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Views: 0 Author: Site Editor Publish Time: 2025-07-28 Origin: Site
People check the MTF of a lens by taking pictures of special charts, a process known as Lens MTF Testing. They use careful software to analyze these images. Lens MTF Testing tells us how well a lens preserves detail and contrast at different sizes. This information helps people determine if a lens will produce sharp and high-quality photos. Engineers and designers rely on Lens MTF Testing to select the best lens for specific tasks. MTF curves from Lens MTF Testing show how lenses and sensors interact, providing a complete understanding of system performance. Studies indicate that Lens MTF Testing reveals lens quality more effectively than simply checking resolution, as it examines contrast at various levels, which aligns with what people perceive as good image quality. Lens MTF Testing assists companies in developing better lenses and helps photographers choose the right lens for their needs. The process of Lens MTF Testing involves clear steps, precise setup, specialized tools, and thorough verification, ensuring that both hobbyists and professionals can trust the results.
MTF tells us how well a lens keeps detail and contrast. This helps you pick sharp and good lenses.
Good MTF testing needs a careful setup. Lenses must be clean. Lighting should be even. The camera must stay steady and straight.
Using slanted-edge charts and the right software helps MTF testing. It makes the process faster and more correct.
Take many photos with the same settings. Look at the data closely. This helps you get results you can trust.
Reading MTF charts shows you how sharp a lens is. This helps you choose the best lens for what you need.
The modulation transfer function tells us how well a lens keeps contrast from the subject to the picture. It shows how much detail the lens can keep at different levels. Experts say the modulation transfer function is the size of the optical transfer function. The optical transfer function comes from a special math process called the Fourier transform. The modulation transfer function checks how much contrast stays in the image as details get smaller. This uses spatial frequency, which means how many lines or patterns fit in a certain space. When spatial frequency goes up, the modulation transfer function usually goes down. This means lenses have trouble keeping contrast with tiny details. The modulation transfer function is not a fixed number. It is a comparison, and people often set it to one at zero spatial frequency.
The modulation transfer function curve shows how well a lens keeps contrast at different detail sizes. This curve helps people see if a lens can make sharp and clear pictures.
The mtf is very important when picking or designing a lens. It lets people compare how lenses handle contrast and detail. The mtf curve shows the amount of image contrast compared to the object at each spatial frequency. When details get smaller, the mtf curve drops. This shows the lens’s limit for detail. Every part of a camera system, like the lens and sensor, has its own mtf curve. The whole system’s mtf is found by multiplying these curves. This gives a full idea of image quality.
Engineers use mtf data to make lenses better. Lenses with good materials and coatings have higher mtf values. Software helps designers make mtf curves better by fixing problems like distortion. The mtf affects how clear a picture looks, which is very important in science and industry. Good mtf measurements help people pick lenses that need to be sharp and clear. By looking at mtf, people can make smart choices and know the lens will work well for real jobs.
Selecting the right lens for mtf testing starts with knowing the lens type and its intended use. Photographers and engineers often choose a lens that matches their real-world needs. The environment plays a big role in mtf testing accuracy. Stray light can lower contrast and affect the results, so people should test the lens in a space with controlled lighting. Uniform illumination across the test chart is important because uneven lighting can change the mtf values. A clean, dust-free room helps keep the lens and equipment in top shape. Temperature and humidity should stay stable to avoid changes in the lens performance.
Tip: Minimize all outside factors during mtf testing. This helps ensure the results reflect the true quality of the lens.
Other environmental issues, like reflections or shadows, can also change mtf readings. People should check the setup for any unwanted light sources or objects that might affect the test. By controlling these factors, they can trust the mtf testing results.
Proper cleaning and inspection of the lens are key steps before mtf testing. People should always wear clean gloves, such as nitrile, to avoid leaving oils or dirt on the lens. Handling the lens by its edges keeps fingerprints off the optical surfaces. A bulb blower removes loose dust and debris without touching the lens. If the lens needs more cleaning, a small amount of lens cleaning solution goes on a lint-free cloth, not directly on the lens. Wiping should start at the center and move outward in circles. This method keeps dirt from spreading across the lens.
A clean, dry microfiber cloth or lens paper helps dry the lens after cleaning. People should only clean the lens when it looks dirty, since too much cleaning can cause scratches. Inspection works best in a well-lit, dust-free, and temperature-controlled room. Careful cleaning and inspection help the lens perform at its best during mtf testing.
Test charts are very important in mtf testing. They help people see how well a lens keeps detail and contrast. There are different kinds of test charts. Each type has good and bad points. The table below lists the most common test chart types for mtf and their main features:
| Test Chart Type | Advantages | Disadvantages |
|---|---|---|
| Reverse Projection | Fast; Cheap; Easy to use; Tests many points at once; Simple to learn | Results are not exact; Cannot measure contrast well; Depends on eyesight; Not much control over light |
| MTF Testing | Very accurate; Finds more lens problems; Ready-made tools; Works for many uses | Costs a lot; Tests one spot at a time; Does not notice stray light or real-world lighting |
| Slanted-Edge MTF | Tests many points at once; Free and paid software; Checks whole system including lens, camera, and lighting | Needs even lighting; Picking the right target can be hard; Can be used wrong |
| Camera Tests | Tests many points at once; Made for special uses; Can change easily; Checks whole system | Not much outside help; Hard to match results |
Many people pick slanted-edge mtf charts for lens mtf testing. These charts let them check more than one spot in the picture at the same time. They also work with lots of software.
A steady camera and mount are needed for good mtf testing. The camera must keep the lens still during the test. If it moves, the picture can get blurry and the mtf results will change. Tripods or special benches help hold the camera and lens steady. Some setups use special mounts to line up the lens with the test chart. Good alignment makes sure the test checks the lens, not mistakes from the setup. People should use remote triggers or timers so they do not shake the camera when taking pictures.
Software helps people study mtf data from lens tests. Many experts use 4Sight Focus software for mtf work. This tool works with interferometers and optical profilers. It gives real-time alignment, 2D and 3D views, and many data tools. Imatest is another top choice for mtf testing. It started from sfrmat software and is now used by many people. MTF Mapper is a free way to measure mtf. Quick MTF is a cheaper option. Some people use ImageJ plugins like ‘SE MTF 2xNyquist’ or the MTF plugin by Carles Mitja. Others write their own scripts in MATLAB or Python for special jobs.
Imatest: Paid, used by many for mtf
MTF Mapper: Free, liked for mtf tests
Quick MTF: Cheaper mtf tool
ImageJ plugins: Easy mtf tools
Custom scripts: Flexible mtf tests for experts
These tools help people get clear answers from lens mtf testing. The right software makes it simple to see how a lens works and to compare lenses.
Lens testing uses a few main ways to measure the modulation transfer function. Each way has good and bad points. The best way depends on the lens, tools, and how exact you need to be. The table below shows the most common mtf testing ways:
| Method | Principle / Approach | Advantages | Disadvantages / Limitations |
|---|---|---|---|
| Slanted-Edge | Uses a high contrast edge target at a slight angle; derives mtf from edge-spread function and its derivative. | Fast, flexible, costs less; checks many spots at once; software helps. | Can be affected by noise and light; picking the right target is tricky; mistakes can happen; easy to use wrong. |
| Frequency | Measures contrast at single spatial frequencies by manual measurement and plotting. | Easy to do. | People can make mistakes; hard to set up; not good for big systems; not used much now. |
| Scanning | Uses a tiny light source to capture spatial profiles; applies Fourier transform. | Cheaper; finds small changes in the lens. | Slow; takes a lot of time; not good for many tests. |
| Interferometry | Calculates mtf from pupil function or wavefront using Fourier transform. | Very exact; good for testing with certain colors. | Cannot test many colors; not used for all lenses; needs special tools. |
The slanted-edge way uses a chart with a sharp, dark edge at a small angle. The camera takes a picture of this edge. Software looks at how the edge spreads out. Then, the software finds the mtf by checking the line-spread function. This way is fast and checks many spots in one picture. Many people use it because there is free and paid software. But, this way can be bothered by bad light or noise. If the light is not even, the mtf numbers may be wrong. Picking the right chart is important. Mistakes in setup can cause errors, mostly with small details. The slanted-edge way helps stop pixel problems, as in ISO 12233.
Frequency ways check contrast at certain detail sizes. The user measures contrast at each size and makes a graph to get the mtf curve. This way is easy but can be slow and mistakes are common. Doing it by hand can cause errors. Scanning ways use a small light, like a pinhole, to move across the lens. The system records how the light spreads and uses a Fourier transform to find the modulation transfer function. Scanning can find small changes in the lens. But, it takes longer and is best for small groups or research.
Note: Line pairs and scanning ways often check only one spot at a time, so they are not good for big lenses.
Interferometry uses wavefront data from the lens to find the modulation transfer function. The system measures the wavefront or pupil function and uses a Fourier transform. This way gives very exact mtf numbers, mostly for a small range of colors. Interferometry works well for very exact lenses in labs. But, it cannot test many colors and does not work for every lens. You need special tools and training.
Tip: Interferometry is best for research and making top lenses, not for normal mtf testing.
Getting ready for mtf testing is the first thing to do. A good setup helps you get results you can trust. Here are the steps to follow:
Set up lights so the test chart is bright everywhere. Put the lights at angles between 35° and 45°. Do not put lights behind the lens or past 45°. This stops glare and shadows.
Use matte charts to stop glare. If you use semigloss charts, move the lights until you see less reflection but keep the light even.
Check that the light is the same all over the chart. The difference should be less than 20% for mtf tests. For color and tone, keep it within 5%.
Put the test chart on a flat, smooth surface like acrylic. This keeps the chart from getting bent or marked. Using pro mounting tools is best.
Always wear clean white cotton gloves to touch the charts. Store the charts in cool, dry places away from sunlight.
Make sure the camera and chart are level with each other. The camera can point down if needed.
Install and set up the right software, like Imatest, for taking pictures and checking mtf. Many programs work with different cameras.
Tip: Clean rooms and even lighting help lower noise and make mtf tests more correct.
Getting the lens and chart lined up right is very important for good mtf results. Even small mistakes can change the data a lot. To line things up:
Put the chart at the right distance from the camera. This keeps the lens focused and the test correct.
Make sure the center and corners of the chart are sharp. This helps stop mistakes from lens shape or camera tilt.
Try to keep tilt and weird angles as low as you can. A tilt of 1-2 degrees is okay but less is better.
Leave some white space above and below the bars on the chart. Try for 1-6% of the picture height. This helps check for distortion.
Do not put patterns near the chart edges. Use a light gray or plain background.
Use the scales on the chart to set the camera distance. The middle of the chart should be close to zero on the scale in the camera view.
Put the chart on a big foam board to keep it steady. Add a scale in millimeters to help line things up.
Clean the lens and chart before you start. Dust or smudges can make the picture less sharp.
Use more than one light at 30-45 degrees to stop shadows and reflections.
Note: Small mistakes in alignment (1-2%) are okay, but being careful gives the best mtf results.
Taking pictures for mtf testing means you must control the camera and room. Follow these steps:
Set the camera to its normal ISO to keep noise low.
Pick the best aperture for the lens to get the sharpest photo.
Use a remote or timer so you do not shake the camera.
Take more than one picture to make your results stronger.
Keep the lighting the same and under control. This stops fake contrast and keeps mtf numbers right.
Use strong mounts so nothing moves during the test.
Write down all camera settings and room details. This helps others do the same test.
Check your setup often with known standards.
Lighting is very important for mtf tests. Bad light or too much noise makes results less good. A contrast-to-noise ratio of 60 or more keeps mistakes low. Scattered or weak light can lower contrast and change the mtf numbers.
After you take the pictures, you need to study the data to get mtf values. Computers help make sure the results are right. The table below shows the main steps:
| Step | Description |
|---|---|
| 1 | Pick small parts of the image with lots of detail (like 500×500 pixels). |
| 2 | Use computer methods to check the image kernel for each part. |
| 3 | Check the energy concentration (EC) of the kernel to see if it is good; throw out kernels with EC that is too high or too low. |
| 4 | Change the image kernel to make the point spread function (PSF), then use a Fourier transform (FFT) to get the 2D mtf. Find mtf curves in both directions and pick values at the Nyquist frequency. |
| 5 | Average the mtf values from both ways to get the final mtf. |
Other ways to study the data include digital Fourier analysis, the knife-edge method, and the periodic target method. Each way has good and bad points. For example, the edge method works well if the image mtf is above 0.1 and the signal-to-noise ratio is above 20 dB. Noise and how much detail is in the image can change how correct the results are.
Tip: Turn off all image boost features, like contrast or noise fixes, when doing mtf tests. Use lossless image types so you do not lose data. Check all tools and follow the rules for the best results.
MTF charts help people check how sharp and clear a lens is. These charts have two sides called axes. The bottom side shows how far from the center to the edge, usually in millimeters. This lets people see if the lens works well all over the picture. The side going up and down shows modulation transfer. This number goes from 0 to 1. Bigger numbers mean the lens keeps more detail and contrast.
On an mtf chart, solid lines are sagittal and dashed lines are meridional. Sagittal lines go out from the middle. Meridional lines go around the center in circles. Thick lines (about 10 lines per millimeter) check contrast. Thin lines (about 30 lines per millimeter) check resolution.
If the lines are near the top (above 0.8), the lens is very sharp and clear. If the lines are above 0.6, the lens is good. If the lines are below 0.4, the lens does not work well. When solid and dashed lines are close together, the out-of-focus parts (bokeh) look smoother.
Lens makers test lenses at different apertures. By looking at the lines’ shape and height, people can tell how well the lens keeps detail and contrast in different parts of the picture.
MTF charts give important numbers that show how good a lens is. The table below explains these numbers and what they mean for photos:
| Metric | Description | What It Means for Photos |
|---|---|---|
| MTF50 | The spot where mtf drops to half its low-frequency value | Shows how sharp a lens looks to people |
| MTF50P | The spot where mtf is half its highest value | Gives a better idea of sharpness, even if the camera sharpens the picture |
| MTF area normalized | The area under the mtf curve, adjusted for the highest value | Shows real detail without being tricked by sharpening |
| MTF10, MTF20 | Spots where mtf is 10% or 20% of its low or highest value | Shows the tiniest details, but most people cannot see them |
| Shannon information capacity | Combines mtf, noise, and contrast loss into one score | Measures how well the lens and camera work together |
These numbers help people compare lenses and pick the best one. MTF50 and MTF50P are best for seeing sharpness people notice. Lower numbers like MTF10 and MTF20 show tiny details, but most people do not see them in normal pictures.
Getting good MTF results needs careful work and planning. Experts have some tips to help people do better:
Make a clear plan for each test. People should know what they want to check before picking a way to test.
Try more than one way to test. Using slanted-edge, reverse projection, and camera tests together gives a better idea of how the lens works.
Keep the testing place steady. Good lighting and a clean room help show the real quality of the lens.
Learn what each test is good and bad at. This helps people pick the best one for their job.
Use special MTF test benches if you can. These tools give results you can trust and check again.
Match the lens MTF with the image sensor’s MTF. This helps stop problems like jagged lines and makes edges look smoother.
Build the vision system with care. A good setup can stop problems from pixels or changes inside each pixel.
Pick longer focal length or bi-telecentric lenses to lower bending from the lens and sensor.
Know how sensor types are different. Back-side illuminated (BSI) sensors usually have less bending than front-side illuminated (FSI) sensors.
Tip: Picking the right way to test and building the system well makes MTF testing work better and gives more correct results.
Many people make easy mistakes when doing MTF testing. These mistakes can give bad results or wrong ideas:
Not cleaning or checking the lens before testing.
Using bad lighting or letting extra light hit the chart.
Not lining up the camera and chart the right way.
Only using one way to test and missing important things.
Not matching the lens and sensor, which can cause picture problems.
Forgetting to turn off camera tools like sharpening or noise fixes.
Not writing down test settings or room details.
Not thinking about how the sensor type changes the results.
Note: Staying away from these mistakes helps people get results they can trust and makes it easier to compare lenses.
Many experts use special software to measure the Modulation Transfer Function (MTF) of lenses. Studies that are checked by other scientists often say edge analysis algorithms are best for measuring MTF. These algorithms, especially ones that follow the IEC 62220-1 standard, give results that are correct and can be repeated. The slanted-edge technique is popular because it works with many lenses and cameras. Most new MTF software uses this way.
Here are some common MTF software and tools:
Imatest: This program uses the slanted-edge method and works with many cameras.
MTF Mapper: This free tool helps people measure MTF from edge images.
Quick MTF: This software gives an easy way to check how sharp a lens is.
ImageJ with MTF plugins: Scientists use this open-source tool for special checks.
Matlab code: Some experts write their own scripts for special tests.
QDA Miner: This is not a main tool for MTF but some researchers use it to study data about MTF skills.
Many of these tools use the edge technique, which studies show is good for careful MTF checks.
People who want to know more about MTF measurement can find good information in books, rules, and online guides. The sources below are trusted by many:
Image Science by J.C. Dainty and R. Shaw explains MTF in detail.
The ISO 12233 standard gives the rules for measuring camera MTF, especially with the slanted-edge method.
The sine wave technique uses special targets, and software for this is from the Mitre Corporation.
The Photographic and Imaging Manufacturers’ website has Adobe Photoshop plug-ins and Matlab code for slanted-edge checks.
RLG Diginews has a guide that explains how MTF works and why it is important.
These resources help both new learners and experts understand MTF testing and get better at it.
Doing each step in MTF testing helps you get good results for any lens. Having a clear plan, like in trusted surveys, makes the test more steady and correct.
Getting ready and picking the right way to test makes things more exact, as you can see in the table below:
| Frequency (lp/mm) | Average MTF | CV (%) |
|---|---|---|
| 1.0 | 0.946 | 0.53 |
| 6.0 | 0.400 | 4.50 |
You can use this guide when you test lenses later. Trying new ways, like point source MTF testing, can show if a lens is not lined up right and make your results better. If you have problems, keep the test area the same and make it like real life to check the lens better.
Tell us about your lens tests or ask questions in the comments to help everyone learn.
MTF stands for Modulation Transfer Function. It shows how well a lens keeps detail and contrast in an image. Higher MTF values mean sharper and clearer pictures.
Yes, people can test MTF at home using printed test charts, a camera, and free software like MTF Mapper. Careful setup and lighting help improve accuracy.
Lenses have different designs, glass types, and coatings. These factors change how much detail and contrast each lens can keep. Even lenses from the same brand can show different MTF results.
Yes. The camera sensor can change MTF results. Back-side illuminated (BSI) sensors often give higher MTF values than front-side illuminated (FSI) sensors because they collect more light and reduce blur.
