Exposure (photography)

In photography, exposure is the amount of light per unit area (the 's illuminance times the exposure time) reaching a frame of photographic film or the surface of an electronic , as determined by shutter speed, lens F-number, and scene luminance. Exposure is measured in lux seconds, and can be computed from exposure value (EV) and scene luminance in a specified region. An "exposure" is a single shutter cycle. For example, a long exposure refers to a single, long shutter cycle to gather enough dim light, whereas a multiple exposure involves a series of shutter cycles, effectively layering a series of photographs in one image. The accumulated photometric exposure (Hv) is the same so long as the total exposure time is the same. Definitions Radiant exposure Radiant exposure of a surface, denoted He ("e" for "energetic", to avoid confusion with photometric quantities) and measured in , is given by :H_\mathrm{e} = E_\mathrm{e}t, where *Ee is the irradiance

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1ère année: bases nécessaires à la représentation informatique 2D (3D). Passage d'un à plusieurs logiciels: compétence de choisir les outils adéquats en 2D et en 3D. Mise en relation des outils de CAO et DIM: regard critique et aptitude à choisir les méthodes nécessaires au résultat recherché.

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A 500 x 500 Dual-Gate SPAD Imager With 100% Temporal Aperture and 1 ns Minimum Gate Length for FLIM and Phasor Imaging Applications

Andrei Ardelean, Claudio Bruschini, Edoardo Charbon, Paul Mos, Arin Can Ülkü, Michael Alan Wayne

In this article, we report on SwissSPAD3 (SS3), a 500 x 500 pixel single-photon avalanche diode (SPAD) array, fabricated in 0.18-mu m CMOS technology. In this sensor, we introduce a novel dual-gate architecture with two contiguous temporal windows, or gates, guaranteed by the circuit architecture to be nonoverlapping and covering the totality of the sensor's exposure period. The gates can be adjusted with a temporal resolution of 17.9 ps, and the minimum measured gate width is 0.99 ns; to our knowledge, the shortest reported to date among large-format SPAD imagers. In the dual-channel mode, the burst frame rate is 49.8 and 97.7 kframes/s in the single-channel mode. A 2690-MB/s PCI express (PCIe) interface has been added to the data acquisition framework, enabling continuous operation at approximately 44 and 88 kframes/s. Due to optimizations of the gate-signal tree, we achieved a significant reduction to gate skew and gate width variation, which is negligible with respect to the SPAD temporal jitter. These improvements, along with sub-10-cps dark count rate (DCR) per pixel and 50% maximum photon detection probability (PDP), result in a sensor particularly well suited for fast acquisition fluorescence lifetime imaging microscopy (FLIM) experiments, for which we demonstrate reduced dispersion versus a single-gated sensor.

IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC2022

Robust Multi-View Change Detection

Jérôme Berclaz, François Fleuret, Pascal Fua, Alessandro Lanza

We present a multi-view change detection approach aimed at being robust with respect to common “disturbance factors” yielding image changes in realworld applications. Disturbance factors causing “slow” or “fast-and-global” image variations, such as light changes and dynamic adjustments of camera parameters (e.g. auto-exposure and auto-gain control), are dealt with by a proper single-view change detector run independently on each view. The computed change masks are then fused into a “synergy mask” defined into a common virtual top-view, so as to detect and filter-out “fast-and-local” image changes due to physical points lying on the ground surface (e.g. shadows cast by moving objects and light spots hitting the ground surface).

2007

Pro-oxidant effects of nano-TiO2 on Chlamydomonas reinhardtii during short-term exposure

Paul Bowen, Amarnath Jayaprakash, Volodymyr Koman, Olivier Martin, Lionel André Maurizi, Christian Santschi, Nadia Rachel Von Moos

This study sheds light on the short-term dynamics of pro-oxidant processes related to the exposure of C. reinhardtii microalgae to nano-TiO2 using (a) conventional fluorescence probes for cellular pro-oxidant process and (b) a recently developed cytochrome c biosensor for the continuous quantification of extracellular H2O2. The main aims are to investigate nano-TiO2 toxicity and the modifying factors thereof based on the paradigm of oxidative stress and to explore the utility of extracellular H2O2 as a potential biomarker of the observed cellular responses. This is the first study to provide continuous quantitative data on abiotic and biotic nano-TiO2-driven H2O2 generation to systematically investigate the link between extracellular and cellular pro-oxidant responses. Acute exposures of 1 h were performed in two different exposure media (MOPS and lake water), with nominal particle concentrations from 10 mg L-1 to 200 mg L-1, with and without UV pre-illumination. Abiotic and biotic extracellular H2O2 were continuously measured with the biosensor and complemented with endpoints for abiotic ROS (H2DCF-DA), oxidative stress (CellROX (R) Green) and damage (propidium iodide) measured by flow cytometry at the beginning and end of exposure. Results showed that nano-TiO2 suspensions generated ROS under UV light (abiotic origin) and promoted ROS accumulation in C. reinhardtii (biotic origin). However, extracellular and intracellular pro-oxidant processes differed. Hence, extracellular H2O2 cannot per se serve as a predictor of cellular oxidative stress or damage. The main predictors best describing the cellular responses included "exposure medium", "exposure time", "UV treatment" as well as "exposure concentration".

Royal Soc Chemistry2016

Photography

Photography is the art, application, and practice of creating s by recording light, either electronically by means of an , or chemically by means of a light-sensitive material such as photographic fi

Photographic film

Photographic film is a strip or sheet of transparent film base coated on one side with a gelatin emulsion containing microscopically small light-sensitive silver halide crystals. The sizes and othe

F-number

An f-number is a measure of the light-gathering ability of any optical system like a camera lens or even the human eye. It is calculated by dividing the system's focal length by the diameter of the