canon 5Dsr to the Sony A7Rmk2 for UW Photography



The 2 current megapixel champs in Full Frame, 35mm sensors are the Canon 5Dsr and the Sony A7Rmk2.  The Canon specs out at 50.6 Megapixels (8688 x 5792) and the Sony at 42MP (7952 x 5304).  While the megapizel count seems to favor the Canon, a look at the actual pixel differences between the 2 sensors shows that the difference in both the horizontal and vertical pixel count is only 736 pixels horizontally and 488 vertically.  In the grand scheme of things, the difference isn’t all that great.  Other websites have debated the specs of these 2 cameras enough.  This comparison report isn’t about the imaging capabilities of each body (they’re both amazing), it’s how they are when used side by side in the underwater world.

The Gear Used:


  • Canon 5Dsr
  • Canon EF 100mm f 2.8L Macro
  • Sigma 15mm f2.8 Fisheye


  • Sony A7Rmk2
  • Sony FE 90mm Macro
  • Sony FE 28mm f2 with Fisheye conversion lens
  • Metabones IV EF-E Mount Converter with latest firmware

(Much thanks to Sony Canada & Rob Skeoch for graciously letting us use the Sony camera and lenses).  The Metabones Adapter was lent to us by Aquatica.


  • Aquatica A5Dmk3 Housing (yes, the sr fits) though the new A5Dsr does have additional options for Ikelite TTL triggering and the ISO lever is now included and not an option as it is on the mk3 housing. The housing is owned by SLS Photo.
  • Aquatica A7Rmk2 Housing with the new Optical Trigger. This housing was lent to us by Aquatica.
  • Sea & Sea YS-D2 strobes on the Canon, YS-D1 with the Sony.


Below is a photo of both systems assembled with the respective macro lenses.  We would have liked to have matching sets of arms but there was only so much we could lug around with 2 x 50lb bags.  We settled for using the Stix buoyancy collar on the Sony.  First of, it’s easy to see even with the collar that the Sony housing is noticeably smaller than the Canon’s.  Detailed descriptions for each housing can be found here for the Canon and here for the Sony.

One thing to note though is that the controls on the right side of the Sony housing tend to stick out more than the Canon’s and if you have larger hands then we do highly recommend getting the grip extension that Aquatica offers as an option, the extension moves the handle out enough so that your fingers don’t feel cramped up.

Now for some images, we won’t be showing 100% crops of the images, both systems produced beautiful, LARGE files.  The Canon’s CR2 files were in the low 50MB range while the Sony’s were in the low 40MB range, though Sony does apply a lossy compression to their .ARW files.

Canon 5Dsr:


Taken with the 100mm f2.8 L IS Macro


Taken with the 100mm f2.8 L IS Macro


Taken with the Sigma 15mm Fisheye and the Aquatica 4″ Mini-dome

Sony A7Rmk2


Taken with the Sony 90mm f2.8 FE Macro


Taken with the Sony 90mm f2.8 FE Macro


Taken with the 28mm f2.0 and fisheye conversion lens, Aquatica 6″Acrylic Port


We’ve been shooting Canon for about 20 years now, the interface and button layout vary little between body to body so using the camera and the housing was like putting on a well fitted suit. Everything fell into place and we didn’t have any issues using the camera and housing.  Aquatica as usual, did an outstanding job in the control layout and changing settings was a breeze.

The Sony isn’t entirely new to us as we’ve been using the Sony mirrorless system since their introduction of the NEX-5 and we published a review of the AN-5n housing.  The user can pretty much program any function to any button on the camera and thus the housing. A really important one is being able to toggle the viewfinder and the rear LCD.

Both systems were set to use back button AF and this made composition easier since you could lock the focus on your primary subject then recompose.  The Sony does have a lot more AF points than the Canon but we found that moving the focus point using the joystick to be lots slower than the focus/recompose method.  It’s not impossible to do, and actually if the subject wasn’t something that moved quickly, then we did move the focus point around.

Lens Use and AF Speed

There’s not much to say, both systems, using the native mount lenses focused extremely fast and accurately. For underwater use, the 90/100mm macros and the fisheye lenses will pretty much do for 95% of UW shooting, both companies offer a 16-35 f4 zoom that will be a great large critter lens.  The Sony does lack teleconverters so being able to go into super macro will be more challenging until a suitable set of TC’s come out.

We did do an AF fine tune on our Canon 5Dsr but since the Sony uses both Phase and Contrast Detect AF, this camera didn’t need it.

Using the Metabones did take a bit of work, the Sigma 15mm EF mount wouldn’t AF at first, however a quick update of the adapter’s firmware fixed the issue.  The lens did focus slower than when it was mounted on the Canon. Luckily, fisheye lenses don’t require too much movement so while there, the difference was negligible.  The image below was taken using the Sigma and the Aquatica 4″ Minidome.  In fact, we preferred using the Sigma and Metabones rather than the Sony 28 with Conversion lens because we were able to use the Aquatica Mini-dome and the small dome allowed for more forced perspectives.


Rhinopia and Photographer, A7rmk2, Sigma 15mm FE with Metabones.

Dynamic Range:

Much has been written and bitterly argued on the forums on how much better the new Sony back illuminated sensor would be compared to the Canon’s.  This might be the case when one is shooting something where an extra stop or so in the shadows come in to play. There were instances that shadows were better handled by the Sony, however when shooting underwater (in our preference anyway), the use of strobes, does negate the shadow regions.  What we did notice in some sunburst images is that where the Canon would render the sensor bloom as a cyan-ish fringe around the white blown out sun ball areas, the Sony would render it as more of a grey fringe.  Both look OK to our eyes but that was what we noticed most.

Battery Life:

This issue was what plagued us the most.  The 5Dsr would easily last through 2 days of intensive shooting before needing a recharge though we usually swapped out batteries after the last dive of the day.  The A7Rmk2 though would require a battery swap after no more than 2 dives.  We weren’t even shooting video and were very careful not to do too much chimping underwater.  Sony recognizes this by including 2 batteries with the camera, but a fully charged battery is useless on the diveboat if the battery dies in the camera underwater!  So if you plan on shooting video (we didn’t, we’re photographers, not videographers) it’s best to have a full battery for every dive, for still shooters, then the battery should be ok for 2 dives.


Both systems would provide stunning images in the hands of a capable shooter. Be aware that one cannot fault the camera if you come back with crappy images.  These systems are just that good.  The only change I would have done was to outfit the Sony setup with the YS-D2s as well.  The improved recycle time, audible ready beep and better control knobs are a worthwhile upgrade.  Aquatica does include their new optical trigger with the A7Rmk2 since the camera doesn’t have a pop up flash.  This allowed shooting at 5fps tying the 5Dsr.  Both cameras were used in Manual Mode with Manual Strobe Control.

I was sad to see the Sony head back to Sony HQ, it did make for a nice, tidy package with big features..for the body, but even Sony can’t change the laws of optics and lenses that can over the size of a FF 35mm chip need to be of a certain size and there is definitely no savings in size there.  Same goes for the housing, the housing itself is smaller but you are still required to use the same domes as a FF DSLR user needs.  Price wise, the Sony and Canon less than 10% apart, same goes for lenses.  So, maybe for a DSLR shooter, there is not perceived advantage on going with a FF mirrorless system, but for someone who’s upgrading from say the Sony RX100, Canon G Series, then I would definitely recommend the Sony as a fully capable underwater setup.

That’s all she wrote!



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