Lenses Archives - 1stVision Inc. - Machine Vision Articles

March 14, 2025March 14, 2025

Considerations in using an F-mount vs. a threaded mount

For machine vision purposes, we generally advise against using F-mount. We don’t have a dog in the hunt for leisure or artistic photography, but for reliability in many machine vision applications there are shortcomings with F-mounts.

EMERALD series F-mount lens – Courtesy Schneider Optics

Even our premier partner Schneider Optics, produces very fine F-mount lenses – the optics are first class! But just as a reliable auto dealership would counsel against buying a compact sedan to tow a heavy boat, we would hope to engage you in dialogue about your imaging application – and help you choose the best lens.

There are many lens mounts available

The wide range of lens mounts is, generally speaking, a very good thing. It permits camera designers and manufacturers to specialize in what they are good at; and likewise for lens designers and their own production facilities. The former is electronics while the latter is about optics.

By defining standards for lens mounts, we all benefit from market competition, which drives quality, feature, and price differentiation.

Some mounts are for large-format sensors. Some for small sensors. Some for “quick change”. Some for stability. Some can fit several niches. Some can in theory but shouldn’t be pushed in practice. Below we provide examples.

Lens families from a single manufacturer by sensor size and pixel size – Courtesy Schneider Optics

So what’s wrong with F-mounts?

If you are a sports photographer, there’s nothing wrong with F-mount. The bayonet mount design is ideal for quick lens changes, and the “money shot” may require a quick lens swap. If shooting at really short exposure times, inherent instability in the mount design may not have an impact on image quality.

While the F-mount name traces to the famous Nikon F camera series, one might also think of it as for “Fotographie” – the German work for photography – if you like mnemonic hints.

But for machine vision applications, one typically mates the lens to the camera “forever”, so quick-change benefits are of little value. And compared to screw mounts, for example, it’s clear that the bayonet mount, with just two securing points, might suffer in a high-vibration environment. Whether on the factory floor, a traffic camera gantry, or a moving vehicle, the lens and camera should act as one. Stability is key.

For the record, F-mount defines a standard Flange Distance of 46.5mm from the mounting surface of the camera to the sensor, as well as standardized mechanics on the size and position of the male pins on the lens and the female receptors on the camera body. For those cameras or lenses with electrical contacts as well, there are variances. But mechanically and optically and F-mount is an F-mount.

What about the M42 lens mount?

While the M42 lens mount came into existence for “photography”, when computers and then machine vision emerged, M42 has become one of many popular lens mounts. The threaded screw mount design provides a very secure connection that binds along several turns of the screw – so it’s very resistant to vibration.

But while the conceptual design is great, M42 isn’t really a “full standard” in two important ways…

M42 doesn’t define flange distance

Every lens must precisely focus light rays onto the sensor surface. Camera makers position sensors a precise distance from the shoulder of the mount, a distance referred to as the flange distance, or flange focal distance. Curiously, there isn’t universal agreement on what that distance should be – though there is some convergence on a couple of de facto conventions.

The M42 lenses may need to have an extension tube added so that they can image on a camera sensor. Thankfully an extension tube is an inexpensive but effective accessory – but it’s important to note focal distances and source components accordingly.

M42 doesn’t define thread pitch

The second caveat with M42 mounts is that there are at least two common thread pitches offered: both 0.75 and 1.0.

Annotated snapshot of 1stVision lens selector tool.

If we use the 1stVision lens-selector, the Lens Mount dropdown shows both M42x0.75 as well as M42x1 options (as well as many other lens mounts). So if you know the camera mount specifications, you can find lenses that will thread correctly – but one needs to pay attention!

All the mounts we offer

To the left is a snapshot from the 1stVision lens-selector, showing the dropdown for all lens mounts we offer. If one chooses “All” it yields some 200 lenses across more than 10 manufacturers.

By specifying the lens mount, for the camera you are considering, one need only select a couple of additional dropdowns like sensor format, and focal length, to home in on candidate lenses for your application.

Each mount has its role. While a camera designer sometimes has options relative to sensor size, intended market, and price : performance decisions, there are good reasons why each mount type exists. And while some cameras are available with two or more mount options, generally speaking the camera you choose will dictate the mount – and hence the lens options.

Don’t fixate on the mount

While we’ve discussed certain aspect of lens mounts in this blog, you can generally trust that camera designers have chosen a suitable one for any particular camera – after all they want to maximize the number of cameras they can sell. There are many other considerations in machine vision lens selection. You can read all about it, or just…

1st Vision’s sales engineers have over 100 years of combined experience to assist in your camera and components selection. With a large portfolio of cameras, lenses, cables, NIC cards and industrial computers, we can provide a full vision solution!

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February 13, 2025February 13, 2025

Moritex ML-M-HR 2/3″ Format Lenses

Superior vibration resistance and mechanical design

Two of six available ML-M-HR lens models – Courtesy Moritex

Value Engineering

Every field with diverse product offerings has its own broad mix from which to choose. Some offerings are generalized; some fit a specific niche. When designing a machine vision application, and choosing components like cameras, sensors, lenses, lighting, etc., each component has to be at least slightly better than “good enough”, but need not be more than needed. The whole field of value engineering has evolved to guide practitioners in achieving required functionality while also respecting budgetary goals.

Larger FA series design goals which ML-M-HR series share- Courtesy Moritex

Moritex ML-M-HR lens series

The Moritex ML-M-HR series is part of Moritex larger FA Series of lenses. The “FA” stands for Factory Automation, which suggests points including:

Robust mechanical engineering
Quality designed to deliver reliable results and stand the test of time
Priced to permit volume purchases by achieving return on investment

Of course, the lenses are not constrained to factory automation, and you may purchase as few as you need. The factory automation insight just helps to understand their design heritage and largest market.

Specifics:

Key attributes of the Moritex ML-M-HR lens series

Pixel size and resolving capacity

Designed for 4.5 µm pixels, the lenses may of course also be used with larger pixels, but aren’t suitable for smaller. So they are an ideal fit for Sony Pregius 3rd generation sensors.

See Moritex lens families for other pixel sizes and lens types. The Moritex ML-M-HR lenses resolve to 130 line pairs / mm. See our Knowledge Base article Key Considerations in Machine Vision Lens Selection for generalized guidance on concepts.

With wide-range anti-reflective (AR) coatings, the lenses provide consistent transmission from visible (Vis) through near infrared (NIR) wavelengths, i.e. 400 ~ 1100nm.

Six member family

There are six choices in the Moritex ML-M-HR series, spanning from focal lengths 8mm – 50mm, at typical intervals. The link in the previous sentence takes you to the detailed table – and quote request buttons.

Robotics application is just an example – Courtesy Moritex

January 20, 2025January 22, 2025

Explained: Trifecta of lens f-stop, wavelength and Airy disc

In this blog we tackle a set of issues well-known to experts. It’s complex enough to be non-obvious, but easy enough to understand through this short tutorial. And better to learn via a no-cost article rather than through trial and error.

Alternative to reading on, let us help you get the optics right for your application. Or read on and then let us help you anyway. Helping machine vision customers choose optimal components is what we do. We’ve staked our reputation on it.

Click here for help from 1stVision

Aperture size and F-stop

Most understand that the F-stop on a lens specifies the size of the aperture. Follow that last link to reveal the arithmetic calculations, if you like, but the key thing to keep in mind at the practical level is that F-stop values are inversely correlated with the size of the aperture. So a large F-number like f/8 indicates a narrow aperture, while a small F-number like f/1.4 corresponds to a large aperture. Some lens designs span a wider range of F-numbers than others, but the inverse correlation always applied.

Iris controls the aperture – Courtesy Edmund Optics

Maximizing contrast might seem to suggest a large aperture

For machine vision it’s always important to maximize contrast. The target object can only be discerned when it is sufficiently contrasted against the background or other objects. Effective lighting and lensing is crucial, in addition to a camera sensor that’s up to the task.

“Maximizing light” (without over-saturating) is often a challenge, unless one adds artificial light. That would tend to suggest using a large aperture to let more light pass while still keeping exposure time short enough to “freeze” motion or maximize frames per second.

So for the moment, let’s hold that thought that a large aperture sounds promising. Spoiler alert: we’ll soften our position on this point in light of forthcoming points.

Depth of Field – DoF

While a large aperture seems attractive so far, one argument against that is depth of field (DoF). In particular, the narrowest effective aperture maximizes depth of field, while the largest aperture minimizes DoF.

Correlation of aperture size and depth of field – Courtesy Edmund Optics

Depending on the lens design, the difference in DoF between largest vs. smallest aperture may vary from as little as a few millimeters to as great as many centimeters. Your applications knowledge will inform you how much wiggle room you’ve got on DoF.

So what’s the sweet spot for aperture?

Barring further arguments to the contrary, the largest aperture that still provides sufficient depth of field is a good rule of thumb.

Where do diffraction limits and the Airy disc come into it?

Optics is a branch of physics. And just like absolute zero in the realm of temperature, Boyle’s law with respect to gases, etc., there are certain constraints and limits that apply to optics.

Whenever light passes through an aperture, diffraction occurs – the bending of waves around the edge of the aperture. The pattern from a ray of light that falls upon the sensor takes the form of a bright circular area surrounded by a series of weakening concentric rings. This is called the Airy disk. Without going into the math, the Airy disk is the smallest point to which a beam of light can be focused.

And while stopping down the aperture increases the DoF, our stated goal, it has the negative impact of increasing diffraction.

Correlation of aperture to diffraction pattern – Courtesy Edmund Optics

Diffraction limits

As focused patterns, containing details in your application that you want to discern, near each other, they start to overlap. This creates interference, which in turn reduces contrast.

Every lens, no matter how well it is designed and manufactured, has a diffraction limit, the maximum resolving power of the lens – expressed in line pairs per millimeter. There is no point generating an Airy disk pattern from adjacent real-world features that are larger than the sensor’s pixels, or the all-important contrast needed will not be achieved.

And wavelength’s a factor too?

Indeed wavelength is also a contributor to contrast and the Airy disc. As beings who see, we tend to default to thinking of light as white light or daylight, which is a composite segment of the spectrum, from indigo, blue, green, yellow, orange, and red. That’s from about 380 nm to 780 nm. Below 380 nm we find ultraviolet light (UV) in the next segment of the spectrum. Above 780 nm the next segment is infrared (IR).

Monochrome light better than white light

An additional topic relative to the Airy disc is that monochrome light is better than white light. When light passes through a lens, it refracts (bends) differently in correlation with the wavelength. This is referred to as chromatic aberration.

Transverse and longitudinal chromatic aberration – Courtesy Edmund Optics

If a given point on your imaged object reflect or emits light in two more more of the wavelengths, the focal point of one might land in a different sensor pixel than the other, creating blur and confusion on how to resolve the point.

An easy way to completely overcome chromatic aberration is to use a single monochromatic wavelength! If your target object reflects or emits a given wavelength, to which your sensor is responsive, the lens will refract the light from a given point very precisely, with no wavelength-induced shifts.

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The moral of the story

The takeaway point is that the trifecta of aperture (F-stop) and wavelength each have a bearing on the Airy disc, and that one wants to choose and configure the optics and lighting to optimize the Airy disc. This leads to effective applications performance – a must have. But it can also lead to cost-savings, as lower cost lenses, lighting, and sensors, optimally configured, may perform better than higher cost components chosen without sufficient understanding of these principles.

January 20, 2025

EO HPI + Fixed Focal Length Lenses

HPI+ Fixed Focal Length Lenses – Courtesy Edmund Optics

Front-loading the article by unpacking the acronyms:

EO = Edmund Optics, longstanding innovators in machine vision lensing

HP = High Performance

I = Denotes “instrumentation” – Streamlined mechanical designs and fixed apertures

+ = Targeted for larger 4^th gen SONY Pregius sensors: 24.5MP 1.2” IMX530 and IMX540 sensors

Fixed Focal Length Lenses… ok no acronym to unpack there… but worth noting that fixed focal length lenses, with fewer moving parts, offer high performance with lower manufacturing costs. Which translates to a compelling value proposition.

With 18 members in the EO HPI+ Fixed Focal Length Lens family, it’s possible to get the optimal fit in focal length and F-stop. These industrial lenses are built for exceptional performance in demanding factory automation (FA) and machine vision environments. The locking focus and iris rings prevent accidental adjustments.

SONY Pregious sensors – once more with feeling

While not the only player in the sensor space, SONY remains one of the most innovative and respected manufacturers. They regularly succeed their own prior releases through incremental and disruptive innovation. As we write this, there are four generations of SONY Pregious sensors. The 4th generation Pregius S captures up to 4x as much light as Sony’s own highly-praised 2nd generation Pregius from just a few years ago!

*Surface- vs back-illuminated image sensors – courtesy SONY Semiconductor Solutions Corporation*

24.5MP 1.2” SONY IMX530 and SONY IMX540

Consider the SONY IMX540 sensor for a moment. It’s designed in to at least 17 different camera models carried by 1stVision, across three different camera maufacturers: Allied Vision, IDS Imaging, and JAI.

First few rows of 1stVision’s camera offerings using Sony IMX540 sensor

At almost 25MP, with 2.74µm square pixels, yet only a 1.2″ diagonal size, it’s suited to the C-mount lens format. That’s a robust mount design that’s widely popular in machine vision, so adopters of cameras with this sensor and mount have a wide range of lenses from which to choose. That in turn offers a range of choices along the price : performance spectrum.

EO HPI+ FFL Lens Performance

Machine vision pros know that lens performance is often characterized by the optical transfer function, also called the modulation transfer function. The shape and position of the curve says a lot about lens quality and performance. It’s also useful when comparing lenses from different manufacturers – or even lenses from different product families by the same manufacturer.

Here’s the MTF curve for one of the Edmund Optics lenses:

25mm, f/2.8: Identical to 29-278 – Courtesy Edmund Optics

That’s just a representative example. We’ve got the MTF curves for each lens… either on our website datasheets or on request.