Image Flare measurement according to ISO 18844_final paper

The ISO 18844 standard that is on the way defines a flare measurement method for a camera lens system similar to the measurement described in the older video standard IEC 61146. In addition it addresses the measurement of flare over the imaging field and also the measurement of devices that do not allow for adjusting the exposure like mobile devices. The paper provides an overview over the sources of “unwanted light” which the standard was originally supposed to address and potential ways to measure these. The current draft version only addresses the standard flare caused by a diffuse white plane mostly within the field of view of the camera. For this kind of flare three different measurements approaches are defined using a single or multiple exposures depending on the level of control the user has over the exposure of the image. Measurements will be presented as well as inter lab comparison issues that came up during the development of the measurement procedure. Introduction No matter if an image is recorded on film or on a semiconductor device there has always been unwanted light that got recorded together with the light coming form the original objects. It is mostly the lens that is responsible for the unwanted light in the images and when the lens can be detached from the camera even nowadays the ISO standard 9358 [1] is used to measure the flare or veiling glare of lenses. As will be seen the terminology around the unwanted light in image capture as well as on the display side is currently a mess and when experts talk to each other a lot of explanation is required describing what they mean. For a lot of cameras especially those in mobile devices like cell phones the lenses cannot be detached without destroying the device. For these cases and for the cases where the impact of the camera body on the flare shall be determined a different procedure than the one described in ISO 9358 is needed. That is why the ISO technical committee 42 (Photography) has decided to create an additional standard (ISO 18844) for measuring flare which they call ‘image flare’. This standard follows a system approach. It defines a test scene that is captured with the specimen and the image is then analyzed. The results include impacts from all parts of the system the environment, the lens, the camera body, and the image processing. All these parts can potentially impact the amount of flare found in an image.