What Happens When a Machine Vision Lens Is Too Small for the Sensor? Image Circle, Vignetting, Dark Corners and Sensor Coverage Explained

A machine vision lens can physically mount onto an industrial camera, focus correctly and still be the wrong lens for the sensor. One of the most common reasons is insufficient sensor coverage. The camera sensor is physically larger than the usable image circle produced by the lens, so the centre of the image may look normal while the outer regions become progressively darker, softer or partially unusable. In more severe cases, the corners can become obviously black because the rectangular sensor extends beyond the region the optics were designed to illuminate.

This problem is especially important for buyers searching for a machine vision lens for large sensor camera, machine vision lens sensor size compatibility, C mount lens for 1 inch sensor, C mount lens for 1.1 inch sensor, machine vision lens without vignetting, industrial camera lens for full sensor coverage, machine vision lens image circle, or how to choose machine vision lens sensor format. A lens may have the correct C-mount thread, focal length and resolution class but still fail because its supported image format is smaller than the camera sensor.

The Kyptec Automation® Machine Vision Lens collection is structured across several image-format and resolution families. The current portfolio includes 5 MP and 10 MP lenses for 2/3" formats, 10 MP options for 1" format, and 25 MP models for 1.1" format, together with multiple focal lengths within those groups. This distinction is important because sensor format is not a minor specification printed beside focal length. It defines the approximate sensor coverage for which the lens has been designed.

The central buying rule is simple: the machine vision lens must produce a usable image circle large enough to cover the active camera sensor. When that condition is not satisfied, increasing camera megapixels, changing software settings or adjusting exposure cannot fully correct the underlying optical mismatch.

What Is the Image Circle of a Machine Vision Lens?

A camera lens does not project a rectangular image. The optical system creates a circular image behind the lens. The rectangular image sensor sits inside that circle and records only the portion falling on its active area.

The diameter of this usable projected region is commonly referred to as the image circle. For correct camera-lens matching, the sensor's active diagonal should fit within the usable image circle of the lens with sufficient optical performance across the full required field.

This means sensor compatibility is fundamentally a geometric problem. If the sensor rectangle fits comfortably inside the useful image circle, the lens can illuminate the full sensor area. If the sensor extends too close to or beyond the image-circle boundary, peripheral brightness and image quality can decline. If it extends significantly beyond it, visible dark or black corners can appear.

A machine vision lens published for a 2/3" image format should therefore be interpreted as belonging to a different coverage class from a lens designed for a 1" or 1.1" format. Kyptec Automation® currently separates these classes within its Machine Vision Lens portfolio rather than presenting C-mount alone as the compatibility specification.

Why Sensor Diagonal Matters More Than Width Alone

A rectangular sensor must fit inside a circular image area. The corners of the sensor lie farther from the optical centre than the middle of its horizontal or vertical edge.

For this reason, the sensor diagonal is an important coverage dimension. A lens can appear to cover the horizontal and vertical centre portions reasonably well while still showing significant problems in the extreme corners because those corners are the farthest points from the image centre.

This explains why vignetting often first becomes noticeable in the corners rather than as a uniform dark boundary around the complete image.

When comparing a machine vision lens to a camera, buyers should therefore identify the camera's actual active sensor dimensions or sensor format and confirm that the lens is rated for that size or larger. The camera megapixel count alone does not reveal the physical image-circle requirement because cameras with similar pixel counts can use different sensor dimensions.

What Does It Mean When a Lens Is “Too Small” for the Sensor?

A lens is optically too small for the sensor when its useful image circle does not adequately cover the camera's active imaging area.

This does not necessarily mean the lens barrel is physically small. It also does not mean the lens has a small focal length. “Too small” in this context refers to image-format coverage.

A 35 mm focal-length machine vision lens designed for a 2/3" image format and another 35 mm lens designed for a larger 1" or 1.1" image format can have the same focal length yet differ in the sensor area they are intended to cover. Both may use C mount. Both may screw onto the same camera. Their optical compatibility can nevertheless be very different.

This is exactly why buying a machine vision lens by searching only for “35 mm C-mount lens” is incomplete. Sensor coverage must be checked separately.

Kyptec Automation® currently offers several focal lengths within different format families, allowing buyers to preserve the required focal length while selecting an image format appropriate to the camera sensor.

What Happens First When Sensor Coverage Is Marginal?

When a sensor is only slightly larger than the lens's comfortable coverage region, the problem may not initially appear as completely black corners. Instead, the outer image can become gradually darker or less consistent.

This is one form of vignetting or illumination falloff. The centre of the image receives stronger illumination, while the corners receive less.

For casual imaging this might be considered mainly a cosmetic issue. In industrial machine vision it can directly affect inspection reliability because algorithms often use intensity, contrast, edge response or texture information. A defect of identical physical size can appear with different contrast depending on whether it lies near the centre or near a darkened corner.

This is why full sensor coverage for machine vision inspection should be evaluated according to usable inspection quality rather than simply asking whether some image reaches every sensor pixel.

What Is Vignetting in a Machine Vision Image?

Vignetting is a reduction in image brightness toward the outer regions of the frame. It can occur for several optical or mechanical reasons, but an undersized image circle is one particularly important cause in camera-lens mismatch.

The appearance can range from gentle corner shading to strong darkening or obvious black corners.

In a machine vision application, the problem becomes serious when the intensity difference is large enough to change the behaviour of the inspection algorithm. A threshold selected for the centre may no longer work reliably in the corner. A small surface defect can have weaker contrast. Printed information may become harder to segment. Edges may be less consistent.

If the lens is fundamentally too small for the sensor, software flat-field correction may reduce some brightness variation, but it cannot restore optical information outside the useful image circle or correct severe peripheral sharpness loss caused by an inappropriate lens format.

Dark Corners Are a Strong Warning of Sensor-Coverage Mismatch

Clearly dark or black corners usually indicate that the outer sensor area is receiving substantially less usable image information than the centre.

Before replacing the lens, other potential mechanical causes should be checked, including an incorrectly positioned aperture, unsuitable adapter, filter holder or physical obstruction. However, when a lens designed for a smaller sensor format is installed on a larger camera, insufficient image-circle coverage should be one of the first compatibility issues investigated.

A buyer should compare the lens image-format specification with the camera's active sensor format. If the camera sensor exceeds the supported lens format, replacing the lens with a larger-format model is normally a more technically sound solution than attempting to hide the corners in software.

Why C Mount Does Not Guarantee Sensor Coverage

C mount defines the mechanical camera-lens interface and associated flange geometry. It does not define the diameter of the useful optical image circle.

This is one of the most important distinctions in industrial lens purchasing.

A 2/3" C-mount lens and a 1.1" C-mount lens can both mechanically attach to a compatible C-mount camera. The thread can fit perfectly while the optical coverage differs substantially.

Kyptec Automation® currently publishes, for example, the Kyptec Automation® 8 MM 5 MegaPixel 2/3" Machine Vision Lens as a 2/3" format machine vision lens, while its Kyptec Automation® 8 MM 25 MegaPixel 1.1" Machine Vision Lens belongs to the larger 1.1" high-resolution family. Both are current machine vision products, but they are intended for different sensor-coverage requirements.

This comparison illustrates why mount and focal length must never be used as substitutes for sensor-format matching.

2/3" Machine Vision Lens Coverage Explained

A 2/3" machine vision lens is designed around cameras whose active sensor fits within that image-format class.

Kyptec Automation® currently publishes several 2/3" Machine Vision Lens options, including 5 MP and 10 MP families across multiple focal lengths. For example, the Kyptec Automation® 16 MM 5 MegaPixel 2/3" Machine Vision Lens and Kyptec Automation® 25 MM 10 MegaPixel 2/3" Machine Vision Lens are both current 2/3" format options in different optical-resolution classes.

If the industrial camera genuinely uses a compatible 2/3" sensor, this format can provide an appropriate starting point. If the camera uses a physically larger sensor, the buyer should not assume the lens remains suitable merely because the C mount is unchanged.

What Changes When the Camera Uses a 1" Sensor?

A 1" sensor requires a larger usable image circle than a 2/3" sensor.

A lens specifically designed for 1" coverage therefore provides an optical advantage when the camera sensor belongs to that larger format. The objective is not simply to remove black corners; the lens should maintain useful brightness and detail across the larger active area.

The Kyptec Automation® 25 MM 10 MegaPixel 1" Machine Vision Lens is a current example from the larger 1" family. Kyptec Automation® also currently publishes multiple 10 MP focal lengths within this 1" format range.

This lets a buyer using a larger camera sensor select the required focal-length geometry while remaining within a lens family designed around larger image coverage.

Why 1.1" Sensors Need Even More Care

High-resolution industrial cameras increasingly make sensor coverage especially important because the combination of larger sensor dimensions and small pixel sizes places demands on both image-circle diameter and optical resolution.

Kyptec Automation® currently provides a 25 MP Machine Vision Lens family published for 1.1" format, including 8 mm, 12 mm, 16 mm, 25 mm, 35 mm and 50 mm focal-length choices.

For example, the Kyptec Automation® 25 MM 25 MegaPixel 1.1" Machine Vision Lens is specifically published within that larger-format high-resolution family.

A buyer using a large high-resolution sensor should therefore consider both conditions simultaneously: can the lens cover the complete sensor, and can it preserve the fine optical detail the sensor is capable of sampling?

Can a Larger-Format Lens Be Used on a Smaller Sensor?

In many machine vision configurations, a lens designed for a larger image format can be used with a smaller compatible sensor because the smaller sensor captures only the central portion of the larger available image circle.

For example, a larger-format lens can potentially provide generous coverage on a smaller sensor, assuming mount, focal length, working distance and optical resolution are otherwise appropriate.

However, larger sensor coverage does not automatically mean the lens is the best choice for every smaller camera. Physical size, optical design, field of view, resolution requirement and budget still matter.

The important asymmetry is this: using a lens with more image-circle coverage than required is generally less risky from a vignetting standpoint than using a lens with less coverage than the sensor needs.

Can a 2/3" Lens Be Used on a 1" Sensor?

A 2/3" lens may physically mount to a 1" C-mount camera, but the larger sensor can extend beyond the image area for which the lens was designed.

The result can include corner darkening, peripheral softness, illumination falloff or outright vignetting. The severity depends on the specific optical design and active sensor dimensions, so it should not be assumed that every mismatch looks identical.

For a production system, choosing a lens intended for at least the camera's sensor format is the more reliable approach.

Kyptec Automation® makes this comparison straightforward because its live Machine Vision Lens portfolio includes both 2/3" 10 MP and 1" 10 MP lens families. A buyer can therefore maintain a comparable resolution class while moving to a lens format appropriate for the larger sensor.

Can a 1" Lens Be Used on a 1.1" Sensor?

The same compatibility principle applies. A 1.1" sensor requires more coverage than a smaller 1" format.

Even when the difference sounds modest, the sensor corners are the most demanding coverage points. If the lens image circle does not provide adequate margin, peripheral shading or image-quality loss can become visible.

For a camera built around a 1.1" active sensor, a lens explicitly designed for the corresponding larger coverage is therefore the safer purchasing choice.

Kyptec Automation® provides a dedicated 25 MP 1.1" Machine Vision Lens family for this class of high-resolution imaging.

Vignetting Can Reduce Defect Detection Reliability

Suppose a vision system inspects a broad component for small contamination spots. The central image area is bright and high contrast, but the corners are significantly darker because of inadequate lens coverage.

A dark contamination spot near the centre may be easy to detect. The same defect near the darkened corner may produce much weaker contrast against the local background.

The inspection algorithm can therefore develop position-dependent sensitivity. Raising exposure to brighten the corners can overexpose the centre. Lowering a threshold to catch corner defects can create additional false positives elsewhere.

This is why a machine vision lens for defect inspection should provide more than nominal sensor coverage. It should deliver usable image information across every region where a defect can occur.

Kyptec Automation® positions its Machine Vision Lens products around high-resolution industrial imaging, low distortion, consistent focus and reliable inspection performance.

Vignetting Can Also Affect OCR and Fine Features

Tiny text, date codes and fine printed features are particularly sensitive to peripheral optical performance because their character strokes occupy relatively few pixels.

If text moves toward a poorly covered sensor corner, reduced brightness and declining edge contrast can make character separation less reliable.

The problem can be misdiagnosed as an OCR software issue even though the fundamental cause lies in the lens-camera optical match.

Before tuning recognition thresholds, engineers should therefore check whether the same text is consistently sharp and illuminated at the centre and corners. If performance changes strongly with image position, lens coverage deserves investigation.

Sensor Coverage Affects Dimensional Measurement Too

Dimensional inspection depends on stable edge localisation throughout the measurement field.

If a lens is undersized for the sensor, the outer image can show stronger shading, softer edges or geometric degradation. This can cause measurement quality to vary according to where a feature lies within the image.

Software calibration can compensate for predictable distortion, but it cannot transform unusable optical corners into high-quality image data.

A correctly sized machine vision lens is therefore an important foundation for dimensional measurement when features extend across a substantial portion of the sensor.

Why Dark Corners Cannot Always Be Fixed by Increasing Exposure

Increasing camera exposure brightens the entire sensor. It does not selectively restore the missing rays that an undersized lens fails to deliver to the extreme corners.

If corner illumination is moderately lower, exposure can make those areas numerically brighter, but the centre brightens at the same time. The central region may then saturate before the corners reach the desired level.

More importantly, if the sensor extends outside the useful image circle, exposure cannot create image detail where the lens does not adequately project it.

The correct solution to a significant sensor-coverage mismatch is therefore optical: use a machine vision lens designed for the camera's sensor format.

Why Camera Gain Is Not a True Fix for Sensor-Coverage Problems

Digital or analog camera gain can also make a dark corner look brighter, but it amplifies the available signal and noise rather than correcting the optical cause.

If the corner receives much less light, raising gain increases noise in the same region. Fine inspection features can remain low contrast or become noisier.

A production machine should therefore avoid relying on aggressive gain compensation for a lens that is fundamentally undersized.

Correct image-circle matching provides a stronger foundation than trying to recover inadequate optical illumination electronically.

Flat-Field Correction Has Limits

Image-processing systems can sometimes apply flat-field or shading correction to compensate for gradual brightness variation across the sensor.

This can be useful when moderate illumination falloff exists in an otherwise well-designed optical system. It should not be treated as permission to ignore lens sensor coverage.

If the corners contain sharply reduced optical resolution, severe vignetting or no useful image at all, software correction cannot recreate missing spatial information.

For machine vision buying decisions, the lens should first provide adequate physical image coverage. Software correction should refine the system, not rescue an incorrect lens format.

Why Peripheral Sharpness Can Decline Before the Corners Turn Black

One of the more subtle consequences of using a lens too close to its coverage limit is that the image may not show obvious black corners, yet peripheral detail can still be weaker than central detail.

The outer sensor area corresponds to rays passing through the lens at greater field angles. If the lens is being asked to cover more sensor area than intended, peripheral aberrations and reduced contrast can become significant before hard mechanical vignetting appears.

This matters greatly in high-resolution inspection. A buyer may look at the complete image and conclude that coverage is acceptable because every corner contains visible scene information. A small defect or narrow edge in those corners may nevertheless be poorly reproduced.

For this reason, sensor coverage should be qualified with the smallest inspection feature, not just a white wall or large object.

Why Larger Sensors Place Greater Demands on Lens Design

A larger sensor reaches farther from the optical axis. The lens must therefore deliver useful imaging performance across a larger field angle and larger image circle.

This requires more than simply scaling the lens barrel. Optical correction for distortion, field curvature, astigmatism, illumination and resolution must remain controlled across the larger image area.

This explains why sensor format is an important machine vision lens specification independent of megapixel count.

The Kyptec Automation® 25 MP 1.1" Machine Vision Lens family is a good example of a portfolio built around both high resolution and larger sensor coverage. Current options include Kyptec Automation® 16 MM 25 MegaPixel 1.1" Machine Vision Lens, Kyptec Automation® 35 MM 25 MegaPixel 1.1" Machine Vision Lens and longer or shorter focal lengths in the same family.

Megapixels and Sensor Format Must Be Checked Separately

A 10 MP camera does not automatically require a lens labelled 10 MP, and a 10 MP lens is not automatically compatible with every 10 MP camera.

The camera may use a 2/3" sensor, 1" sensor or another physical format. Lens resolution and sensor coverage are therefore two separate checks.

Kyptec Automation® illustrates this clearly by publishing 10 MP Machine Vision Lens families in both 2/3" and 1" formats.

For example, a buyer can compare the Kyptec Automation® 25 MM 10 MegaPixel 2/3" Machine Vision Lens with the Kyptec Automation® 25 MM 10 MegaPixel 1" Machine Vision Lens. The focal length and broad resolution class are similar, but the published image-format requirement differs.

That is exactly the type of comparison an industrial buyer should make before ordering.

Why Focal Length Does Not Determine Image Circle

An 8 mm lens is not automatically designed for a smaller sensor than a 50 mm lens, and a 50 mm lens is not automatically suitable for a larger sensor.

Focal length controls field-of-view geometry. Image format describes sensor coverage.

Kyptec Automation® currently publishes an 8 mm lens in its 2/3" 5 MP family and also an 8 mm lens in its 1.1" 25 MP family. Similarly, it publishes 50 mm options across several format and resolution groups.

This demonstrates why buyers should never infer sensor coverage from focal length.

Aperture Does Not Change an Undersized Lens Into a Larger-Format Lens

Changing aperture can influence illumination falloff and image quality, but it does not fundamentally redesign the image circle for which the lens was constructed.

Stopping down may reduce some peripheral aberrations in certain optical configurations and can alter the appearance of shading, but a lens designed for a smaller sensor remains a smaller-format optical system.

If the sensor lies beyond the useful image-circle boundary, changing F number is not the correct primary solution.

This distinction prevents a common troubleshooting mistake where engineers spend time adjusting iris settings while the underlying lens-camera format mismatch remains unchanged.

How to Check Sensor Coverage Before Buying a Machine Vision Lens

The safest process begins with the camera datasheet.

Identify the actual sensor format or active sensor width and height. Do not rely only on megapixels. Then identify the image-format specification published for the candidate machine vision lens.

The lens format should meet or exceed the camera's required coverage.

Next, confirm the mechanical mount, focal length, optical resolution and required field of view. Sensor coverage alone does not guarantee that the lens will provide the correct imaging geometry.

For Kyptec Automation® products, the Machine Vision Lens collection provides a useful starting point because the current portfolio separates 2/3", 1" and 1.1" format options across different resolution and focal-length classes.

How to Check an Existing Camera-Lens Combination for Vignetting

If a system is already assembled, begin with a uniformly illuminated flat target.

Capture an image without automatic brightness correction if possible. Compare the centre brightness with the edges and corners. Look for gradual falloff as well as abrupt dark boundaries.

Then repeat the test using the smallest real inspection feature at several image positions. A coverage problem can be more obvious in defect or edge contrast than in overall brightness.

If the camera datasheet confirms a larger sensor format than the lens specification, that mismatch becomes a strong explanation for the observed peripheral weakness.

Do Not Judge Coverage From a Cropped Camera Preview

Some camera software displays only a region of interest or scaled preview. This can hide sensor-coverage problems.

If the preview uses only the central sensor region, an undersized lens can appear perfectly compatible because the problematic corners are excluded.

Coverage should therefore be checked using the complete active sensor image at full frame.

This is particularly important when commissioning a high-resolution camera whose full sensor may be larger than the previously used camera even though the software initially displays a similar preview window.

Camera Upgrades Often Reveal Previously Hidden Lens Problems

A common industrial scenario involves upgrading an existing camera while leaving the original lens in place.

The new camera may have more pixels, a larger sensor, or both. Because the mount remains C mount and the old lens physically fits, it is reused.

If the new sensor is physically larger than the previous one, the lens may no longer provide adequate image-circle coverage. Dark corners or peripheral softness can appear even though the old system worked correctly.

This is why every camera upgrade should trigger a complete Machine Vision Lens compatibility review.

The replacement lens should be selected according to the new sensor format, not merely the focal length used in the old system.

Why Cropping the Larger Sensor Is Usually a Compromise

Software cropping can remove dark corners by restricting the camera to a central region that the existing lens covers adequately.

This can be a temporary or application-specific solution, but it means the system no longer uses the complete sensor that was purchased. The effective field of view changes, and available pixel count may be reduced.

If the purpose of upgrading to the larger sensor was wider coverage or higher full-frame resolution, cropping undermines part of that benefit.

A properly sized machine vision lens normally provides a cleaner long-term solution when the full sensor is genuinely required.

Selecting Kyptec Automation® Machine Vision Lens Format by Camera Sensor

For a smaller-format industrial camera, a 2/3" Machine Vision Lens can provide an efficient optical match when the camera sensor is within that class and the focal-length and resolution requirements are satisfied. Kyptec Automation® currently provides multiple 5 MP and 10 MP 2/3" options across different focal lengths.

For a larger 1" camera sensor, Kyptec Automation® provides 10 MP 1" Machine Vision Lens choices, giving system integrators larger image-format coverage while retaining several focal-length options.

For larger high-resolution 1.1" camera requirements, the Kyptec Automation® 25 MP Machine Vision Lens family extends coverage and optical resolution together across several focal lengths.

This tiered structure is useful because a buyer can select according to actual camera format rather than trying to force one Machine Vision Lens family onto every sensor.

Why Kyptec Automation® Is Useful for Sensor-Coverage-Based Lens Selection

A specialised machine vision portfolio is valuable when sensor coverage, focal length and optical resolution can be considered together.

Kyptec Automation® currently offers Machine Vision Lens models across several image formats and focal lengths, including 2/3" 5 MP options, 2/3" and 1" 10 MP options, and larger 1.1" 25 MP models.

This gives OEMs, system integrators and machine builders a practical path for maintaining their required field-of-view geometry while choosing a lens designed for the sensor being used.

Instead of treating “C mount” as sufficient information, the buyer can evaluate mount + image format + focal length + resolution as one compatibility chain.

That is a much stronger approach for avoiding vignetting, dark corners and expensive camera-lens mismatches during commissioning.

Frequently Asked Questions About Machine Vision Lens Image Circle, Vignetting and Sensor Coverage

1. How do I know if my machine vision lens is too small for my camera sensor?

Start by comparing the image format specified for the lens with the active sensor format of the camera. If the camera sensor is physically larger than the lens's supported format, the lens may not provide sufficient image-circle coverage. Symptoms can include corner darkening, obvious vignetting, peripheral softness or black corners. Do not judge compatibility from C mount or focal length alone. Kyptec Automation® currently publishes distinct 2/3", 1" and 1.1" Machine Vision Lens families, which helps buyers match the lens format to the camera before installation.

2. Why are the corners of my machine vision image darker than the centre?

Corner darkening can come from several causes, including optical falloff, illumination non-uniformity, mechanical obstruction or insufficient lens image-circle coverage. If the lens is designed for a smaller sensor than the camera, the corners are especially likely to receive reduced usable light because they lie farthest from the optical centre. Compare the camera sensor format with the lens specification and test a uniformly illuminated target. If a smaller-format lens is installed on a larger sensor, moving to a correctly sized Kyptec Automation® Machine Vision Lens can address the root compatibility issue rather than compensating electronically.

3. Does vignetting always mean the lens is too small for the sensor?

No. Vignetting can also be caused by filters, adapters, mechanical apertures or illumination conditions. However, using a lens whose image format is smaller than the camera sensor is an important cause that should be checked early. If the camera uses a 1" sensor but the installed lens is rated only for 2/3", the format mismatch provides a strong reason to investigate sensor coverage. A correctly matched machine vision lens should be selected according to the camera's active sensor dimensions as well as its mount.

4. Can a 2/3" machine vision lens cover a 1" sensor?

It should not automatically be assumed to do so. A 1" sensor requires greater image-circle coverage than a 2/3" format. Although individual lens behaviour varies, using a smaller-format lens can produce vignetting or declining peripheral image quality. Kyptec Automation® currently provides both 2/3" and 1" 10 MP Machine Vision Lens families, allowing a buyer using a larger camera to choose optics explicitly intended for the larger format instead of relying on a smaller lens because the mount and focal length happen to match.

5. Can I use a 1" lens on a 2/3" camera sensor?

A lens designed for the larger format can often cover the smaller sensor because the smaller camera uses only the central portion of the available image circle. However, you must still confirm C-mount compatibility, focal length, field of view, resolution and physical fit. Using more image-circle coverage than necessary is generally less risky for vignetting than using too little coverage, but it does not eliminate the need for complete optical selection.

6. What is the difference between image circle and sensor format?

The image circle is the circular optical image projected by the lens. Sensor format is a practical classification describing the size class of the camera sensor or the sensor area a lens is designed to support. For compatibility, the useful image circle of the lens needs to cover the active rectangular sensor area. A Kyptec Automation® 2/3" Machine Vision Lens and a Kyptec Automation® 1.1" Machine Vision Lens therefore belong to different sensor-coverage classes even when they share the same focal length or C mount.

7. Why can the same focal length be available for several sensor formats?

Focal length and image-circle coverage perform different functions. Focal length determines imaging geometry and contributes to field of view, while sensor format indicates the image area the lens is designed to cover. Kyptec Automation® currently publishes 25 mm 10 MP Machine Vision Lenses in both 2/3" and 1" formats, demonstrating that the same nominal focal length can be built for different image-format requirements. Buyers should therefore match focal length and sensor coverage independently.

8. Can increasing the aperture remove dark corners caused by an undersized lens?

Changing aperture may alter the appearance of peripheral illumination, but it does not convert a smaller-format lens into one designed for a larger image circle. If the sensor extends beyond the lens's useful coverage, aperture adjustment cannot create the missing optical field. The more reliable solution is to choose a Machine Vision Lens intended for the camera's sensor format and then optimise aperture for brightness, depth of field and sharpness after the coverage issue has been resolved.

9. Can I fix lens vignetting in software?

Moderate brightness falloff can sometimes be corrected through flat-field or shading compensation, but software has limits. It cannot recreate high-resolution image information that the lens failed to project onto the outer sensor area, and it cannot restore completely black corners. If vignetting comes from a fundamental sensor-format mismatch, using a correctly sized machine vision lens is the stronger solution. Software correction should refine an appropriate optical system rather than compensate for a lens that is physically incapable of full sensor coverage.

10. Why did dark corners appear after upgrading my industrial camera?

The replacement camera may have a physically larger sensor than the original camera even if both use the same C-mount interface. The existing lens can therefore mount normally while failing to cover the new sensor. Check the active dimensions or format of the new camera and compare them with the old lens specification. If the new sensor is larger, select a Kyptec Automation® Machine Vision Lens whose image-format rating matches or exceeds the new requirement. Camera upgrades should always include a fresh lens-coverage check.

11. Does a higher megapixel machine vision lens automatically cover a larger sensor?

No. Optical resolution and sensor coverage are separate specifications. A high-megapixel lens can theoretically be designed for a smaller sensor, while a lower-resolution lens can be designed around a larger image format. Buyers should therefore look at both megapixel class and published lens format. Kyptec Automation® makes this distinction visible through its portfolio structure: the current range contains different resolution and format combinations rather than treating megapixel count as a substitute for sensor size.

12. Is a 1.1" Machine Vision Lens necessary for every 25 MP camera?

Not simply because the camera is 25 MP. You must identify the physical sensor size. If the camera uses a sensor that requires 1.1" image-format coverage, a lens designed for that format is appropriate. If the physical sensor is smaller, its exact requirements may differ. Kyptec Automation® currently provides a 25 MP 1.1" Machine Vision Lens family across several focal lengths specifically for larger-format high-resolution imaging, but the buyer should always match the actual camera sensor rather than selecting from megapixels alone.

13. Why are small defects harder to detect near dark image corners?

A small defect depends on local contrast and spatial detail. When the corner receives less light or the lens becomes optically softer there, the defect can produce a weaker image signal than the same defect at the centre. This creates uneven inspection sensitivity across the frame. Selecting a Machine Vision Lens with correct sensor coverage and validating minimum defects at the centre, edges and corners helps ensure that the complete active image is useful for inspection rather than only the central region.

14. How should I test whether a machine vision lens really covers the full sensor?

Capture a full-resolution image of a uniformly illuminated flat surface using the entire active sensor. Look for abrupt dark boundaries, progressive corner shading and asymmetry. Then place a fine real inspection target or minimum defect at several positions, including every corner, and compare sharpness and contrast. A lens should not be considered suitable merely because some image appears at the edge. The complete required sensor area should provide usable image quality for the actual inspection.

15. Should I choose a lens format exactly equal to the sensor size or larger?

The lens should provide coverage appropriate to the camera's active sensor, and a lens designed for a larger compatible image format can offer additional coverage margin. However, the final choice should still consider focal length, optical resolution, mechanical size and application geometry. Kyptec Automation® provides Machine Vision Lens families across different formats so buyers can select according to the actual camera rather than automatically oversizing every optical component.

16. Why does cropping the camera image remove vignetting but not solve the lens problem?

Cropping simply discards the outer pixels where the lens performs poorly. It does not increase the original image circle. This can be acceptable if the application genuinely needs only the central sensor region, but it reduces effective sensor usage and changes field of view. If the machine was purchased specifically to use the full large sensor, cropping sacrifices part of that benefit. A correctly sized Kyptec Automation® Machine Vision Lens allows the system to use the intended sensor area instead of hiding an optical mismatch.

17. What should I provide when asking for a Machine Vision Lens for a new industrial camera?

Provide the camera's exact sensor format or active width and height, horizontal and vertical resolution, pixel size if available, lens mount, required field of view, working distance and desired focal-length range. The physical sensor dimensions are essential because megapixel count alone does not define image-circle requirements. With these values, the Kyptec Automation® Machine Vision Lens collection can be narrowed to the appropriate 2/3", 1" or 1.1" coverage class before focal length and optical resolution are finalised.

18. What is the safest way to avoid buying a Machine Vision Lens that is too small for the sensor?

Treat sensor coverage as a mandatory first-stage compatibility check. Confirm the camera's active sensor size, then choose a lens whose published image format covers that sensor. Only after this should focal length, working distance, aperture and megapixel class be finalised. Do not rely on C mount, product photographs or focal length alone. Kyptec Automation® provides clearly separated Machine Vision Lens format families, including 2/3", 1" and 1.1" current options, making this compatibility-driven buying process easier for OEMs, machine builders and system integrators.

Final Guide: Match Image Circle to the Camera Before Optimising Anything Else

A machine vision lens that is too small for the camera sensor creates an optical limitation before inspection software even receives the image. The sensor reaches farther from the optical centre than the lens was designed to support, and the outer image can become progressively darker, softer or completely vignetted.

The problem begins with sensor coverage, not megapixels. A lens can have the correct C-mount thread and the correct 25 mm focal length while still being wrong for the camera because its image format is too small. Likewise, two 25 mm lenses can belong to different sensor-coverage classes even though their basic focal-length description appears identical.

The correct purchasing workflow should therefore begin with the camera sensor. Identify the physical sensor format or active width and height. Then select a machine vision lens whose image-format specification is appropriate for that active area. After coverage is confirmed, check focal length, working distance, optical resolution, aperture and installation geometry.

Kyptec Automation® provides a particularly practical structure for this process through its Machine Vision Lens portfolio. The current range includes 2/3" 5 MP lenses, 2/3" 10 MP lenses, larger 1" 10 MP options and a high-resolution 1.1" 25 MP family. This gives industrial buyers the flexibility to choose according to camera sensor size while retaining multiple focal-length options within the relevant coverage class.

For a compatible smaller-format camera, a product such as the Kyptec Automation® 16 MM 5 MegaPixel 2/3" Machine Vision Lens provides a current 2/3" option. For higher-resolution 2/3" requirements, the Kyptec Automation® 25 MM 10 MegaPixel 2/3" Machine Vision Lens represents another verified configuration.

Where the camera requires larger 1" coverage, the Kyptec Automation® 25 MM 10 MegaPixel 1" Machine Vision Lens provides the same broad focal-length class within a larger-format family. For demanding high-resolution cameras requiring 1.1" coverage, buyers can move into models such as the Kyptec Automation® 16 MM 25 MegaPixel 1.1" Machine Vision Lens, Kyptec Automation® 25 MM 25 MegaPixel 1.1" Machine Vision Lens, Kyptec Automation® 35 MM 25 MegaPixel 1.1" Machine Vision Lens and Kyptec Automation® 50 MM 25 MegaPixel 1.1" Machine Vision Lens.

The purpose is not to choose the physically largest lens available. The purpose is to select the correct optical coverage class for the sensor being used.

When the machine vision lens image circle properly covers the complete active sensor, the camera can use the sensor area for which it was selected, peripheral inspection becomes more consistent, dark corners and severe vignetting are avoided, and small features can be evaluated across a much larger percentage of the image.

That is why sensor coverage should be checked before the purchase order is placed, not after the camera is already mounted in the machine. Matching the Kyptec Automation® Machine Vision Lens format to the actual industrial camera sensor provides a stronger foundation for reliable inspection and prevents one of the most avoidable camera-lens compatibility mistakes in machine vision system design.