Canon 8-15/4L Fisheye and Thoughts on Domes

Fisheye lenses have long been my favorite optics for underwater photography. They are sharp (even in the corners), focus close for great close up wide angle possibilities, and enable the use of travel friendly small dome ports. In the old days an extremely difficult choice was required before every dive. I traveled with a Nikon 10.5 f/2.8 DX Fisheye (180 deg diagonal field of view) and a Sigma 15mm Diagonal Fisheye (110 deg diagonal field of view). The 10.5 was best for most of my shooting on a reef, but wonky fisheye distortion pops up from time to time, and a hammerhead fly by at 6' away looked look a guppy on my monitor. The lens was just too wide for even a big subject at that distance. Sigma's 15mm was better for skittish subjects, and didn't distort other divers in the frame as badly, but I missed the really wide field of view. Then along came a fisheye that could zoom!

The Tokina 10-17, available for both Nikon DX and Canon EF-S cameras, is by all accounts a great lens for underwater photography. This lens is akin to having my two 'old' favorite lenses in one, the ability to switch between them at will, and a whole new range between the extremes to explore! The 10-17 focuses very close, allowing travel friendly small domes to be used. By getting very close with a small dome tiny critters can appear big in the wide angle frame and complimentary secondary subjects like divers, boat silhouettes, and sunballs add another element of interest to the shot. The Tokina lens is very sharp, but the build quality could be better, and there is more purple fringing than I'd like to see (but typical of a lens at this $600 price point).

The New Canon 8-15 f/4L Arrives

Canon EF 8-15 f/4L and Tokina 10-17 f/3.4-f/4.5

Canon's announcement of a new fisheye zoom lens last August (2010) actually didn't excite me too much at the time. After using the Tokina 10-17 for the past four years I didn't see significant room for improvement for cropped sensors, but we felt obligated to get the lens in a pool as soon as possible to evaluate image quality behind some of the Zen domes.

Thanks to quick service from the fine folks at Campus Camera, our lens arrived on Thursday. The wizards in our workshop were able to cacluate the new extension ring length required, make a zoom gear, and crank out a dive-able prototype of the Zen DP-100 by lunch time on Friday. Pretty cool!

Canon EF 8-15 f/4 uses Canon's pro level L series optics, and is built with both full frame and cropped sensor cameras in mind. Utility with both full frame and APS-C imagers is attractive for Canon enthusiasts that own both mounts. The lens has oustanding build quality, including weather sealing that makes me feel much more comfortable when changing lenses on a dive boat. 

Slow focus isn't really a problem with super wide lenses, but its USM motor is extremely fast, and focus lock is very accurate with the 7D and 60D bodies we've tested.

with Full Frame Cameras
At 8mm it projects a perfectly round 180 degree image circle on a full frame sensor, which is known as a circular fisheye effect. This basically gives a full frame user an 8mm circular fisheye and a 15mm 'full fame' fisheye with no vignetting in one lens. The circular fisheye perspective is pretty cool, but would require removing the shade from your dome port. We are going to have to do some testing to see whether or not a version of the small dome is appopriate for this lens on full frame, which will largely depend upon how succeptible the lens is to flare. Both DP-200 and DP-230 have removable shades, and can support the 8mm focal length without increasing vignetting.

with APS-H Cameras
While certainly not the most popular systems for underwater photography, the 1D Mk IV is one of the most capable systems I've ever used. 8-15/4 at 12mm becomes the first ever full frame fisheye for this system, and the ability to zoom out to 15mm gives the underwater photographer a touch of reach with more distance subjects.

with APS-C Cropped Sensor Cameras
Canon 8-15/4 offers similar utility to Tokina 10-17, but pro lens build and optical quality. 8-15 at 15mm is about 10 degrees wider than 10-17 at 17mm, but both lenses focus on the front of the dome port, so their close focus wide angle ability will be very similar. The lens has a limit switch locking in the 10-15mm zoom range appropriate for APS-C sensors.

Canon 8-15/4 offers similar utility to Tokina 10-17, but pro lens build and optical quality. 8-15 at 15mm is about 10 degrees wider than 10-17 at 17mm, but both lenses focus on the front of the dome port, so their close focus wide angle ability will be very similar. The lens has a limit switch locking in the 10-15mm zoom range appropriate for APS-C sensors.

Reference Marks Designating Full Frame Fisheye Focal Lengths for APS -C and APS-H Sensors	Limit Switch Locking in the 10-15mm Zoom Range for APS-C Sensors

Big Dome v. Little Dome

While not quite as mind numbing as debating Nikon v. Canon, I wish I had the years of my life back that I've spent trying to convince someone that bigger isn't always better in the world of dome ports. There are definitely tradeoffs, and it is ultimately up to the individual to decide which fits best in their gear arsenal. Big domes are best with super wide rectilinear lenses, no question about it. And bigger is usually better in this case. Zen DP-230 is a great match for full frame cameras with Nikon 16-35 f/4 or Canon 16-35 f/2.8L II, or cropped sensor cameras with Nikon 10-24 f/3.5-f/4.5 or Canon 10-22 f/3.5-f/4.5. Off topic, but these are the best lenses we've tested in each category, a topic for another article. Big domes are also best for split shots, making it easy to place the location of the water line, and keeping the water line thin in the frame. If you want to use a non-fisheye wide angle lens, or you want to do splits, and your budget only allows one dome, then you need a big dome. A little dome only works with fisheye lenses (ok, you could also use a short macro too, but another a topic for another article). The small size allows you to photograph small subjects that you couldn't shoot with a big dome with equal impact. This is because the larger dome simply forces you to be further away, yielding smaller foreground reproduction. The corners will probably be a touch softer in the small dome, but see for yourself below whether or not that matters. I can pack a full system set up for macro and wide angle with a mini dome in a small wheeled carry on like the Think Tank Airport International with ease. In this age of clamped down travel restrictions that is a pretty big deal.

Our Test Setup

For this test, we hung a grid chart on the wall of a pool, and placed a weighted tripod to keep the camera position as cosistent as possible. The image sensor is about 2' from the grid in all of these tests. The lower corners of the grid chart did curl back toward the camera a bit due to the slope of the pool, which could make them appear worse than they would be if the chart was completely perpendicular to the lens axis. Oh well! Our goal was primarily to determine whether or not we had the port placement for 8-15 in DP-100 correct. Since we had the gear all together, it made sense to do a couple of quick comparision shots. We wanted to see how the lens stacked up against the Tokina 10-17, and how the lens looked in DP-100 (4' diameter) compared to DP-230 (9' diameter). We used a Canon 7D in Nauticam NA-7D housing for the test, and limited the lens at 10-15mm (its range for APS-C cameras like 7D). We'll set up the 5D Mk II when we have a version of the dome sans shade in the future.

The test results are pretty impressive, and definitely illustrate that 8-15 /4L is a serious option for underwater photographers. While the corners are a bit sharper in a big dome, the image quality is perfectly acceptable for me in DP-100.

Canon 8-15 at 10mm in Zen DP-100 at f4	Tokina 10-17 at 10mm in Zen DP-100 at f4
Canon 8-15 at 10mm in Zen DP-100 at f8	Tokina 10-17 at 10mm in Zen DP-100 at f8

The Canon 8-15 has significantly less purple fringing than the Tokina 10-17, and is a bit sharper. These crops illustrate how quickly corner sharpness improves as you stop down. With 10-17 I'd typically try to hold f11 in close focus wide angle compositions. These quick pool tests indicate that a bit more f-stop flexibility will be available with 8-15.

I'm a bit surprised by the improvement in chromatic aberration, as I thought this was just a fisheye lens fact of life. Given that the Canon 8-15 costs around 3x the price of Tokina 10-17, superior performance should be expected.

I think this lens makes a lot of sense for someone who is after the best fisheye image quality possible, or a Canon user with multiple sensor sizes in their arsenal. Tokina 10-17 is still a great value for someone getting started in underwater photography, or only using the EF-S sensor size.