For over 15 years, the iQ lab has been measuring the image quality of lenses and gained exceptional experience and expertise in doing so. Prominent photo magazines (e.g., Color Foto; Chip) request this measurement regularly, so we execute the iQ lab - Lens Test daily. We test the lenses in combination with a camera, primarily because the measurement information of a lens alone might be interesting, but nothing a user ever experiences.
The cameras are predefined for every brand (one for every sensor-class) allowing a comparison of every measurement. The iQ lab - Lens Test contains measurements of resolution (center and corners), distortion, chromatic aberration, shading, autofocus accuracy and time-related issues (e.g., autofocus speed) - all characteristics you want to know about a lens.
It is possible to order results of an already executed iQ lab - Lens Test, as well as request a test of a combination chosen by you. We offer two different presentations of the results: A PDF-overview of all numerical results combined with the test images, or a test report of all numerical results which also explains the procedure in detail combined with the test images.
You need more than one measurement, or want to compare a whole bunch of test results? Check out iQ-Data, the database which is filled with all iQ lab - Lens Tests - and grows every day.
If you have further questions or need information on pricing, please contact us.
Image quality measurement
Resolution measurement
One of the most important values when testing a camera lens combination is the resolution. Resolution is the ability of an image capture device to reproduce fine details in the captured scene. It is important to notice that the number of pixels is not the same as the resolution. The number of pixels is a necessary but not sufficient requirement to get to a specific resolution. Optical parts like the lens and the antialiasing filter, as well as image processing, also have a significant impact on the resolution of a camera. And the smaller the pixels get, the higher the influence of optical components on the resulting resolution.
For the iQ lab - Lens Test, the TE268 with 25 sinusoidal Siemens stars, is used with following camera settings:
- ISO100 (where applicable: ISO200) because the noise of the optical system is caused by the camera sensor and not by the lens
- Aperture: Open aperture, two steps closed aperture and at f-stop 5.6 for lenses with a more prominent aperture than f2.0
- Focus: For all images, the manual focus is used and additionally the autofocus at open aperture
All single measurements for the regular lens tests take place in wide angle, standard, and tele focal length.
Lens geometric measurement
Lens distortion can have a different appearance in the image like barrel and pincushion distortion. We report the Lens Geometric Distortion value (LGD) and measure it with the TE251 test chart. The iQ-Analyzer software detects each cross with subpixel accuracy, calculate the ideal grid and calculate the distance between current location and the location on the ideal grid for each cross. We also measure the chromatic aberration so that we can calculate the offset between red and green or blue and green. This calculation is a useful index for chromatic aberration.
For the iQ lab - Lens Test the measurements are executed with ISO 100 and an open aperture. For zoom lenses at three focal lengths – wide angle, geometric middle of the zoom range and tele position.
Shading
All kinds of effects that change the intensity of the field in the image are measured as shading. The TE255 uses a very precise milk glass plate in combination with an integration sphere (LE6). The Shading increases as the focal length decreases.
For the iQ lab - Lens Test we measure the shading of every lens with the following settings:
- ISO: ISO 100 because the noise of the optical system mainly causes by the sensor of the camera and not by the lens.
- Aperture: Open aperture, two steps closed aperture and at f-stop 5.6 for lenses with a more prominent aperture than f2.0
- Focus: For all pictures, we use the focus at infinity to get a homogeneous picture
Autofocus Speed
The test is performed according to ISO 15781 using a LED-Panel in the so-called iQ-AF Box. First, the so-called non-AF-time has to be determined. Therefore the manual focus is used and ten images are generated. With the help of the iQ-Trigger, the camera is released while the LED-Panel is started at the same time.
By counting the lit LEDs in the image after the test, the non-AF-time can be determined. Then the device under test is defocused to infinity and then directed towards the iQ-AF Box. Again ten images are taken, and then the lit LEDs are counted. The difference between the non-AF-time and the shooting lag is the autofocus time. This procedure is done for three focal lengths (wide, standard, tele).
| What we measure | What you get | ||||
|---|---|---|---|---|---|
| tested with | settings | measurement data for | available on iQ data | ||
| Image quality measurement |
 |
ISO 100, open aperture and two steps closed aperture, wide-angle, standard and tele focal length, manual focus for lenses with a bigger aperture than f2.0 also a measurement at f5.6 takes place |
resolution center/corners for 3 focal lengths and 2 apertures | ||
| contrast center/corners for 3 focal lengths and 2 apertures | |||||
| autofocus accuracy wide-, standard-, tele-angle | |||||
| resolution center/corners for 3 focal lengths and f5.6 | |||||
| contrast center/corners for 3 focal lengths and f5.6 | |||||
 |
ISO 100, open aperture, wide-angle, standard- and tele-focal-length | distortion wide-angle (Lens Geometric Distortion) | |||
| distortion standard-angle (Lens Geometric Distortion) | |||||
| distortion tele-angle (Lens Geometric Distortion) | |||||
| chromatic aberration for the 3 focal lengths | |||||
 |
ISO 100, open aperture and two steps closed aperture, wide-angle, standard and tele-focal-length for lenses with a larger aperture than f2.0 also a measurement at f5.6 takes place |
shading wide-angle, open and two steps closed aperture | |||
| shading standard-angle, open and two steps closed aperture | |||||
| shading tele-angle, open and two steps closed aperture | |||||
| visual noise | |||||
| shading wide-, standard-, tele-angle f5.6 | |||||
| Autofocus speed measurement |
 |
ISO 100, wide-angle, standard and tele-focal-length | autofocus speed wide-angle | ||
| autofocus speed standard-angle | |||||
| autofocus speed tele-angle | |||||
iQ lab - Lens Test
All lenses are tested with predefined cameras depending on their purpose. For every brand two cameras, one with an APS-C sensor and one with a full-frame sensor, are preset. So every lens measurement of a brand is comparable to each other.
Products used in this test procedure
Software
Solutions
Measurement devices
Illumination devices
Test charts
