Five Megapixel Varifocal Lenses: Lessons from an Archived Optical Bench Test

A camera's pixel count does not guarantee that its lens resolves useful detail across the image. Focus uniformity, focal range, distortion, aperture, and sensor coverage all affect the result. An archived optical-bench comparison of five varifocal lenses illustrates why those characteristics should be considered together.

The comparison covered lenses described as suitable for five-megapixel cameras. This article preserves the reported equipment, method, and observations as historical material. It is not a new Smart Link Academy test, a present-day buying ranking, or a claim that the experiment took place in the United States. Historical prices and promotions are not carried forward as current offers.

What the optical bench was intended to measure

The reviewers used an optical projector and test patterns to assess resolving capability and image quality across the field. The arrangement supported different lens mounts through suitable adapters, including C, CS, and smaller threaded formats. Mount compatibility and correct spacing matter: an adapter that physically fits does not automatically establish the correct optical geometry.

For lenses with an automatic iris, a camera was used to control the aperture; it was not the imaging device for the projected-pattern assessment. The test sought to examine performance with the aperture open. This is useful because stopping a lens down can change aberrations and depth of field, potentially concealing weaknesses seen at maximum aperture.

The setup kept the projection geometry and screen arrangement controlled. However, the samples had different focal ranges. A common distance or setting is not automatically an equivalent comparison of field of view, magnification, and every operating condition.

Line pairs are not the same as a megapixel rating

The report discussed resolving power in line pairs per millimeter. If D is resolving frequency in line pairs/mm and L and W are the relevant image dimensions in millimeters, a simple sampling estimate is P = 4 × D² × L × W pixels. This assumes two samples per line-pair cycle along each axis. It is an illustrative sampling relationship, not a certification of complete camera performance.

The source quoted a roughly 44.23-megapixel equivalent for its projector assumptions. That number depends on the dimensions used and should not be presented as a universal property of a nominal sensor format. Nominal optical formats do not directly state the exact active width and height.

Contrast at the resolved pattern, field position, focus, sensor sampling, and processing all affect useful imaging performance. An optical bench can reveal lens differences without guaranteeing that a particular camera-and-lens combination will deliver the same result.

The five samples and reported measurements

The table below transcribes the archived comparison. “Reported result” is the review's megapixel-equivalent assessment, not a new independent certification. Distortion figures are the reported magnitudes at the widest setting; they should not be interpreted as identifying the direction of distortion.

What the reviewers observed for each lens

Hikvision HV4510D-MPIR

The report described relatively even focus across the field and focal range. It noted aberrations and a housing combining plastic construction with a metal mount. The table's 9.50% wide-setting distortion should remain visible in the assessment rather than being replaced with an unqualified description of negligible distortion.

The listed half-inch coverage also matters when pairing the lens with a camera. Using a smaller active sensor area changes the captured field of view. It does not make the focal length itself change.

Fujinon DV4x12.5SR4A-SA1L

The Fujinon was the largest sample and occupied a higher-cost position in the historical review. Its 12.5–50 mm range is a 4× ratio, not almost 5×. It served a different framing role from the shorter focal-length samples, so it should not be judged as if all five lenses covered the same view.

The review assigned it a six-megapixel-equivalent result and reported edge-focus limitations in parts of the assessment. Its lower listed distortion did not mean distortion was impossible. Longer focal lengths can help place more pixels on a distant subject, but face or license-plate identification still depends on framing, exposure, lighting, motion, and the complete system.

Unidentified 3.3–10.5 mm sample

This sample had reportedly been obtained at an exhibition in China, and its manufacturer could no longer be established. That provenance should remain explicit rather than being converted into a fictional domestic product. The reviewers reported five-megapixel-equivalent resolving performance with some edge-focus and aberration concerns.

An untraceable sample is useful as an optical observation, but it is a poor basis for a reproducible purchasing specification. Without a reliable manufacturer and model, a buyer cannot confidently obtain the same revision or evaluate support and quality consistency.

Evidence Foton 2.9–10 mm

The listed 2.9 mm wide end was the shortest focal length among the samples, although actual field of view also depends on sensor dimensions. The reviewers described distortion and aberrations and reported difficulty achieving focus at the long end of the tested range.

That difficulty is a finding about the sample and setup. It does not by itself prove that the manufacturer misstated focal length or that every lens of the model behaves identically. Mount spacing, test geometry, adjustment, and sample condition warrant investigation before assigning a cause. A smaller listed sensor format also does not establish a universal price or low-light advantage.

Kowa LMVZ3510IR

The Kowa used a manual iris. The report described relatively even focus and noted aberration in the central region. Manual aperture control can be appropriate where lighting and exposure requirements are controlled; it should not be dismissed as inherently obsolete.

For a site with changing illumination, determine whether the complete camera and lens arrangement provides the exposure behavior needed. The presence of an automatic iris is one design feature, not a guarantee of better images in every situation.

Apply the lessons to a current installation

The archived review found all five samples capable of its stated five-megapixel target, with differences that the headline rating concealed. That does not establish a present-day recommendation or guarantee performance on another sensor. Check the exact mount, image-circle coverage, back-focus requirements, aperture control, and intended visible or infrared operation.

Test focus at the wide and long ends, including the image edges, under the lighting the installation will use. Compare distortion against the task: an overview and a measurement-oriented application may tolerate different amounts. Evaluate the full camera output with moving subjects rather than relying only on a projected stationary pattern.

When comparing security cameras and system equipment, treat the lens as part of the imaging chain. A suitable focal range and consistent usable detail matter more than assuming every lens carrying the same megapixel label is interchangeable.