Testing: GBO InfinityLens LensesBy Benros Emata, Published Sep 29, 2010, 12:00am EDT (Research)
Ensuring surveilled objects are in focus is a common concern. In this report, we examine lenses claiming to offer a massive depth of field (MDOF), allowing objects in both the near and far fields to remain simultaneously in focus. This test evaluates GBO's InfinityLens lenses [link no longer available].
[Update 2012: GBO is out of business.]
Inside this report we'll reveal our findings based on side-by-side comparisons of the GBO InfinityLens lenses versus a commercially available lens. We provide image captures to allow the viewer to participate in the evaluation.
Depth of Field Performance
We tested the 14.0mm, 30.4mm and 52.3mm manual iris GBO Infinity lenses against a commercially available 5-50mm auto-iris lens using the same 4CIF IP camera for each trial.
In the first trial of 14.0mm GBO lens vs. 5-50mm commercially available lens we adjust the focal length of the 5-50mm control lens so that the horizontal FoV is similar to the 14.0mm GBO lens' horizontal FoV. We then adjust the manual iris so that light levels and aperture sizes are relatively equal.
We then set focus to license plate/person subjects at 20 feet (near) and capture images at the 20ft (near), 50ft (mid) and 100ft (rear) of the same license plate/person subjects. This procedure is done for both the GBO and commercial lens.
We repeat focusing at the 50ft (mid) and 100ft (rear) locations and then capture images at the 3 (near, mid, and rear) locations for these two focus points. This procedure is done for both the GBO and commercial lens.
We then repeated the same steps for the 30.4mm and 52.3mm lenses, with the following adjusted reference distances:
- 30.4mm focal length lens test - near (25ft), mid (50ft), rear (100ft)
- 52.3mm focal length lens test - near (100ft), mid (250ft), rear (450ft)
In our low-light tests we capture images of the 14mm GBO InfinityLens lens at a 1.0 Lux and 0.3 Lux level. We then repeat the procedure with a commercially available lens. We then compared the two lenses at each lux level for differences in image quality.
Related Lens Reports
GBO offers sixteen (16) models of lenses in its InfinityLens series. Lenses are available in fixed focal lengths of 3.5mm, 5.5mm, 8.8mm, 14.0mm, 16.1mm, 30.4mm, 52.3mm, and 86.0mm. Manual iris models are available at each focal length. Some focal lengths support other iris control types such as a 52.3mm fixed iris lens (IL-52-F28-C), a 30.4mm auto-iris lens (IL-30-A28-C), and a 16.1mm auto-iris lens (IL-16-F28-C). All lenses are capable of supporting a maximum sensor size of 1/2". The 3.5mm and 5.5mm lenses are available as a CS mount, while 8.8mm to 86mm lenses are available as C mount lenses (spacer allows CS compatability). Also, the 3.5mm, 8.8mm and 14.0mm focal lengths are available as an M mount lens as well.
GBO lenses provided slight to modest detectable improvements in focusing objects throughout the depth of field, in the majority of side-by-side image comparisons with a commercially available lens.
At 1.0 Lux levels the GBO lens appeared to retain a sharper focus compared to the commercial lens. However, when the lux level was reduced to 0.3 Lux the GBO lens produced a grainier/noisier image in comparison to the commercial lens.
Image captures from testing results [link no longer available] are available for download and review.
There are a few compelling disadvantages to using the GBO InfinityLens lenses for typical video surveillance applications. Firstly, the majority of the GBO InfinityLens lenses have an MSRP of $490. In contrast, a Computar (H3Z4518CS-MPIR) MP rated vari-focal 4.5mm to 13.2mm, manual-iris lens retails at MSRP $367. Another option to consider is a Tamron (M13VM550) [link no longer available] 5-50mm MP rated varifocal auto-iris lens, which has an MSRP of $360. Secondly, the InfinityLens lenses are fixed focal length, and as such will not allow for custom fitting the focal length to the application. Another disadvantage is that the majority of the InfinityLens line are manual iris, and may be an issue in fluctuating light environments.
The GBO InfinityLens lenses may be more appropriate for specialized niche applications such as license plate recognition. In installations where there are only a few license plate cameras in relation to more standard use cameras, the price difference becomes somewhat less significant.
The utility of the increased depth of field provided by the GBO InfinityLens lenses may also be more appropriately realized in applications where extensive digital PTZ functionality is relied upon to investigate events or objects within video scenes at various depths.
Physical Overview and Test Results
In this screencast, we provide a physical overview of the GBO InfinityLens series. In this overview we do not show any of the M mount style lenses, any of the 16.1mm lenses, and a couple others are not shown for brevity. See their entire InfinityLens series line-up on thier website [link no longer available]. We then show some example image captures demonstrating the differences between GBO and the commercial lens used in our testing. Finally, we present the results of the low-light comparison between GBO and the commercial lens using a wide dynamic range day/night camera. You can get a better look at these test images [link no longer available] by downloading them.
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