Imatest will be at SPIE Photonics West 2020

Imatest is attending and exhibiting at SPIE Photonics West in San Francisco, February 1-6, 2020. (more…)

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San Jose, CA Imatest Training Course – November 6-7, 2019

Imatest in San Jose

Imatest representatives will visit San Jose, CA, November 6-7, 2019, to offer a paid two-day training course to professionals using or considering Imatest software to improve their image quality testing processes.

Imatest Training Course - San Jose, CA November 6-7, 2019

Two-Day Training Course

The Training Course on November 6 & 7 offers attendees insight on the full capabilities of Imatest software in both research & development and manufacturing environments.

Training will run from 8:30 am to 5:30 pm each day, depending on questions. The event location is at the Larkspur Landing Hotel in Campbell, CA.

Visit our training page to view a detailed training schedule.

Group Discounts

Enroll 2-4 attendees to receive 20% off per attendee.

Enroll 5 or more attendees to receive 30% off per attendee.

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Imatest Support Renewal

Maintaining current support on your Imatest license allows you to access all new version releases and updates during the support period and access our support team for technical assistance with your software and projects. (more…)

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Introducing Imatest 5.2

BOULDER, CO -September 12, 2019—Imatest, a global image quality testing solution provider is pleased to announce Imatest 5.2. With this new Imatest release, the Imatest team adds several new features to provide better analysis tools and new options. (more…)

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Imatest and Furonteer Collaboration Finalist for Best Validation/Simulation Tool Award

BOULDER, CO -September 4, 2019—Imatest, a global image quality testing solution provider, and Furonteer, an automation equipment manufacturer, are finalists for the Best Validation/Simulation Tool Award provided by AutoSens, a forum for Advanced driver-assistance systems (ADAS) technologists. (more…)

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Imatest Announces Modular Test Stand

Boulder, Colorado, August 30, 2019—Imatest, a global provider of image quality testing solutions, now offers a Modular Test Stand (MTS) that enables you to produce superior cameras while significantly reducing time spent in the lab. (more…)

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AutoSens Brussels, September 17-19, 2019

Imatest will attend AutoSens in Brussels on September 17-19, 2019. AutoSens is a 3-day workshop, conference, and exhibition advancing the education for and development of vehicle perception technology. It brings together over a thousand minds in vehicle perception, ADAS, and autonomous vehicles twice a yearin Detroit, Michigan USA in May, and Brussels, Belgium in September. (more…)

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July 2019 Newsletter

Our newsletter features our products, company news, educational image quality articles, Imatest events, and relevant industry articles. Subscribe to receive our newsletters in your inbox. (more…)

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June 2019 Newsletter

Our newsletter features our products, company news, educational image quality articles, Imatest events, and relevant industry articles. Subscribe to receive our newsletters in your inbox.

Imatest-Furonteer Partner to Reduce Geometric Camera Calibration Time

Imatest and Furonteer Reduce Camera Instrinsic Calibration Time

Imatest and Furonteer partnered in early 2019 to provide high throughput production machines for geometric calibration of single and multicamera devices.

 

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Imatest software testing program for early access - Pilot Program

Join our Pilot Program

A new Imatest software release is coming soon. Join our pilot program for early access to the new version in testing.

 

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Imatest and Furonteer Reduce Camera Intrinsic Calibration Time with Automated Machines

BOULDER, CO – JUNE 25TH, 2019 — Imatest, a global image quality testing solution provider, partnered with Furonteer, an automation equipment manufacturer, in early 2019 to provide production machines for geometric calibration of single and multicamera devices. (more…)

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Shanghai, China – Imatest Training Course – November 11-12, 2020

Imatest in Shanghai

Imatest engineers will visit Shanghai, China, November 11-12, 2020, to offer a paid two-day training course to professionals using or considering Imatest software to improve their image quality testing processes. A free information seminar will be offered on November 10.

Shanghai 2020 training image

Two-Day Training Course

image (2)

The training course offers attendees insight into the capabilities of Imatest software in both research and development and manufacturing environments.

After taking this course, you will have:

  • An understanding of key image quality factors
  • Practical knowledge of how to apply Imatest software to measure the factors
  • An overview of how to set up and tailor your test lab for accurate measurements

It is highly recommended you have a basic understanding of how cameras work (see recommended prerequisites). A detailed training schedule is also available.

Date and Time: November 11-12, 2020; 09:00 – 18:00, depending on the questions.

Location Details: TBD

Instructor: Henry Koren, Director of Engineering, Imatest

Registration: Contact a reseller in your area or cick the registration button below.

Register for Two-Day Training

Free Information Seminar

If you are interested in finding out more about how Imatest software can improve your image quality testing, we encourage you to come to our free information seminar.

Date and Time: November 10, 2020; time: TBD

Location: TBD

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Seoul, South Korea – Imatest Training Course – October 20-21, 2020

Imatest in Seoul

Imatest engineers will visit Seoul, October 20-21, 2020, to offer a paid two-day training course (October 20-21) to professionals using or considering Imatest software to improve their image quality testing processes. A free information seminar will be offered on October 19. 

Seoul 2020 training image

Two-Day Training Course

image (2)

The training course offers attendees insight into the capabilities of Imatest software in both research and development and manufacturing environments.

After taking this course, you will have:

  • An understanding of key image quality factors
  • Practical knowledge of how to apply Imatest software to measure the factors
  • An overview of how to set up and tailor your test lab for accurate measurements.

It is highly recommended you have a basic understanding of how cameras work (see recommended prerequisites). A detailed training schedule is also available.

Date and Time: October 20-21, 2020; 09:00 – 18:00, depending on the questions.

Location Details: TBD

Instructor: Henry Koren, Director of Engineering, Imatest

Registration: Contact a reseller in your area to register for this two-day course or click the registration button below.

Register for Two-Day Training

Free Information Seminar

If you are interested in finding out more about how Imatest software can improve your image quality testing, we encourage you to come to our free information seminar.

Date and Time: October 19, 2020; Time is TBD

Location: TBD

Register for Information Seminar

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San Jose, CA – Imatest Training Course – August 6-7, 2020

Imatest in San Jose

Imatest engineers will visit San Jose, California between August 6-7, 2020 to host a paid two-day training course to professionals using or considering Imatest software to improve their image quality testing processes.

Image Quality Testing Training with Imatest on August 6-7, 2020

Two-Day Training Course

image (2)

The training course offers attendees insight into the capabilities of Imatest software in both research and development and manufacturing environments.

After taking this course, you will have:

  • An understanding of key image quality factors
  • Practical knowledge of how to apply Imatest software to measure the factors
  • An overview of how to set up and tailor your test lab for accurate measurements.

It is highly recommended you have a basic understanding of how cameras work (see recommended prerequisites). A detailed training schedule is also available.

Date and Time: August 6-7, 2020; 09:00 – 18:00 (depending on questions)

Location Details: TBD

Instructor: TBD

Register for Two-Day Training

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Germany – Imatest Training Course – March 24-25, 2020

Imatest in Munich, Germany

In light of the COVID-19 Coronavirus, this training course will be held remotely. We regret that we are unable to host this event in person. All registrants will receive a $300 credit towards a future purchase.

Imatest engineers planned to visit Germany on March 24-25, 2020 to host a paid two-day training course to professionals using or considering Imatest software to improve their image quality testing processes. This course will now be held remotely.

Germany 2020 training image

Two-Day Training Course

image (2)

The training course offers attendees insight into the capabilities of Imatest software in both research and development and manufacturing environments.

After taking this course, you will have:

  • An understanding of key image quality factors
  • Practical knowledge of how to apply Imatest software to measure the factors
  • An overview of how to set up and tailor your test lab for accurate measurements

It is highly recommended you have a basic understanding of how cameras work (see recommended prerequisites). A detailed training schedule is also available.

Date and Time: March 24-25, 2020; 09:00 – 18:00 (depending on questions)

Location Details: Remote Training. Details for attending will follow registration. 

Instructor: Henry Koren

Register for Two-Day Training

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P2020 Automotive Engineering Technology May 2019

Imatest attended the P2020 meeting on May 13 and 14, 2019 in Ann Arbor, Michigan. Paul Romancyzk, PhD., Senior Imaging Scientist, and Rob Sumner, Lead Engineer, represented Imatest. Paul co-led the discussion on Color Separation within the Image Quality for Machine Vision subgroup.

(more…)

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Imatest will Attend AutoSens Detroit on May 14-16, 2019

Imatest will attend AutoSens in Detroit on May 14-16, 2019. AutoSens is a 3-day workshop, conference, and exhibition advancing the education for and development of vehicle perception technology. It brings together over a thousand minds in vehicle perception, ADAS, and autonomous vehicles twice a yearin Detroit, Michigan USA in May, and Brussels, Belgium in September. (more…)

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Using Arbitrary Charts for Development of the P1858 Variation Combo Chart

The release of Imatest 5.0 introduced a number of powerful new features, including the Arbitrary Charts module which enables Imatest analysis of test chart designs which would be otherwise unsupported by the software. This new module allows user-defined chart layouts for any situation which requires one.

The primary concept of Arbitrary Charts is that the user supplies a chart-definition text file which declares the location and properties of features on a test chart. The features can be placed in essentially any configuration and Imatest will still be able to automatically analyze the chart. (more…)

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Imatest at IEEE P2020

Imatest sent two engineers to the IEEE P2020 Automotive Imaging Quality face-to-face meeting in Dusseldorf, Germany this past February in 2019. The IEEE P2020 standard, which is still in development, aims to define KPIs and test procedures to address the many challenges relevant (and often unique) to automotive imaging. (more…)

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Compensating MTF Measurements for Chart Quality Limitations

Camera MTF (sharpness) measurements are subject to a number of variations, some of which, like noise, are random and difficult to control, and some of which are systematic and can be corrected. Variations caused by limitations in chart sharpness are in the latter category. These variations are also affected by the Field of View (FoV) of the image used to test the camera, which is closely related to chart size for charts designed to fill the camera frame. For a given print technology, increasing the FoV, which typically means increasing the spacing between the chart and camera, will increase the measured MTF— making it more accurate. However, there are many practical situations where space is limited and small FoVs are called for, and chart sharpness can significantly affect the measurements. This post describes a method for quantifying and correcting such measurement variations. The method has the following steps.

  1. Measure the test chart MTF and fit it to an equation.
  2. Compensate camera MTF measurements for the test chart sharpness.
  3. Based on measurements with and without compensation for a variety of charts and test magnifications mtest, determine the conditions where (a) chart quality is good enough so no compensation is needed, and (b) chart quality is too low to be reliably compensated.

There is little mention of test chart sharpness in the literature, perhaps because when the ISO 12233:2000 standard was created, high-resolution cameras had only about one megapixel, and hence it was easy to print adequate test charts.

View the video below for Norman Koren’s talk on Compensating MTF Measurements for Chart Quality Limitations. This article describes the concept in detail. 

Measuring test chart MTF

The first step in compensating camera MTF measurements is to measure the test chart MTF. This should be done by photographing the same features used to measure camera MTF. We describe the process for slanted-edges, but other patterns, such as Siemens stars, could also be used. Since we have found that edge sharpness in inkjet charts can depend on the edge orientation, we measure up to four edges (the left, right, top, and bottom of a dark square on a light background).

We performed our chart measurements with a 24 Megapixel APS-C camera that has a 23.5×15.6mm sensor with a 3.88-micron pixel pitch. We used a mechanically-focused 60mm prime macro lens that had a scale that displayed magnification. This enabled us to maintain constant chart magnification mchart for our tests, which is difficult to accomplish with lenses that have electronic focusing. We used mchart = 1:2 (0.5×) for inkjet charts and mchart = 1:1 (1×) for photographic paper and film charts, which are sharper. Chrome-onGlass charts are too sharp to be measured with this setup.

FIGURE 1. CHART MTF MEASUREMENT SETUP

The setup (Fig. 1) consists of a custom-machined aluminum base and a sturdy aluminum extrusion column. Fine focus is controlled by a micrometric positioning sliding plate. The lens is fixed at mchart = 1:2 or 1:1. Simple adjustments are used to keep the sensor plane is parallel to the test chart. A non-flickering LED ring light is used for reflective charts; a light box is used for transmissive charts.

When calculating chart MTF it is important to select large enough Regions of Interest (ROIs) to obtain consistent results. For inkjet charts, which can have rough edges, especially when photographed at chart magnification mchart = 1:1 (1×), MTF50 can vary by as much as ±10% for small ROIs. To obtain good measurement consistency, we photographed inkjet charts at mchart = 1:2 (0.5×), using region sizes ≥ 900×1300 pixels. For chart media other than inkjet, all of which are finer, we used mchart = 1:1.

Fitting measured MTF to an equation

The measured chart MTF must be fit to an equation in order to reliably perform MTF compensation, where the measured camera MTF is divided by the model of the chart MTF projected on the sensor. We have chosen a function that (a) is simple– only two parameters, (b) is a good match to our chart MTF measurements, and (c) is guaranteed to decrease at high spatial frequencies.

Equation (1)

MTFchart(fchart) = exp (-afchart – (bfchart)2)

Where fchart is the spatial frequency in Cycles/Object mm on the chart. a and b are found using an optimizer to match Equation (1) with MTF measurements for f ≤ f30, the first frequency where MTF drops below 0.3 (30%). This is done because noise can dominate MTF measurements for f > f30, as illustrated below (Fig. 3).

Parameters a and b are stored in a file along with metadata (the name of the test chart image file, chart magnification mchart, date, etc.) This file is read into the analysis program when chart compensation is to be applied. We have found that, apart from old charts made with unknown printers and settings, charts don’t need to be measured individually. A compensation file based on media, printer type, and print settings should be sufficient.

Chart MTF measurement examples

Fig. 2 illustrates an MTF measurement for a horizontal slanted-edge on an inkjet chart photographed with mchart = 0.5×. The upper curve shows the average edge profile. The rise distance (14 pixels) is large enough so that camera software sharpening will not affect the results. The lower plot shows the measured MTF (bold black curve) and the fit to the MTF (bold cyan curve) from Equation (1) for f < f30. The parameters for this fit are a = 0.10507 and b = 0.09407.

FIGURE 2. INKJET CHART MTF MEASUREMENT

Curious artifacts sometimes appear in chart MTF measurements. Figure 3 is the MTF of an edge from a chart printed with the edges along the directions of paper and print head motion (not slanted). Test charts printed this way are cut slanted. A strong MTF response peak, visible around 13.5 Cycles/Object mm, appears to be caused by periodicity in the inkjet dots. (It’s not present when edges are printed slanted.) Fortunately, it’s well outside the analysis passband as well as the frequencies used to calculate a and b in Equation (1).

FIGURE 3. INKJET CHART MTF SHOWING RESPONSE PEAK

There are sometimes surprises in the MTF measurements. Chart MTF for photographic film printed on an LVT (Light Valve Technology) printer have a response indicative of sharpening (Fig. 4), apparently caused by uneven depletion of the film developer near edges—familiar to the author from his wet darkroom days. Note that the curve from Equation (1) (cyan) is a good match to the MTF curve, which has a sharpening bump.

FIGURE 4. COLOR LVT FILM MTF SHOWING CHEMICAL SHARPENING

MTF compensation

To calculate MTF compensation, the chart spatial frequency in Cycles/Object mm, fchart, must be transformed into Cycles/Pixel (C/P) on the image sensor. For test magnification mtest,

Equation (2)

f(C/Obj mm) = f(C/P) × mtest × pixels/mm

The MTF of the chart projected on the image sensor is:

Equation (3)

MTFprojected(f) = MTFchart(f(C/P) × mtest × pixels/mm) 

Finally, the chart-compensated MTF is:

Equation (4)

MTFchart−comp(f) = MTFmeasured(f)/MTFdiv(f)

Where:

Equation (5)

MTFdiv(f) = max(MTFprojected(f), 0.3)

Limiting the minimum value of MTFdiv to 0.3 prevents excessive high-frequency noise boost. And as we have shown in Fig. 3, chart MTF measurements at frequencies where MTF drops below 0.3 (f > f30) can be strongly affected by chart noise (especially for inkjet charts), and hence are not reliable.

Camera testing and verification

The effects of chart compensation were tested using a 10-megapixel digital camera (a Panasonic Lumix LX5 from 2010) that had the following:

  • A small 5.4×8.1mm sensor with 2.14-pixel size to ensure low test magnification mtest for most of the charts, intended to keep lens performance relatively consistent throughout the tests.
  • RAW output to minimize nonlinear signal processing commonly found in JPEG files.
  • A high-quality zoom lens set to 50mm (35mm-equivalent) at f/4.

With this camera, we expected MTF measurements to be affected only slightly for the largest charts, which are designed to fill the image frame, and hence have the largest Fields of View (FoVs). We expected MTF measurements to be degraded significantly for the smallest charts.

FIGURE 5. SOME OF THE TEST CHARTS USED TO VERIFY MTF COMPENSATION

Fig. 5 illustrates the two types of slanted-edge chart used in our testing: Imatest SFRplus (a grid of slanted squares with bars at the top and bottom) and eSFR ISO (an enhanced version of the ISO 12233:2014 edge SFR chart). Both charts have 4:1 contrast slantededges, as recommended in ISO 12233:2014. Sizes varied over a range greater than 10:1. These charts were printed over several years on a variety of media— inkjet and photographic paper (reflective), and color photographic film (transmissive).

The reported Fields of View (FoVs) are typically slightly larger than the active area of these charts. Both chart types have geometrical features that facilitate the calculation of test magnification mtest. For each image, four edges — Left (L), Right (R), Top (T), and bottom (B) from the square closest to the chart center — were analyzed for compensated and uncompensated MTF.

Since we didn’t know the history of the charts, MTF for sample edges was measured individually for each chart.

 

Compensated and uncompensated results

MTF measurements in Figures 6-9, each from an edge near the center of four very different test charts, illustrate the effects of chart MTF on results. Uncompensated MTF is shown as a magenta line. Compensated MTF is a bold black line. MTFdiv is a cyan line. MTF50 (the spatial frequency where MTF drops to 50% of its low-frequency level) is the key summary metric for comparing results.

FIGURE 6

The large inkjet chart in Fig. 6 (147×97cm Field of View FoV) has MTF50 = 1166 LW/PH (uncompensated) and 1345 LW/PH (compensated). Correction makes only a small difference in the MTF measurement, as expected. The MTF50 difference is largely caused by a small noise-related response bump.

FIGURE 7

The small inkjet chart in Fig. 7 (32×21cm FoV) has MTF50 = 922 LW/PH (uncompensated) and 1302 LW/PH (compensated). Correction makes a significant difference. Results would be inaccurate without it. f30 is far enough above the Nyquist frequency to ensure good measurement results.

FIGURE 8

The small, low-quality inkjet chart in Fig. 8 (25×17cm FoV) has f30 well below the Nyquist frequency. Results are not reliable. This chart is inadequate for measuring the quality of this camera system.

FIGURE 9

The small but extremely high-quality LVT film chart in Fig. 9 (26×17cm FoV) has MTF50 = 1466 LW/PH (uncompensated) and 1445 LW/PH (compensated). The chart MTF response bump causes a slight decrease in the corrected MTF response.

Results summary

Figures 10 and 11 contain detailed results for five SFRplus and five eSFR ISO charts of various sizes and media. This somewhat arbitrary grouping was chosen because the results would not all fit on a single figure. The four groups of five bars on the left (light magenta background) represent uncompensated MTF50. The four groups of five bars on the right (light yellow background) represent compensated MTF50. Compensated MTF50 is generally larger and much more consistent, as indicated in Table 1, below.

Each group of five bars represents MTF50 results for slanted edges from different charts. Groups are labeled by the edge near the image center used for analysis. The four groups on the left (L, R, T, B) contain uncompensated MTF50. The four groups on the right (L comp, R comp, T comp, B comp) contain the compensated MTF50 of the corresponding edges.

FIGURE 10. SUMMARY RESULTS FOR FIVE SFRPLUS CHARTS UNCOMPENSATED MTF50 ON LEFT; COMPENSATED ON RIGHT.

In Fig. 10, the five bars in each group are for (1) a large inkjet chart (124×82 cm FoV), (2) a medium inkjet chart (49×32 cm FoV), (3) a small inkjet chart (25×17 cm FoV), (4) 8×10-inch color LVT film (26×27 cm FoV), and (5) small color LVT film (14×9 cm FoV).

The medium and small inkjet charts showed the greatest improvement. The small LVT chart may have had consistently lower corrected MTF50 because it had a larger magnification than the other charts, which might have affected lens performance.

FIGURE 11. SUMMARY RESULTS FOR FIVE ESFR ISO CHARTS UNCOMPENSATED MTF50 ON LEFT; COMPENSATED ON RIGHT.

In Fig. 11, the five bars in each group are for(1) a large inkjet chart (147×97 cm FoV),(2) a medium-large photographic paper chart (126×84 cm FoV),(3) a medium-large inkjet chart (129×83 cm FoV), (4) a medium inkjet chart (65×42 cm FoV), and (5) a small photographic paper chart (32×21 cm FoV). The small photographic paper chart showed the greatest improvement.

The key takeaway from Figures 10 and 11, summarized in Table 1, is that compensated results are larger and have a lower standard deviation σ, i.e., they are more consistent and hence more accurate.

TABLE 1. SUMMARY RESULTS FOR FIGURES 10 & 11

Predicting test chart suitability

Equations (1) through (5) can be used to predict the suitability of a test chart for a specific application.

We should note that our guidelines for chart suitability assume that the camera is relatively sharp, i.e., not out of focus or blurred for another reason, such as poor lens quality. A reasonable criterion for a “sharp camera” is that it makes good use of available pixels, which would be the case when the unsharpened MTF50 > 0.1 Cycle/Pixel (C/P). Typical values are around 0.15 – 0.3 C/P for high-quality cameras.

After running numerous images, we developed the following guidelines for chart suitability, based on the projected chart MTF at the Nyquist frequency (0.5 C/P), MTF@ fNyq, on the image sensor.

TABLE 2. GUIDELINES FOR TEST CHART SUITABILITY

Fig. 12 shows results of a test chart suitability calculation for the chart/camera combination of Fig. 7. The compensation file had a = 0.1138 and b = 0.07027. Three of the following four parameters are manually entered.

  • Vertical field = 212 mm
  • µm per pixel = 2.14
  • Sensor height = 5.431 mm
  • Magnification = 0.02562

In typical operation the three geometrical parameters (vertical field, µm per pixel, and sensor height) are entered, and magnification mtest = sensor height / vertical field. From Table 2, we see that the key result, MTF@ fNyq = 0.41, indicates that the chart is being used close to its operating limit (MTF@ fNyq = 0.3), and MTF compensation is definitely required.

Limitations

Analysis is not reliable at spatial frequencies where the test chart MTF projected on the image sensor, MTF@ fNyq, drops below 0.3. This is well beyond the normal recommended limits.

Greater care is required when analyzing chart measurements. The correct compensation file should be specified and the correct test magnification mtest (or geometric parameters for calculating mtest) must be entered.

Chart compensation does not (yet) work well for strongly barrel-distorted (fisheye) images, where radial magnification is a function of distance from the image sensor, and hence radial and tangential magnification may differ.

Noise at high frequencies– especially above fNyq – may be strongly boosted. The response above fNyq should usually be ignored.

Conclusions

MTF compensation improves the consistency and accuracy of camera MTF measurements made from different test charts (often at different locations), especially when charts are used near their megapixel limits. Some MTF variation, primarily due to noise, remains after compensation. In our verification tests we may have observed some MTF variation caused by differences in lens performance at different test magnifications.

MTF compensation files should be created for each printer/media/setting combination. Except for old charts where these details are not known, charts don’t need to be measured individually. We have determined two limits related to MTF compensation:

  1. An upper limit, MTF50 @ Nyquist ≥ 0.9, beyond which chart compensation has little effect,
  2. A lower limit, MTF50 @ Nyquist < 0.3, beyond which compensated results are unreliable,

MTF compensation effectively doubles the megapixel usability limits for most test charts.

We have been using the chart MTF measurement techniques described here to improve the quality control of our printed test charts.

eSFR ISO Slanted Edge Chart - Select a Chart Landing Page

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Standards

ISO 12233:2017 – Electronic still picture imaging – Resolution and spatial frequency response.

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Imatest Branded Lightboxes and Light Panels

We are pleased to announce that beginning January 2019, we are offering Imatest branded light panels and boxes. Imatest has responded to feedback from our customers by creating these two new uniform light sources. (more…)

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