Inon UWL-H100 28LD and 28M67 test pictures

As sensor sizes have increased and camera manufacturers have sought market advantage by increasing the available zoom range, the change in the physical length of the lens body as the focal length is adjusted has increased. This can result in the lens entrance pupil being a long way behind the port at the maximum wide setting. Thus it is not always possible to produce a 28AD port adapter and lens combination which will avoid vignetting at f = 28. In an attempt to solve this problem, Inon introduced the LD bayonet system, which has a larger mount diameter and lens exit aperture.  28LD converters will, in some cases, work without vignetting with 24mm lenses.
     The Inon UWL-H100 lens is tested below with the Canon S100 camera (minimum f = 24mm).  For the 28LD version, a Recsea housing (for which Recsea makes both 28AD and 28LD port adapters) is used. For the 28M67 version, an ikelite housing is used. In both housings, the distance from the port to the lens is dictated by the requirement that the lens must not crash into the port at the telephoto end of its zoom range. Hence, the results from both housings are practically identical. For results obtained from a camera and housing without a wide converter, see Canon S100 test pictures .

Inon UWL H100 28LD Inon UWL-H100 28LD
Also available as M67 type 1 and II (choice of back element to port distances)
concave Magnification: ×0.6 afocal
Configuration: 4 elements, 4 groups, glass, AR coated.
cov Max FOV: 100.8° UW, 179° in air.
Dimensions /mm: 90.4 Ø, 45.4 L. Weight: 530g in air, 326g UW.
dot_bu Depth rating: 60m

Camera lens: 24mm f/5.6

uwlh100ld_24 uwlh100ld_24dt

Radial correction

uwlh100ld_24cor uwlh100ld_24cdt


Radial correction

Collected correction coefficients - UWL-H100 28LD lens with S100 camera (equiv f = 24mm)

Lens system magnif
FOV Geometry Aberration
a b c a+b+c Δdred Δdblue
Camera + flat port   60.0° 0 0.04 0 0.04 -0.0014 0.0056
Camera 1 84.1° 0 -0.015 0 -0.015 0.0012 0.0012
Port (f = 24mm)     0 0.055 0 0.055 -0.0026 0.0044
UWL-H100 28LD 0.6   0.02 -0.092 0 -0.072 -0.001 0.004

The UWL-H100 28LD shows no sign of vignetting at f=24mm with the S100 camera. The adapter offers a small improvement over the bare port; but leaves noticeable blue-yellow fringing, which is due to the fairly large distance between the adapter rear element and the camera lens entrance pupil. Cameras with less extreme zoom lenses will give better results because the port can be placed closer to the lens at the wide-angle setting.

David W Knight
Pictures by Steve Knight
© Cameras Underwater Ltd. 2012.