Dome Ports / over-under shots / examples

[Roger Southwick]

(Continuing from the "My Divebuddy" thread....)

Chris -- Thanks for the info on the 8" dome port.  I might give that one a try.  One thing that I like about the 6" port is that the petal-shaped lens hood somewhat protects the front of the dome, especially when things get bouncy on a boat.  It also allows the camera to sit upright on the ground, without any upward pressure being applied to the port:


Not sure how the larger port would fare when set on the ground; how has it worked with your Nikon housing?


The Canon 10-22 lens is pretty decent; haven't compared it to anything really wide other than a Nikkor 15mm, which is outstanding but in a completely different class.  No edge distortion there!  I generally use the 10-22 at 10mm, so the zoom is almost useless, but Canon doesn't have a 10mm prime yet.

I remember your over/under shot of the ice diver; very nice.  I've had success with the smaller port, but things might be easier with the larger one.  Here are some shots from Wazee last weekend; the guys were getting ready for a class and I just splashed in with shorts & t-shirt on.  My recurring problems are water spots (will try RVR aviation rain repellent soon) and some darkness in the corners from a misaligned lens hood.


John P with video camera:




John M and John P:






Tom C and Bob S:




It would be cool to dive together sometime....  I'll probably be at Wazee a few weekends this summer, but most of the time will be spent practicing for a tech trip to Isle Royale and the camera might have to stay on shore.   :'(
-- Roger

[Roger Southwick]

I received an 8" diameter Ikelite dome port from B&H Photo and tried it at Wazee a couple weeks ago.



General comparison to 6" dome

1. At 10mm, the corners of the image are a bit soft but not as "smeared" as with the 6" dome.

2. The dome seems very "naked" without a protective petal hood, which the 6" dome has.  But you don't get any dark corners from a mis-aligned hood.  You just have to be more careful to avoid bumping anything with the dome.

3. The camera has more buoyancy in the front and wants to tip backwards.  It's still a bit negative with 2 Ikelite 100A strobes and Ikelite arms.  (This whole system weighs about 25lb out of the water.)

4. The clear dome attaches via o-ring to an opaque black cylinder that attaches via o-ring to the housing.  You can't see the selected focal length through it like you can with the clear cylinder on the 6" dome -- not a big deal if you shoot at 10mm all the time.  Plus, it's an additional o-ring seal to worry about; it should be cleaned periodically, but would be easy to forget since you can just leave it in place.

5. Setting the camera down with strobe arms in an M shape works ok; you just have to lean the housing back a bit so the weight doesn't bear down on the dome.

6. It sure looks cool!  8)


Apparent differences when used for over-under shots

1. The apparent image for the 8" dome is further from the "film" (sensor) plane than it is for the 6" dome.  Focus on the above-water subject, and the below-water part is in better focus than with the 6" dome.

2. The underwater portion is magnified a bit more than with the 6" dome, implying that the angle of view is slightly reduced.

3. With the larger dome, when the water's surface isn't centered in the frame, the surface isn't curved as much and is in better focus.


Example



ps  Those neon-yellow tanks are great for finding your buddy, but they're awful in photos.