http://www.image-engineering.de What's new . TechNotes . HoTo's en-us 2011 - Image Engineering http://www.image-engineering.de/rss-logo.gif http://www.image-engineering.de http://goo.gl/9nbC6 A version control system is a must-have for every software developer. Read about our preliminary considerations, our experience with Bazaar and take your first steps with a small tutorial. Mon, 20 February 2012 15:11 +0200 http://goo.gl/mt86z Learn more about the method to measure how precise the shutter of your digital camera works. Sat, 11 February 2012 15:16 +0200 http://goo.gl/XTnUu The pixel race in the digital camera industry and for mobile phone imaging modules have made noise reduction a significant part in the signal processing. Depending on the used algorithms and the underlying amount of noise that has to be removed, noise reduction leads to a loss of low contrast fine details, also known as texture loss. Learn more ... Fri, 03 February 2012 19:06 +0200 http://goo.gl/AVDGt An attempt to describe the most used terms around color handling in digital imaging. Not an easy task because everybody knows that it only takes a single color expert to have an argument ... Thu, 02 February 2012 19:16 +0200 http://goo.gl/Ta8p0 Learn more about the two methods to get the OECF (opto electronic conversion function) of a camera. Wed, 01 February 2012 19:50 +0200 http://goo.gl/q6ig3 Learn more about the different charts and their application range. Thu, 27 December 2011 12:25 +0200 http://goo.gl/rECR0 Learn more about the standard for measurement and presentation of specifications for machine vision sensors and cameras. Thu, 15 December 2011 10:35 +0200 http://goo.gl/GLWZG Learn more about the determination of the signal to noise level. Mon, 12 December 2011 09:45 +0200 http://goo.gl/afKvD There are phenomena in the area of physics and especially in optics that cannot be explained by geometry. If light is viewed as particles that follow a straight line and reach a sensor behind a diaphragm. But this is not the case. The light also falls onto areas that should not get light if it would follow the particle theory. Therefore even the best lenses show an Airy circle caused by diffraction and this circle gets bigger the smaller the opening of the diaphragm is. Learn more about DIFFRACTION. Mon, 07 November 2011 08:31 +0200 http://goo.gl/C9bfl In the TechNote ”The concept of noise reduction“ we presented the simple idea behind noise reduction. This idea is based on a seperation of the image in at least two parts (noise and image content). Sometimes it is quite hard to distinguish from noise and image content, especially if you handle with low contrast textures. So if we want to be able to make a statement of how good an algorithm works on that, we have to establish a new numeric quantity, which is called ”kurtosis“. Mon, 31 October 2011 06:01 +0200 http://goo.gl/Cy79U Learn more about how to set up the integrating sphere and the luxmeter for correct measurements. Wed, 19 October 2011 09:41 +0200 http://goo.gl/mbBEQ If you are using a scanner, you set the wished sampling rate of the scan. So if you set it to 300 PPI (pixel per inch), most people assume that they really get 300 PPI. This can happen, but does not have to. To check this, we have to differentiate in different aspects of the sampling rate: CLAIMED sampling rate and OBTAINED sampling rate. Learn more about the SAMPLING RATE. Mon, 10 October 2011 06:29 +0200 http://goo.gl/Gj7t8 Resolition is measured using edges, Siemens stars or other regular structures with increasing frequencies. Take a look at the Spatial Frequency Unit Conversion Chart. Tue, 04 October 2011 07:39 +0200 http://goo.gl/BtDws Compression of video signals is used in order either to reduce the bandwidth of the transmission channel (e.g. satellite TV or network) or to reduce the amount of data to be saved (e.g. DVD or Blu-ray). There are two different kinds of compression – lossless and lossy. Read more about the algorithms for video compression. Wed, 28 September 2011 13:41 +0200 http://goo.gl/XMhWc Based on a request from our customers, our LED-Panel now has an additional mode for determining the impact of a rolling shutter. This mode operates all 10 rows of LEDs simultaneously to see if there is a noticeable time shift in the readout of the camera. Mon, 26 September 2011 08:39 +0200 http://goo.gl/uC1BO "What is the maximum theoretical resolution I am able to measure with the Siemens star chart?" is a commonly asked question. Take a look at a small table that gives the answer for some typical situations. Wed, 21 September 2011 14:07 +0200 http://goo.gl/t9ay4 Nearly all digital cameras use a compression algorithm that is know as "JPEG-Compression". How does this work? The algorithm can be separated in different steps. We only show the steps for the compression, the de-compression works in the opposite order. We show only the most common compression: The lossy compression of 8bit RGB data. "Lossy" means, that the compression will also reduce some of the image content (in opposite to lossless compression). Mon, 19 September 2011 10:07 +0200 http://goo.gl/ZjJy6 The term "light" describes the part of the electromagnetic spectrum visible to the human eye. Similar to the science field of radiometry, photometry studies the measurement of the electromagnetic radiation.There are many corresponding photometric and radiometric quantities using different units of measurement. Read more. Mon, 02 September 2011 19:02 +0200 http://goo.gl/wZhV2 The dynamic range describes the contrast in a scene the digital camera is able to reproduce. It is measured using a gray scale target with a contrast greater than the expected dynamic range of the camera under test. The reported value for the dynamic range can have different units that should not be confused. Noise in images is an unwanted modification of the signal due to physical behavior of the camera and the parts it is made of. Learn more about the units and conversions for Dynamic Range and Noise values. Mon, 29 August 2011 05:51 +0200 http://goo.gl/tc1Hi Modern digital cameras have very powerful noise reduction algorithms implemented in their signal processors. All of them have one thing in common: The algorithm needs to decide “What is noise and what is image content”. Have a look at the concept. Mon, 19 August 2011 08:50 +0200 http://goo.gl/AAYQz Different kinds of glasses cause refraction or dispersion of various intensities. In photographical lenses the the same effect occurs. So it is neccessary to correct these abberations, otherwise you get to see these effects in the images. There are two main types of chromatic aberrations: the LATERAL (or transverse) and the LONGITUDINAL chromatic aberration. Mon, 12 August 2011 06:48 +0200 http://goo.gl/Eciqs Aligning the camera to the test chart without having an optical bench but only a tripod can be quite challenging. There is an easy way to align the camera to the chart perfectly. Mon, 10 August 2011 10:25 +0200 http://goo.gl/Ulw3D In ISO 12233, a slanted edge is used for measuring the Spatial Frequency Response (SFR). When this standard has been developed, this method was know from scanner performance measurement and was adopted for camera measurement. The defined test target has a lot of different structures that can be used for visual inspection and also has slanted edges in horizontal and vertical orientation. Over the years, it could be shown, that there are some issues in using this target. So the standard is under revision right now and we will see a new standard soon. Mon, 01 August 2011 08:25 +0200 http://goo.gl/B2Dkc Generally, the function of rotationally symmetric optical systems is to form an image that is geometrically similar to the object, except for some particular systems, such as fish-eye lenses and eyepieces, where this condition is deliberately not maintained. Ideally, this function is accomplished according to the geometry of perspective projection. Departures from the ideal image geometry are called distortion. Thu, 25 July 2011 07:02 +0200 http://goo.gl/mcAjA In order to describe a color of a not self-luminous source it is important to have detailed knowledge of the illuminant used. The International Commission on Illumination CIE (Commission Internationale de l'Éclairage) have defined a number of spectral power distributions, referred to as CIE standard illuminants, to provide reference spectra for colorimetric issues. Thu, 15 July 2011 07:17 +0200 http://goo.gl/CPrkH The resolution measurement with sinusoidal Siemens stars is applicable to all digital cameras and done within minutes. We have been using this method succesfully for years now for several applications like photography, video, automotive, machine vision and others Thu, 08 July 2011 07:21 +0200 http://goo.gl/1qYDu There are several gray scale charts available: 3,5,7,9,11,13 steps, linear/logarithmic, transparent/reflective, different sizes... So it seems to be difficult to choose the appropriate chart for your needs. But when following some rules it gets much easier to find the right chart. Thu, 07 July 2011 13:30 +0200 http://goo.gl/5xV0r From time to time we do get the question how to clean a test chart. Here is a short instruction for transparent and reflective charts. Tue, 27 June 2011 10:46 +0200 http://goo.gl/FI8Sc As we all know cameras and scanners see colors different than the human eye. Therefore colors are corrected in the camera or scanner software using a 3x3 matrix and sometimes an ICC color profile. Tue, 22 June 2011 11:31 +0200 http://goo.gl/JXKHg The test chart TE268 is designed for resolution and sharpness measurements. Five different structures in the chart allow for a numerical and visual analysis. The chart structures follow the recommendation of ISO standard ISO 12233. Instead of nine Siemens stars there are now twenty-five stars on the chart. This allows the analysis of different image heights and the possibility to get more detailed information of the image area. Sixteen slanted edges are available for resolution and sharpness analysis. Tue, 14 June 2011 10:54 +0200 http://goo.gl/2jEjz Short explanation of COLOR TEMPERATURE, CORRELATED COLOR TEMPERATURE and SPECTRAL DISTRIBUTION. Fri, 10 June 2011 06:03 +0200 http://goo.gl/tak1m Resolution measurement is based on the assumption of linear image data. In most cases the output-data of a camera is in sRGB and has a non-linear OECF (Opto Electronic Conversion Function). So contrast will be amplified / reduced in a non linear way, which causes loss of gray tones and therefore incorrect results. Tue, 07 June 2011 08:49 +0200 http://goo.gl/tUm6p On very important parameter for testing a digital imaging device is the resolution. But there are different ways to express the resolution of a digital camera which are sometimes confusing. Here are the most common units. Fri, 27 May 2011 07:35 +0200 http://goo.gl/1CUUL That a digital camera is able to capture color images is normally nothing worth mentioning. But the color processing in the camera is a very complex topic and nothing trivial. What the manufactures do in the very detail is covered up in silence, but the basic concept is always the same. Fri, 20 May 2011 10:04 +0200 http://goo.gl/R7FNh To receive accurate and repeatable results it is important to check the accuracy of your test chart illumination. Such an illumination needs to fulfill 3 main criteria. Fri, 13 May 2011 06:49 +0200