LUMINANCES AND VISION RELATED TO DAYLIGHTING

Transcription

1 LUMINANCES AND VISION RELATED TO DAYLIGHTING ALEXIS AGUILAR, URTZA URIARTE, ANTONI ISALGUE, HELENA COCH, RAFAEL SERRA Architecture Energy and Environment Group, School o Architecture o Barcelona, UPC, Barcelona, Spain

2 LUMINANCE BALANCE FORMULATION: GLARE Not sensitive to daylighting + ALTERNATIVE METHODS Physiology o eye ALTERNATIVE FUNCTION (θ) weights luminances in the ield o vision Sensitive to daylighting

3 TABLE 1: SUMMARY OF THE STAGES IN THE PROCESS No. STAGE DESCRIPTION 1 Measuring instruments Fisheye photography + Luminance meter 2 Luminance maps HDR sotware + Calibration system 3 Image processing Visual ield + Solid angles calculation 4 Average luminance calculation o the visual ield Physiology o the eye + Comparative calculations with dierent models 5 Luminance balance o the visual ield Proposal or a calculation model

4 STAGE 1: measuring instruments First instrument: Sigma 4.5 mm F2.8 Camera itted with a circular isheye lens - Result: circular pictures inside the projection rame - Equisolid angle projection (retains the proportions among the solid angles) (The purpose o the photographs taken with this lens is to simulate the visual ield o the human eye) Second instrument: Konica Minolta LS-110 Measurement o luminance - Acceptance angle: 1/3º - Measurement range: rom 0.01 to cd/m2 (Both limits are enough to veriy the measurements taken in this case study, as these margins were not exceeded in any case)

5 STAGE 2: Luminance maps Figure: ive photographs, WebHDR image and WebHDR luminance map.

6 STAGE 3: Image processing Figure: Subdivisions with the same solid angle superimposed on the WebHDR image.

7 STAGE 4: Average luminance calculation o the ield o vision Lmed L i i 0 Where: L i luminance associated with a solid angle; i solid angle o each luminance; 0 solid angle o the ield o vision. cos (θ) unction that weighs the luminance by lowering its value according to the deviation angle with regard to the centre o vision. Clear vision Comortable vision Binocular vision Monocular vision Without vision

8 STAGE 4: Average luminance calculation o the ield o vision Lmed L i i 0 Where: L i luminance associated with a solid angle; i solid angle o each luminance; 0 solid angle o the ield o vision. cos (θ) unction that weighs the luminance by lowering its value according to the deviation angle with regard to the centre o vision. Proposal o other alternative unctions Clear vision Comortable vision Binocular vision Monocular vision Without vision e e 1 c c c Where: deviation angle with regard to the centre o vision; c = 5º. Where: deviation angle with regard to the centre o vision; c = 5º. Where: deviation angle with regard to the centre o vision; c = 5º in the irst case and c = 10º in the second.

9 Function Value Luminances and Vision related to Daylighting STAGE 4: Average luminance calculation o the ield o vision 1.2 Series1 Function (1) c=5º Series2 Function (2) c=5º Series3 Function (3) c=5º (1) e c Series4 Function (4) c=10º Series5 Function (5) (2) e c (3 & 4) c (5) cos angle rom the center in radians Figure: Comparative graph o the 5 weighing unctions.

10 STAGE 5: Luminance balance o the ield o vision G 10log 10 g G is the glare index. DG 2/3( G 14) DG is the daylight glare index. Where: g L a b s L b L s luminance value or the light source; light source solid angle; a,b coeicients; 1.8 and 0.8, respectively; (θ) unction that weighs the luminance; L b luminance value or the background o the light source. The evaluation o the case studies below considers: - L s is a window that provides light rom the outdoors; - L b is associated with the average luminance. cos c Where: The calculation o (θ) is duplicated, using both: - Cosine unction; - Lorentz unction.

11 Figure: Blackboard 1

12 Figure: Blackboard 2

13 Figure: Screen 1

14 Figure: Screen 2

15 TABLE 1: SUMMARY OF THE RESULTS VF L s a (θ) L med G DG Blackboard Cos Lor Blackboard Cos Lor Screen Cos Lor Screen Cos Lor L med (Lor unction): Close to the luminance that predominate in the centre o the vision. More aithul to the visual aculties o the eye.

16 TABLE 1: SUMMARY OF THE RESULTS VF L s a (θ) L med G DG Blackboard Cos Lor Blackboard Cos Lor Screen Cos Lor Screen Cos Lor G and DG indexes: Cosine unction = results are extremely high. Lorentz unction = results more in line with reality.

17 TABLE 1: SUMMARY OF THE RESULTS VF L s a (θ) L med G DG Blackboard Cos Lor Blackboard Cos Lor Screen Cos Lor Screen Cos Lor G and DG indexes when the position o the light source (window) varies. Cosine unction: hardly any variation

18 TABLE 1: SUMMARY OF THE RESULTS VF L s a (θ) L med G DG Blackboard Cos Lor Blackboard Cos Lor Screen Cos Lor Screen Cos Lor G and DG indexes when the position o the light source (window) varies. Lorentz unction: more variation (in line with reality)

19 LUMINANCE BALANCE FORMULATION: GLARE + (θ) weights luminances in the ield o vision ALTERNATIVE FUNCTION Sensitive to: cos c 1. Daylighting 2. Physiology o eye Convincing results 2 reasons 1. Lower glare indexes 2. More sensitive to the window position

20 AKNOWLEDGEMENTS