Optics & Photography
Wide Converters

Epoque DCL-30 wide-angle converter

The Epoque DCL30 comes in a version which has concentric M46 and M67 filter threads.  The test pictures below were taken using a Canon Ixus 115 camera in an ikelite Ultra-compact housing (2.2" diameter flat port with M46 filter thread). Pictures taken using the camera in air, and underwater via the ikelite housing are given first for comparison purposes.  

Canon Ixus 115 and ikelite housing
12 Mp 1/2.3" CMOS.
4000 × 3000 pixel JPEG output.
4× optical zoom 28 - 112 mm (35 mm equiv.)

Test conditions
Zoom setting: full wide.
35mm equiv. f = 28 mm.
Aperture: f/2.8

Underwater lighting:
2× ikelite Pro 2800 LED video lights.

Note: In order to make corner detail images comparable to those given elsewhere, the pictures were resized to 5 Mp (2582×1937) before cropping.
IXus 115 test configuration

Ixus 115 camera in air (no housing, natural daylight, equiv f = 28 mm))
ix115_28 ix115_28dt

Radial correction
ix115_28cor ix115_28cdt

Pano Tools
radial correction

Ixus 115 camera with flat port (equiv. f = 28 mm)
ix115fp28 ix115fp28dt

Radia correction
ix115fp28cor ix115fp28cdt

Pano Tools
radial correction

Epoque DCL-30 Epoque DCL-30 M46+M67
concave Magnification: 0.59×
Configuration: 4 elements, 4 groups.
Dimensions /mm: 96.4 Ø, 52.5 L.  
: 595 g air, 345 g UW.
Material: Optical glass, Al alloy body.
dot_bu Max depth: 60 m

Camera lens: 28 mm f/2.8
dcl30_ix115 dcl30_ix115dt

Radial correction
dcl30_ix115cor dcl30_ix115cdt

Radial correction

Collected radial correction coefficients - Epoque DCL-30 with Ixus 115 camera
Lens system magnif
FOV Geometry Aberration
a b c a+b+c Δdred Δdblue
Camera + flat port   54.3° 0 0.03 0 0.03 -0.001 0.005
Camera 1 75.3° 0 -0.013 0 -0.013 0.0005 0.0005
Port (f = 28mm)     0 0.043 0 0.043 -0.002 0.0045
DCL-30 0.59   0.015 -0.08 0 -0.065 0 0.003

The DCL-30 gives significant correction for the flat lens port, but there remains a considerable blue-yellow fringing even though the adapter is being used within its design limits. This is consistent with the lens entrance pupil being placed some distance behind the port at the wide-angle zoom setting; i.e., it is not a fault of the lens, it is a limitation imposed by the 4× zoom range of the camera.

David Knight.
Pictures by Steve Knight.

© David W Knight & Stephen D Knight 2012.

Optics & Photography
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