Machine Vision Lens for Different Product Sizes on the Same Production Line: How to Select FOV for Frequent Changeovers

A production line that handles only one product size is relatively straightforward from an optical-design perspective. The required field of view can be calculated around one object, the camera can remain at one fixed working distance, and the machine vision lens can be selected so that the product occupies an efficient portion of the sensor. The problem becomes more complicated when the same inspection station must handle several product sizes. A line may inspect a 40 mm component in one production batch, a 75 mm version after the next changeover and a 120 mm product later in the day. The machine builder must then decide whether one machine vision lens for multiple product sizes can provide sufficient FOV for every variant without sacrificing too much resolution on the smallest part.

Frequent changeovers create a fundamental optical trade-off. Designing the field of view around the largest product ensures that every variant fits inside the image, but smaller products then occupy fewer pixels. Selecting a tighter FOV around the smallest product improves image sampling but can crop larger products. Changing the camera position, refocusing the lens or replacing the machine vision lens during every changeover introduces additional setup complexity and can alter magnification, calibration and inspection repeatability. The best solution therefore depends on product-size range, smallest required defect, sensor resolution, working distance and how much mechanical adjustment the production process can realistically tolerate.

Kyptec Automation® offers a broad Machine Vision Lens portfolio containing multiple focal lengths across different sensor formats and optical resolution classes. The current portfolio includes 5 MP, 10 MP and 25 MP machine vision lens options as well as 2/3", 1" and larger-format configurations, enabling OEM machine builders and system integrators to design flexible inspection systems around the real range of product dimensions rather than forcing one optical configuration into every application.

Why Different Product Sizes Create a Machine Vision Lens Selection Problem

The field of view determines how much physical area the camera can see. If every product on the line must remain completely visible, the FOV must be large enough to accommodate the largest product plus any required positioning margin.

This sounds simple until the smallest product is considered.

Suppose the largest product is 150 mm wide while the smallest is only 50 mm. If the horizontal FOV is approximately 170 mm to accommodate the largest product and conveyor-position tolerance, the 50 mm product uses less than one-third of the available physical field. A large portion of the sensor then records surrounding background instead of useful product detail.

For applications such as presence detection this may be perfectly acceptable. For small-defect inspection across different product sizes, it can become a serious limitation because the smallest product receives fewer pixels per millimetre than it would with a tighter field.

Start With the Largest Product, but Do Not Stop There

The largest product normally establishes the minimum FOV required to avoid cropping. The machine vision lens should provide enough horizontal and vertical coverage for that product at the selected working distance.

However, choosing a lens only from this largest dimension is incomplete.

The smallest product should then be evaluated using the same FOV. Engineers need to determine how many pixels represent the minimum feature, defect, edge, gap or character that must still be inspected.

If the smallest feature remains sufficiently sampled, one fixed lens can potentially support the complete product family. If it does not, the system needs a different optical strategy.

Add Product Position Tolerance to the Required FOV

The FOV should normally be larger than the nominal dimensions of the largest product.

Products travelling on a conveyor can shift laterally, rotate slightly or arrive with normal mechanical positioning variation. If the lens is selected so that the largest product just touches the image boundaries under perfect positioning, normal production movement can push required features outside the frame.

A practical machine vision FOV for multiple product sizes should therefore include the largest object plus sufficient horizontal and vertical margin for expected positional variation.

Excessive margin, however, reduces pixels per millimetre. The goal is controlled margin, not the widest field possible.

Why the Smallest Product Can Determine Whether One Lens Is Practical

The largest object defines coverage, but the smallest object often defines usable resolution.

Imagine a 4,000-pixel-wide camera observing a 200 mm horizontal FOV. The average sampling is approximately 20 pixels per millimetre. A 100 mm product occupies roughly 2,000 horizontal pixels, while a 25 mm product occupies only about 500.

If both products need inspection of a 0.2 mm feature, that feature is represented by approximately four pixels under this simplified example regardless of product width because the FOV remains fixed. The relevant question is therefore whether this pixel scale provides enough information for reliable inspection.

If not, simply allowing the smaller product to occupy more of the image through software cannot create additional optical detail. The physical FOV or sensor resolution must change.

Calculate Pixels per Millimetre for the Fixed FOV

One of the most useful calculations for flexible production is:

Pixels per millimetre = sensor pixels across the measurement direction ÷ physical FOV in millimetres

If a camera provides 4,096 horizontal pixels over a 160 mm FOV, the system provides approximately 25.6 pixels/mm.

A 0.5 mm feature is therefore represented by approximately 12.8 pixels in the horizontal direction, assuming the feature aligns with that axis and ignoring other optical limitations.

This calculation should be performed for the largest required field before approving one lens for all product variants.

The buyer should ask not merely “Which focal length covers all my products?” but “Does that focal length leave enough pixels per millimetre for the smallest feature on every product?”

One Fixed Machine Vision Lens Can Be the Best Solution When the Size Range Is Moderate

If the largest and smallest products are not dramatically different in size and the camera has enough resolution, one fixed machine vision lens can provide the simplest and most repeatable solution.

The camera remains in the same mechanical position. Focus and aperture remain unchanged. Calibration can remain associated with one optical geometry, and product changeover is performed primarily through the inspection program rather than manual optical adjustment.

For many OEM systems, this reduces changeover time and decreases the risk that one operator focuses or repositions the camera differently from another.

The key requirement is that the FOV selected for the largest product still provides sufficient object sampling for the smallest inspection feature.

Why a 16 MM Machine Vision Lens Can Be Useful for Broader Multi-Product FOV

When the machine must accommodate relatively large products or substantial size variation, a moderate shorter focal length can provide the wider FOV required at a practical working distance.

For compatible 2/3" cameras, the Kyptec Automation® KL-1226 16 MM Machine Vision Lens With 10 MegaPixel & 2/3" Format Lens provides a 16 mm focal length, 10 MP optical resolution, C-mount interface, 2/3" image format and F2.8–16 aperture range.

A configuration such as this can be evaluated when the largest product requires relatively broad coverage. The final decision should then be verified against the minimum defect or feature on the smallest product rather than selected only because the widest product fits inside the image.

When a 25 MM Lens Can Provide a Better Compromise

A 25 mm focal length provides a tighter field than 16 mm under comparable sensor and working-distance conditions. This can be useful when the complete product-size family still fits within the narrower FOV.

The Kyptec Automation® KL-1228 25 MM Machine Vision Lens With 10 MegaPixel & 2/3" Format Lens provides a 25 mm, 10 MP, C-mount configuration for 2/3" sensors with an F2.8–16 aperture range.

For a flexible production line, this type of focal length can offer a useful balance: enough physical field for larger variants while allocating more of the sensor to the product than a much wider view.

The correct comparison is therefore not “16 mm versus 25 mm” in isolation. It is required FOV versus smallest inspection feature at the planned working distance.

Product Size and Product Height Are Different Problems

A frequent mistake is to treat changes in width or length as equivalent to changes in object height.

If product variants differ only in planar dimensions while their inspected surface remains at approximately the same height, one fixed focus setting may be practical.

If larger products are also taller or shorter, the object distance changes. This creates additional depth-of-field requirements and may alter magnification.

The lens-selection process should therefore document the minimum and maximum product height separately from horizontal and vertical dimensions.

A multi-product inspection system that covers every width but loses focus when a taller product enters the station is not genuinely changeover-ready.

Depth of Field Can Eliminate the Need to Refocus During Changeovers

Where product height varies moderately, sufficient depth of field can allow all variants to remain acceptably sharp without changing focus.

This is generally preferable to manually refocusing the machine vision lens every time the production line changes product because focus adjustment can alter the optical state and potentially require calibration verification.

Aperture can be adjusted during system development to obtain the depth-of-field range required for the highest and lowest product surfaces. The final production setting should then remain controlled.

The correct aperture must still preserve sufficient fine-detail performance and illumination; maximum depth of field should not be pursued without regard to resolution.

Why Frequent Refocusing Can Reduce Changeover Repeatability

A line that requires an operator to refocus the lens for every product size introduces a new source of variation.

Two operators may not choose exactly the same focus position. Even the same operator may produce slightly different results from one shift to another.

If the application performs measurement, defect sizing or position detection, changes in focus can also affect effective magnification and the pixel-to-world relationship.

For high-frequency product changeovers, the stronger design is therefore usually to create a fixed optical setup whenever the required product range and depth of field allow it.

Camera Repositioning During Every Changeover Should Be Avoided Where Possible

Moving the camera closer for a small product and farther away for a large one can maintain efficient sensor usage, but it also changes FOV and magnification.

The system may then require mechanical position verification and a different calibration state for every product variant.

This can be acceptable in an engineered recipe-based platform, but it increases complexity considerably compared with a fixed camera-lens geometry.

For OEMs selling machines into production environments where rapid product changeover matters, one mechanically fixed optical configuration often creates a more robust operating process.

Use the Largest Necessary FOV, Not the Largest Possible FOV

A wider FOV is not automatically more flexible.

If the largest product requires 140 mm of horizontal coverage including tolerance, designing the system for 250 mm simply because the lens can provide it wastes image resolution.

Those extra 110 mm consume sensor pixels without providing inspection value.

For machine vision lens selection for mixed product sizes, the ideal FOV is large enough for the largest valid product and its position tolerance, but no substantially larger than necessary.

This preserves as much sampling density as possible for smaller products.

Determine Whether Software ROI Is Enough for Smaller Products

When the physical FOV remains fixed, a software region of interest can isolate the smaller product and simplify processing.

This can make the image easier to analyze and reduce unnecessary background data, but it does not change optical magnification.

Cropping a 500-pixel-wide small product from a 4,000-pixel image does not turn it into a 2,000-pixel product. The underlying spatial sampling remains exactly the same.

Software ROI is therefore useful for processing efficiency and product-specific algorithms, but it cannot substitute for sufficient lens-camera resolution.

Different Product Recipes Can Share One Optical Configuration

A well-designed flexible inspection station can keep one camera position, machine vision lens, aperture and focus setting while loading different inspection recipes for different product variants.

Each recipe can define expected object size, search regions, defect criteria and measurement limits while the optical geometry remains fixed.

This is often one of the most practical strategies for machine vision inspection with frequent product changeovers because optical repeatability is preserved even as software requirements change.

The lens becomes a stable hardware foundation for the entire product family.

Larger Sensors Can Help Combine Wide FOV With Better Sampling

When the largest product requires a wide physical field but the smallest defect still needs substantial pixel coverage, a higher-resolution larger-format system may provide a more effective solution than continuously narrowing the FOV.

Kyptec Automation® includes larger-format high-resolution machine vision lens options such as the Kyptec Automation® KL-1240 25 MM Machine Vision Lens With 25 MegaPixel & 1.1" Format Lens. The official product page identifies the model as a 25 mm, 25 MP C-mount machine vision lens with an F2.8–22 aperture range; it is published within the larger-format 25 MP lens family.

A configuration of this class can be valuable when one camera must cover a comparatively large product while preserving significantly more total image sampling for fine inspection.

Why Sensor Format Must Be Considered With Focal Length

The same focal length does not produce the same field of view on every sensor format.

A 25 mm machine vision lens on a 2/3" camera and a 25 mm machine vision lens on a larger-format camera represent different complete imaging configurations.

This means an OEM should never standardize a flexible production system using only “25 mm focal length” as the optical requirement.

Sensor format, focal length, working distance and required FOV must be defined together.

Kyptec Automation® provides distinct product families for multiple sensor formats within its Machine Vision Lens collection, supporting this type of sensor-specific optical selection.

A 35 MM Lens Can Be Useful When the Product Family Is More Localized

Some flexible lines handle several product sizes, but all variants are still relatively small compared with the available working distance. In these cases, a longer focal length can provide a tighter FOV and stronger use of sensor pixels.

For compatible 1" systems, the Kyptec Automation® KL-1218 35 MM Machine Vision Lens With 10 MegaPixel & 1" Format Lens provides a 35 mm focal length, 10 MP resolution, 1" image format, C-mount and F1.4–16 aperture range.

This type of longer focal-length configuration can be evaluated when all product variants fit within a relatively localized field and the goal is to allocate more image area to the inspected object.

Decide Whether One Lens or Multiple Fixed Optical Stations Are More Practical

Not every product-size range should be forced into one inspection station.

If the largest product is many times larger than the smallest and both require detection of extremely small features, one fixed FOV may become inefficient.

In these cases, the engineering decision may involve creating separate optical recipes with controlled mechanical positions or even separate inspection stations.

The correct objective is not to minimize the number of lenses at all costs. It is to produce reliable inspection while maintaining acceptable changeover complexity.

A single fixed Kyptec Automation® machine vision lens is highly attractive when it satisfies both coverage and resolution requirements, but optical compromises should remain within the application's actual tolerance.

Product Changeover Validation Should Use the Extreme Variants

A flexible production system should be qualified with at least the largest and smallest products, not only the mid-size version.

The largest product confirms that the FOV and positional margin are adequate. The smallest product provides the most useful check of effective product sampling and minimum-feature visibility.

The tallest and shortest variants should also be included when product height differs.

Once these extremes meet the inspection requirement, intermediate variants become much easier to validate.

Keep the Lens Configuration Fixed After Qualification

After the correct field, focus and aperture are established, the optical settings should be treated as controlled production parameters.

If operators can freely adjust focus or camera position during every changeover, the advantages of selecting one common machine vision lens are largely lost.

OEMs can improve repeatability by documenting working distance, lens model, aperture, focus reference and acceptable FOV, then verifying these conditions during maintenance rather than altering them during normal product selection.

Why Kyptec Automation® Is a Practical Choice for Multi-Product Production Lines

Flexible manufacturing benefits from having several focal lengths and sensor formats available within one machine vision lens portfolio. Kyptec Automation® provides multiple options across 5 MP, 10 MP and 25 MP optical classes, with current focal lengths ranging from wide-field options through 50 mm configurations depending on the lens family.

For compatible 2/3" 10 MP systems, Kyptec Automation® KL-1226 16 MM Machine Vision Lens With 10 MegaPixel & 2/3" Format Lens can be evaluated where the largest product requires broader coverage, while Kyptec Automation® KL-1228 25 MM Machine Vision Lens With 10 MegaPixel & 2/3" Format Lens provides a tighter alternative where the product-size range permits it. Both official product pages specify 10 MP, C-mount, 2/3" configurations with F2.8–16 aperture ranges.

For larger sensor requirements, Kyptec Automation® KL-1218 35 MM Machine Vision Lens With 10 MegaPixel & 1" Format Lens offers a 35 mm, 10 MP, 1" C-mount configuration, while Kyptec Automation® KL-1240 25 MM Machine Vision Lens With 25 MegaPixel & 1.1" Format Lens provides a high-resolution larger-format option for applications where a wide physical inspection area must still preserve substantial image sampling.

This range allows OEM machine builders to choose one qualified Kyptec Automation® lens for a complete product family where practical, while still having alternative focal lengths and resolution classes available when another machine variant requires a different FOV.

Frequently Asked Questions About Machine Vision Lenses for Different Product Sizes and Frequent Changeovers

1. Can one machine vision lens inspect several different product sizes?

Yes, provided the lens gives enough FOV for the largest product and enough pixels per millimetre for the smallest required feature across all variants. A fixed lens is often preferable for frequent changeovers because it keeps working distance, focus and calibration more stable. The decision should therefore be based on both maximum product dimensions and minimum inspection detail.

2. Should I select machine vision FOV from the largest product size?

The largest product establishes the minimum field needed for complete coverage, but FOV should also include expected position tolerance. After that, verify the smallest product and smallest defect using the resulting pixels-per-millimetre scale. If fine features are under-sampled, the system may need higher total resolution or a different optical strategy.

3. How much extra FOV should I allow for product movement?

There is no universal percentage because it depends on conveyor guidance, fixture accuracy and allowable rotation. Measure the real maximum displacement and add enough margin to keep all inspection-critical features visible. Avoid excessive unused FOV because every unnecessary millimetre reduces the available pixels per millimetre.

4. Is a wider-angle machine vision lens always better for multiple product sizes?

No. A wider field makes it easier to fit large products but reduces object sampling for the same sensor resolution. The correct machine vision lens should provide only the amount of coverage required for the largest valid product and its positional tolerance while preserving enough resolution for the smallest feature.

5. How do I know whether the smallest product will still have enough resolution?

Calculate pixels per millimetre from camera pixels divided by physical FOV, then multiply that value by the smallest feature dimension. This gives an approximate number of pixels representing the feature. Final detectability should then be tested using real samples because optical sharpness and feature contrast also affect performance.

6. Is 16 mm or 25 mm better for a production line with different product sizes?

It depends on the required field. For compatible 2/3" 10 MP systems, Kyptec Automation® KL-1226 16 MM Machine Vision Lens With 10 MegaPixel & 2/3" Format Lens provides a wider optical option, while Kyptec Automation® KL-1228 25 MM Machine Vision Lens With 10 MegaPixel & 2/3" Format Lens provides a tighter alternative. The better choice is whichever covers the largest product while maintaining the required sampling.

7. Should I refocus the lens every time the product size changes?

Not if all product surfaces remain within the qualified depth of field. Keeping one fixed focus condition normally provides better changeover repeatability. If product heights differ enough to require refocusing, measurement scale and calibration should be verified for each approved optical state rather than assuming the original setup remains identical.

8. Can software zoom compensate for a small product inside a large FOV?

Software can crop or enlarge the displayed image, but it cannot create additional optical resolution. If the small product occupies only 500 actual sensor pixels, enlarging those pixels on-screen does not give it the information content of a 2,000-pixel image. The physical FOV and total sensor resolution determine real object sampling.

9. How can I reduce product changeover time in a machine vision inspection station?

Use a fixed camera position, machine vision lens, focus and aperture wherever the product family permits it. Then use product-specific software recipes for expected dimensions and inspection regions. This removes repeated optical adjustment from the normal changeover process and improves consistency between operators.

10. Does product height matter if only width and length are changing?

Yes if height varies between products. Changes in object distance affect focus and can also change magnification. A multi-product lens setup should therefore define minimum and maximum inspection-plane height as well as horizontal and vertical dimensions.

11. Would a larger sensor help when I need to inspect both large and small products?

Potentially. A larger high-resolution sensor can provide more total pixels across a broad FOV, allowing the largest product to fit while preserving greater sampling for fine features. A compatible high-resolution option such as Kyptec Automation® KL-1240 25 MM Machine Vision Lens With 25 MegaPixel & 1.1" Format Lens can be evaluated where this larger-format architecture matches the application.

12. When should I use a longer focal length for multi-product inspection?

A longer focal length can be useful when every product variant fits inside a relatively small field and the system benefits from allocating more sensor area to the object. For compatible 1" 10 MP systems, Kyptec Automation® KL-1218 35 MM Machine Vision Lens With 10 MegaPixel & 1" Format Lens provides a 35 mm option. Final selection must still be calculated from sensor size, working distance and required FOV.

13. Can one calibration be used for every product size?

Potentially, if the camera, lens, working distance, focus and inspection plane remain unchanged and the application uses the same geometric relationship. If different products require different camera positions, focus settings or inspection heights, calibration should be validated for each configuration. A fixed optical arrangement therefore simplifies flexible production considerably.

14. What happens if the FOV is much larger than the biggest product?

The system records unnecessary surrounding area and therefore uses fewer pixels per millimetre on the product than it could with a tighter field. This can reduce the available sampling for small defects or measurement features. Additional FOV is useful only when it supports real positioning or product-size requirements.

15. How should I qualify a machine vision lens for frequent production changeovers?

Test the largest product for complete coverage and position tolerance, then test the smallest product for minimum-feature detectability. Also validate the tallest and shortest products where height varies. Run the complete product family using the final focus, aperture and working distance before locking the optical configuration for production.

16. What information should I provide before buying one machine vision lens for multiple product sizes?

Provide the minimum and maximum product width, height and length, camera sensor format and resolution, available working distance, permitted product-position variation, smallest defect or feature, and whether product height changes between variants. These parameters allow the FOV and focal length to be chosen according to both largest-product coverage and smallest-feature resolution.

17. Where can I compare Kyptec Automation® lenses for flexible multi-product inspection?

The Kyptec Automation® Machine Vision Lens collection includes multiple focal lengths across different sensor formats and optical resolution classes, including 5 MP, 10 MP and 25 MP options. Buyers can first determine the maximum required FOV and minimum pixels-per-millimetre requirement, then compare suitable Kyptec Automation® machine vision lens configurations according to the camera format and planned working distance.

Select the FOV Around Both the Largest Product and the Smallest Feature

Designing a machine vision system for different product sizes is not simply a matter of choosing a lens wide enough to see everything. The largest product determines how much physical area must fit inside the image, but the smallest inspection feature determines whether that field is still useful. A very wide FOV may simplify product coverage while simultaneously reducing pixels per millimetre to a level where fine defects, narrow gaps, small characters or precise edges are no longer represented adequately.

The strongest approach is to establish the dimensions and positional tolerance of the largest product first and calculate the minimum required FOV. The resulting pixel scale should then be tested against the smallest feature on every product variant. Product-height variation should be evaluated separately to determine whether one fixed focus setting provides sufficient depth of field. If those requirements can be satisfied with one camera position and machine vision lens, the optical configuration can remain fixed while software recipes handle normal product changeovers.

Kyptec Automation® provides a comprehensive Machine Vision Lens portfolio spanning several focal lengths, sensor formats and resolution categories, giving OEM machine builders and system integrators the flexibility to select optics around real multi-product production requirements. By matching the appropriate Kyptec Automation® machine vision lens to the largest required FOV, smallest inspection feature, sensor resolution, working distance and product-height range, a flexible production line can achieve faster changeovers without unnecessarily sacrificing image detail, calibration stability or inspection repeatability.