Hi Sanjeevkumar,

Regarding the position index, you can check the following papers on how to calculate this parameter:

-M. Luckiesh and S. K. Guth, "Brightness in visual field at borderline between comfort and discomfort (BCD)", Illuminating engineering, 1949.

-Wonwoo Kim, Hyunjoo Han, and Jeong Tai Kim, "The position index of a glare source at the borderline between comfort and discomfort (BCD) in the whole visual field", Building and Environment, 44(5):1017–1023, 2009.

However, it can be defined after glare source detection.

If you do not have access to a digital camera, you probably need to do a bunch of measurements throughout the whole visual field and then follow the same rules used by Evalglare for glare source detection, e.g. identifying pixels with a luminance value five times higher than the average task-zone luminance as a glare source.

For calculating the DGI, you can also have a look at the original paper:

P. Chauvel, J.B. Collins, R. Dogniaux, J. Longmore, Glare from Windows: Current Views of the Problem, Lighting Research & Technology, vol. 14, (1982), pp. 31–46 no. 1.

I hope this is helpful.

Zahra

Thank you Zahra Hamedani

I gone through many references as you mentioned but here i have one dought we have a luminance meter and camera but we don't have fish-eye lens is it possible to evaluate glare using normal lens camera. any material means is more helpful.

Thanks for your response

Hi Sanjeevkumar,

Yes, it is possible to use images acquired from a normal lens camera for glare assessments, but you need to be aware of some issues. Please check the following links and let me know if you had any questions regarding the calibration process.

https://radiance-online.org//pipermail/radiance-general/2012-February/008353.html

http://web.mit.edu/sustainabledesignlab/projects/TeachingResources/HDR_II_Photosphere.pdf

Zahra

Hi Zahra Hamedani

Thank you

Ya sure once i'll start and let you know thanks for your support and information

how to take vertical illuminance means a position where we use the camera in the same place or near the window we have to find vertical illuminance using lux meter. and camera settings is taken care as per the second link what I got from your side is okay to create an HDR image.

Please do needful

Hi

Vertical illuminance should be measured at the lens of the camera on a vertical plane. As the camera is recording the LDR images, you should record the illuminance values at the beginning and end of each sequence. Then use the average value (the average of two measurements at the beginning and end) as your measured illuminance.

If you are working under daylight conditions, it is recommended to automate the LDR image recording. Let me know if you require further information.

Regards,

Zahra

yes I got it I want to find the daylight glare for an indoor environment to know the visual comfort and also we are using the canon-750d camera to take images. I am considering 5frames -2 to +2 and the camera is having a touch screen capacity to take images. if I have to automate the camera to take images for different exposure means what I have to do if any tutorial means helps a lot.

the software to convert hdr images for glare analysis is mac based one how can I do in windows based software.

also the links are given in that tutorial also not available it showing an error. anyway now I am able to generate the hdr image means how to find the calibrated values for my camera.

Any best suitable method means helps a lot.

Hi,

1) Five frames might not be enough. In your set of LDR images, the brightest one, shouldn't have underlit area and the darkest one, shouldn't have overlit area.

2) For automated image capture, you can use “qDslrDashboard” for windows. It can be downloaded from http://dslrdashboard.info. There is a tutorial on the website.

3) Instead of photosphere, you can use hdrgen. Check radiance website https://radiance-online.org/

4) For the calibration process, check the following articles:

HANSEN, P. et al. HDR Images for Glare Evaluation: Comparison Between Dslr Cameras, An Absolute Calibrated Luminance Camera and A Spot Luminance Meter

Clotilde Pierson et al. - Luminance maps from high dynamic range imaging: calibrations and adjustments for visual comfort assessment

Regards,

Zahra

Thank you,

I'll go through it and if any query I'll come back to you now I am able to get one software aftabalpha and hdr scope there is some issue but time being it is okay.