# Avoiding reflections on transmissive charts for dynamic range and flare testing

The testing of dynamic range and flare requires a proper test chart and environmental setup to get accurate results.High precision and high-density chart technologies such as photographic film or chrome on glass come with the disadvantage of glossiness which makes them susceptible to specular reflections on the target. This affects the use of dynamic range or contrast resolution and backlit flare targets that lack anti-reflective patches.

The goal of the backlit test setup is to maximize the fraction of light that is coming directly from your light source, through your test target, and into your lens, Any additional light that is present in your system can disrupt your measurements either by causing reflections on the analysis patch of your target, or otherwise introducing additional flare (veiling glare) into the image.

As the optimal lens and camera body housing will be manufactured with anti-reflective coating, it is good to take a similar approach with your test environment.  Nothing is actually entirely black, but dark, opaque materials come in many different forms. These can be characterized by their total hemispherical reflectance (THR).

Here are how some dark materials compare:

 Product THR (vis+NIR) Notes Black Paint 5-6% Not dark enough Black Felt 2.5% Flexible and low-cost Acktar black 1.5% Comes on adhesive foil Vantablack 0.17% Costly, not durable, dangerous to humans

For general testing purposes, we use black felt for covering our darkened test box

### Block all light from entering or reflecting inside the testing environment

For accurate testing, you should create a dark space where no outside light is able to enter, and as much internally generated light is absorbed. Here is a diagram of a test environment:

### Minimize internal direct reflections

The more that the surfaces in your test environment are lit up, the more they will become reflections in the glossy chart.

The body of the camera under test or even just glass of a camera lens can reflect back onto a test chart.This is especially important incident towards dark analysis regions.

If using Imatest charts that are properly centered, the reflection might not fall on to a dark analysis region for dynamic range measurement. Here is an example of a reflection of a dev kit PCB that would disrupt dynamic range or contrast resolution measurement:

Reflective camera parts should be blocked by black masks. The entire area behind your camera will directly be reflected back, so this environment should be made as dark as possible.

### Minimize other internal light emissions

Sensor development kits often have blinking LED’s that reflect directly, Front facing cameras with displays that are not disabled or blocked off can be particularly problematic.

# DMX Lighting Control Software

Lights such as the Kino Flo Select 31 LED use a DMX control interface to signal changes of light level and color temperature.

DMX is an open protocol and there are a large number of possibilities for hardware and software control. I’ve tried out several of these are more oriented to stage control

For DMX controller hardware I have personally tried and will recommend the Enttec DMX USB Pro controller worked well for us.
For computer control software with a user Interface, the one that has worked best for me so far is the Q Light Controller Plus (QLC+) which has nice cross-platform support.

For light control software that provides an automated API, the best one I have found, and the one we use to automatically control lights in our lab is the Open Lighting Architecture (OLA). The downside of this is that it only has good support for Linux. I have attached a python script that includes an example OLA calls, along with calls to an isolight puck, which you can overlook.  Here is a basic call to set the lights to middle color temp and maximum intensity:

from ola.ClientWrapper import ClientWrapper
intensity = 255
cct       = 127
universe = 1
data      = array.array('B')
data.append(intensity)
data.append(cct)
data.append(intensity)
data.append(cct)
wrapper = ClientWrapper()
client = wrapper.Client()
client.SendDmx(universe, data, DmxSent)

Our goal for Imatest 2020.1 is to have an instrument control interface built into Imatest Master that can directly communicate with DMX hardware.

# Error in Extracting CTF file

Error Message: Error in extracting CTF file to ‘C:\ProgramData\Imatest\mcr_cache\4.5\Master\mcrCache9.0.1\imates0’. Details: ‘Could not set last modified time: C:/ProgramData/Imatest/mcr_cache/4.5/Master/mcrCache9.0.1/imates0/toolbox/imaq/imaqextern/drivers/win64/genicam/genICam_v2_4/redist/Microsoft_VC80_CRT_x86_x64.msi: Broken pipe

Solution:

Your system is having trouble extracting Mathwork’s CTF archive. Here is what the possible causes are:

1. Permissions issue. For example if the application is unable to delete old directory or create a new one.
2. Time stamp issue. The CTF-file is re-extracted only when the time stamp on the CTFarchive is newer than the time stamp on the _mcr directory. If somehow an out-of-date _mcr folder has a newer time stamp than the CTF-file, the new CTF-file will not be extracted and there will be errors when running the application.
3. Extraction issue. If some error occurred during CTF extraction, there could be a problem where some of the encrypted M-files are of an old version and others are the new versions. This could cause the application to partially run and then only have an error when it runs into an old encrypted M-file.
4. Installer issue. If the _mcr directory is already in the package, the installer may not be updating all files properly leaving some older files in the _mcr directory thinking that the files already exist.
So, here are the steps you should try to resolve this:

1. Delete old MCR directories on your machine. These can be found at C:\Program Files\MATLAB\MATLAB Runtime, delete the contents of this folder.
2. Run the Imatest installer again as administrator, ensuring that the “Matlab Libraries” checkbox is checked and that you are running the full installer rather than the upgrade installer:

3. After the installer finishes, run Imatest as administrator.

If this process does not fix the issue please email us, support@imatest.com.

# Electronic Imaging 2018

We are pleased to announce that we will return to the IS&T Electronic Imaging conference in 2018, to take place from January 28 – February 1 in Burlingame, CA. The conference will be held at the Hyatt Regency San Francisco Airport and will feature 20 technical conferences covering a variety of electronic imaging topics, ranging “from image sensing to display and hardcopy to machine vision in use in transportation systems” (Electronic Imaging).

We will have a booth in the exhibition hall and will be demonstrating our software and test charts. Please contact us to meet with our image quality experts.

Additionally, Norman Koren will be presenting his paper, “Measuring the impact of flare lighting on dynamic range” on Monday, January 29, 2018 at 3:30 pm.

The dynamic range of recent HDR image sensors, defined as the range of exposure between saturation and 0 dB SNR, can be extremely high: 120 dB or more. But the dynamic range of real imaging systems is limited by veiling glare (flare light), arising from reflections inside the lens, and hence rarely approaches this level. Veiling glare measurements, such as ISO 18844, made with black cavities on white fields, result in large numbers that are difficult to relate to dynamic range. Camera dynamic range is typically measured from grayscale charts, where veiling glare depends on the design and layout of the chart, leading to inconsistent results. We discuss the interaction between veiling glare and dynamic range measurements and the need for standardization of test conditions. We also propose a new dynamic range definition and a new test chart design for directly measuring the visibility of low contrast features over a wide range of scene brightness, which is important for real-world applications, especially in the automotive and security industries where the visibility of people and obstacles in shadow regions is critical. Unlike standard grayscale charts, the new test chart provides meaningful results when tone mapping is applied.

# Cologne, Germany Training Course

## Imatest in Cologne, Germany

Imatest representatives will visit Cologne, Germany September 24-25, 2018 to offer a paid 2-day Training Course to professionals using or considering Imatest software to improve their image quality testing processes.

## 2-day Training Course

The training course offers attendees insight on the full capabilities of Imatest software in both research development and manufacturing environments. Training starts at 09:00 and will end at 17:00 – 18:00, depending on questions.

When: September 24-25th, 2018

Location: TBA.

View the detailed Training schedule.

# 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. (more…)

# Using Arbitrary Charts Video Series

This series of short videos provides an introduction to the Arbitrary Charts module. Learn how to develop Chart Definition Files

Oct. 25, 2017

Arbitrary Chart Definition Part 1: In this video, we introduce chart definition JSON files, their structure, and purpose in the Arbitrary Charts module.

# Five reasons to use Imatest 5.0

This week, we launched Imatest 5.0. We built Imatest 5.0 to provide users with a streamlined workflow for more efficient image quality analysis. Here are five reasons to start using Imatest 5.0 today.

# Imatest IS Discontinued with Image Acquisition now Available in Imatest Master

As of Imatest 5.0, Imatest Master now features image acquisition capabilities. Previously, image acquisition capabilities were supported by Imatest IS, which has been discontinued as a separate product. This provides all of our customers with access to the acquisition library. The library supports direct acquisition from a wide range of frame grabbers and cameras, as well as industry standard interfaces. Direct image acquisition cuts out several steps in the image quality testing process and allows for in-the-loop testing with Imatest.

# Greetings From the Path of Totality

If you were lucky enough to travel to the path of totality on Monday, August 21st, you know firsthand how incredible it is to suddenly experience twilight in the middle of the day. The sun transforms into a hole in the sky, casting eerie shades of purple and a 360º sunset on the clouds. Just minutes later, the sun rises over the moon, creating a diamond ring effect. Witnessing this astronomical spectacle in person can’t compare to the photos and descriptions, but the images that I captured in Kearney, Nebraska are truly remarkable! Fewer than 1 in 1,000 people ever have the chance to see the Sun’s atmosphere in their lifetime, and I am extremely grateful to be one of them!

My camera setup. Panasonic GH3 with Canon adapter and 55-250mm Canon lens. I made my own solar filter with film purchased from Spectrum Telescope. I forgot my tripod, so I had to use my gorilla pod.

Composite image from my time-lapse! Each snapshot is about 3 minutes apart.

Composite image of totality! The solar filter was removed during totality and then reapplied for the final phase.

“God’s diamond ring”

The solar corona, consisting of 2-million-degree plasma.

### Timelapse

Each frame was taken 3 seconds apart and play back is 24 frames per second. The solar filter was removed during totality and then reapplied for the final phase.

– Alex Schwartz, Video Production & Mechanical Engineering Intern

# Shooting the Great American Total Solar Eclipse

As predicted by astronomers years in advance, a peculiar cosmic event will occur on the morning of August 21st. Passing directly in front of the sun, the moon will cast a shadow racing across North America at supersonic speeds. From Salem, Oregon to Charleston, South Carolina, the 70 mile wide shadow will darken everything in its path. Outside the path of totality, all of North America will still be able to observe a partial solar eclipse! (more…)

# Using the DarkWorld chart mask

This post is meant to help with the correct setup and operation of the new DarkWorld Chart Mask

The DarkWorld mask pairs with the Imatest 36 patch Dynamic Range Test Chart and frame to block additional light from entering the camera. This allows for more accurate measurements by reducing the flare light coming from the target. Tests with transmissive targets should be performed in a completely dark environment with no ambient lighting apart from the light box.

If you have previously ordered a Dynamic Range Chart, setting up the new DarkWorld chart mask is as easy as 123! Each DarkWorld chart mask comes with six strips of Velcro. If you order the frame and mask together, you will not have to worry about applying these strips yourself.

Step 1: Verify that you have a new DarkWorld chart mask and a 36 patch dynamic range chart with a frame, as well as six strips of Velcro: 2 soft, non adhesive-backed strips and 4 smaller, rough adhesive-backed strips.

Step 2: Place the chart mask in the frame, and apply the 4 rough velcro strips by peeling off their adhesive backing. The Velcro is best placed in the vertical center, on both the left and right side. They should be placed end to end with a small gap to prevent interference when applying and removing the mask.

Step 3: Firmly apply the soft, non adhesive-backed strip to the velcro on the chart mask. That’s it! Now you can ahdere the hanging tabs to the frame or peel them off to remove the Chart mask.

The assembly is now ready for testing with an ITI Lightbox! Simply slide the frame into the rails on the front of the lightbox, and follow the intructions for using Multicharts to measure the dynamic range of your camera system with a single image.

# Artograph LightPad® LX Series – Operational Guide

This post is meant to help with the correct setup and operation of the new Artograph LightPad® LX series.

The classic LightPads, which were operated with an on/off switch, have been discontinued by Autograph. At full brightness, the new LX series outperforms its predecessor with a more neutral, and brighter source of white light. However, the LX model has a dimming feature which utilizes Pulse Width Modulation (PWM). While imperceptible to the human eye, PWM causes flickering which is unsuitable for digital imaging.

LX LightPads must be turned to full brightness to avoid flickering!

### Setting the LightPad® LX to full brightness

• The correct power adapter must be used for proper functionality
• To turn the LightPad on, tap the touch-sensitive power button on the upper right of the front face.
• Holding the power button will cause the brightness level to change.
• If at full brightness, holding the power button will decrease the light level until its lowest setting is reached.
• If at the lowest setting, holding the power button again will increase the light level until maximum brightness is reached.
• If the power button is released at mid-brightness, holding the power button again will cause the light level to continue in the same direction.
• Flickering will occur at every light level below the maximum setting.
• Full brightness can be verified by pointing a digital camera or mobile phone at the device. There should be no apparent banding in the image.
• At lower brightness levels, banding in the image will be apparent in digital images.
• Below full brightness, a buzzing noise can also be heard from the power adapter.
• While you might not be able to see pulsing light with the naked eye, you can actually hear the frequency of the LED driver turning on and off!

Switching Between Brightness Settings on the Artograph LightPad LX 930

# Imatest featured as one of three companies changing the autonomous driving landscape

Imatest was recently featured in Automoblog.net’s article, Three Companies Changing the Autonomous Driving Landscape. Carl Anthony writes:

“With driverless cars, the implication is huge because cameras will play a vital role in the forthcoming autonomous world. In order for autonomy to deliver on its promises of reducing collisions and traffic fatalities, image quality is essential. Imatest takes this into consideration as today’s automotive trends usher us further into autonomy.”

# Imatest Stops Working – Advanced Troubleshooting

### Recovering Mathworks Log Files

Please recover this log file and send to support@imatest.com

The log file name is called “mathworks_<username>.log”. Where <username> is the username of the user that ran the installer. Please see the instructions below to locate the log file depending on your OS.

Windows 10 \ Windows 8 \ Windows 7 \ Windows Vista

The installer log file will be located in the AppData\Local\Temp directory under the user account who ran the installer. The full path, as an example, is:

C:\Users\<username>\AppData\Local\Temp


A shortcut to get to this path is to enter the following into the address bar of File Explorer window, then press Enter:

%tmp%


Windows XP:

The directory is:

C:\Documents and Settings\<username>\Local Settings\Temp\mathworks_<username>.log


Linux:

The log file will be located at the following location:

/tmp/mathworks_<username>.log


Mac OS X:

Follow these steps to retrieve the installer log file on a Mac:

2. Open a Terminal window (you can use Spotlight Search to find Terminal)

3. Copy and paste the following command, and press enter to run it in Terminal. Do not edit the command, run it exactly how it appears below:

cp $TMPDIR/mathworks_$USER.log ~/Desktop


This will create a copy of the installer log file on the desktop. If the command fails, this means the installer log file is not being created. This could indicate that the installer is starting at all, and is thus not able to write the log file. If that is the case, additional information may be able to be obtained from the Console:

Applications – Utilities – Console (or use Spotlight Search to find the Console application)

Use the ‘Clear display’ button to clear out previous console messages. Then try running the installer again and see what is recorded in the console. You can save this information from console. This output may be helpful in addition to the installer log file.

All operating systems:

Forcing the creation of the log file in a specific location:

If the installer is not creating a log file, then you may need to create your own. You can run the installer in command prompt or terminal with a flag to force a log file to be created. You could use a command like the following to do this:

Windows:

/full/path/to/setup.exe -outputfile “C:\path\to\logfile.log”

or

Linux/Mac:

./install -outputfile /path/to/logfile.log

As a note, you can drag the installer into command prompt or terminal and command prompt will automatically populate the path of the installer for you. When defining where the log file will go, make sure it is a directory that you have write permissions. You may need to run command prompt as administrator (Windows) or the installer as sudo (Linux/Mac) in order to do this.

# New Documentation Available for Imatest IT

Imatest is pleased to unveil updated documentation for Imatest IT. The documentation has been updated to include the latest software release (Imatest 4.5), including details for new features, filtering options for preferred languages, and several new Troubleshooting articles. (more…)

# Closing the Loop: Distortion Correction

Imatest’s charts and software allow you to measure the characteristics and parameters of imaging systems. Quite often these measurements simply indicate the limits of system performance and expected image quality.

But some Imatest results let you improve image quality— and subsequent images taken by the same system— by correcting measured aberrations. (more…)

# Reading an Imatest Plot Episode 2: Noise and Dynamic Range

In this video, learn about reading noise plots in Imatest, including how to determine dynamic range (as defined by ISO 15379).