Test pictures: Olympus 8mm versus Panasonic 7-14
About domes Fish-eye lenses such as the Panasonic and Olympus 8 mm will benefit most from small radius domes (like a 4-inch hemispherical dome), enabling to focus on a virtual image close to the front of the dome (say 10-15 cm). Ultra wide-angle rectilinear lenses (such as the Panasonic Lumix -7-14), however, are said to benefit from larger radius dome ports, such as an 8-inch dome port, more suitable to focus on objects at greater virtual distances (like 30 cm or more). Examples are the Aquatica SW8 and the AOI DLP 08 (see a test of the Panasonic 7-14 with the Aquatica SW8 dome UWphotographyguide). Another port specifically recommended for the Pana 7-14 is the ZEN WA-100-EP714 Pen Dome. Notice that these ports use only a segment of the much larger hemispherical domes, which makes them substantially smaller and lighter without affecting the optical quality. So, a port advertised as a 100 mm dome port (like the ZEN port) is not a half spheric dome with a radius of 5 cm, but a 10 cm wide segment of a larger dome with a radius of 10 cm. The segmented domes will need an extended port, to align the base of the dome port with the nodal point of the lens. Rectilinear super-wide lenses are normally recommended to shoot larger objects underwater, such as UW landscapes and sharks, while the fish-eye lens seems optimally suited for CFWA images, with objects often at very small distances like 10-20 cm. Although there have been some discussions on the merits of this lens in the underwater world, tests of the ability of a rectilinear super-wide lens to focus on objects at such small distances underwater are rare. So I thought that some top-side and wet comparative tests between the Oly 8 mm fish-eye and Pana 7-14 might throw some light on this matter.
Specifications: Panasonic 7-14: diag. angle: 114-75 deg. min focusing distance: 25 cm, max aperture F4, length 83 mm, weight 300 g. Olympus 8 mm, 180 deg angle of field, min focusing distance 12 cm, length 80mm, weight 315 g.
Top-side tests. Here I compared the Olympus M. Zuiko 8mm 1:1.8 fish-eye lens with the Panasonic zoom 7-14 rectilinear lens (alias Lumix G Vario 1:4/7-14 ASPH) using a top-side home environment (see for the hardware the upper left picture below; the object used can be best seen in the pictures 5-8). The camera was the PEN E-PL9, without a dome port on the housing. My question was to find out, albeit in a crude manner, the ability of the Pana lens to focus on objects at small distances. Pictures 2-5 taken with a flash-lit foreground and a background illuminated by ambient light. Settings: 1/60 @11.0 ISO 200. Pana zoom set at 8mm. D-200 strobes set at Manual -4. The distances between the lens and the center of the object were 20 and 30 cm, respectively. Pictures 6-7: taken hand-held with natural light at 20 cm. 1/60 @5.0 ISO 200. My first impression is that the Pana zoom lens at 8mm (labeled Lumix in pictures 4-5 below) focuses rather well on short distances (varying between 10 and 25 cm of the front/back of the object with the center at 20 cm distance from the lens). Pictures taken with natural light also showed little difference, except the somewhat greater brightness of the Oly shots.
Wet test Pictures 8-11 were taken in a wet plastic tank using a FIXneo Mini 1000SW light placed on top of the AOI housing. Both lenses have about the same physical length. I used a mini 4-inch half-spherical dome with a 24 mm extension ring, for both the Oly fish-eye and Pana rectilinear lens set at 8 mm (notice that this small dome requires a lens that is able to focus at a virtual image at around 15 cm distance). The UW distance was 10 and 20 cm from the UW object, relative to the front of the dome. Settings E-PL9: ISO 200, 1/100, @8.0. Again, the Pana rectilinear lens (pics 10-11) showed almost the same sharpness of the objects placed at 10 and 20 cm distances as the Oly fisheye lens (pics 8-9). The limited space of the test tank did of course not permit an evaluation of the more distant and wider background of the object in focus.
Open water test Pictures 12-15 were UW landscape shots taken at the same location in the Mediterranean with natural light, but with somewhat different combos. Pics 12 and 13 were shot with the Oly 8mm mounted on a PEN E-PL5 body in a PT-EP10 housing. Settings: 1/160, @11 ISO 200. I used the 4-inch mini-dome with a 24 mm extension ring. Pics 14-15 were taken with the Pana 7-14 zoomed at 7 mm, on a M1 II body in a PT-EP14 housing and the ZEN WA-100-EP714 Pen Dome. 1/100, @11, ISO 200.
Conclusion Although the Pana 7-14 can probably not beat the legendary fish-eye zoom lens, the Tokina 10-17 with its beautiful forced perspective, I do feel the Pana has potential as a universal zoom lens in the four-thirds range. It should be able to focus not only on large more distant objects but also on small closer objects without a diopter, even behind a small dome port with the right extension ring. I also found the open water shots -with a touch of over-under- pretty nice, with little difference in the quality of the images. Although some have mentioned corner sharpness as a critical point of the Pan 7-14, I found no direct evidence of specifically blurry corners in these test shots. As expected, barrel distortion was less in the rectilinear Pana than in the Oly fish-eye