Joined: Jan 30, 2007 Posts: 2219 Location: HYD-is-good
Posted: Mon Sep 16, 2013 8:02 pm Post subject: Re: lux meter / PAR meter using smartphones
Atleast I dint know. And a drawback of not being Android user!
But I was looking around for the filters to get a simple PAR meter, but none spare in centimetres size.
Moreover you need a standard PAR meter to caliberate your camera, all the more not all cams are same so wonder how a simple coded app will be anywhere accurate.
Congrats on your first post
Posted: Mon Sep 16, 2013 8:14 pm Post subject: Re: lux meter / PAR meter using smartphones
It doesn't need camera, it uses light ambient sensor in the phone and gives you the intensity of light in terms of lux . This is more sensitive and the reading 0 starts for a low but visible light (you can only experience it, difficult to point it out precisely. But these are sensors can get you readings if you take it closer to the light source. I'm not sure about the max intensity you can expose your mobile to.
Posted: Wed Sep 18, 2013 8:36 am Post subject: Re: lux meter / PAR meter using smartphones
@superbsite hey you can YouTube videos for that app for demo. There's nothing much to learn in that app. Its simple to use. I don't know about the calibration part.I never really used any hardware meters before. If somebody comes up with a reference chart or something like that using that app, it would be much appreciated.
I'm gonna use it to experiment and find out optimum light intensity for emersed setups
Posted: Wed Sep 18, 2013 12:35 pm Post subject: Re: lux meter / PAR meter using smartphones
This may help.
Aqua Design? > ?
Plant life has been evolving under the sun for millions of years. It follows,therefore,that natural sunlight is the perfect form of illumination for aquarium plants. Natural daylight,however,is difficult to control as its intensity varies from day to day depending on the season,cloud cover,time of day and degree of atmospheric pollution,etc. And without any control over the amount of light the aquarium
receives,blooms of unwelcome algae may develop in excessively bright conditions. It is necessary,therefore,to use artificial forms of light in aquariums. Fortunately,over the past 20 years or so,many new forms of lighting have become available that lend themselves to aquarium use. By carefully controlling the quality,intensity and duration of the light,it is possible to achieve perfect aquarium plant growth using purely artificial light sources.
Quality of light
Visible light forms only a narrow segment of total electromagnetic radiation,which ranges from extremely short cosmic rays to long radio waves and beyond. The familiar visible spectrum of violet to red light occupies a portion of wavelengths from 380 to 780 nanometers. (A nanometer,usually abbreviated to nm,is a billionth part of a metre). Just as the human eye varies in its sensitivity to different wavelengths,so chlorophyll in plants also absorbs the spectral components of light to varying degrees. The absorption spectrum for chlorophyll shows noticeable peaks in the violet-blue (380-480nm) and orange-red(600-680nm) regions,which also mark - as you would expect - peaks in photosynthetic activity. (That plants reflect most of the green light and absorb relatively little is clear from their apparent green color to our eyes.) for plants to prosper under artificial light it follows,therefore,that the most effective light sources will be those that produce a large portion of their light in the blue and orange-red regions of the visible spectrum.
Intensity of light
it is very difficult to judge the brightness of a light source;it all depends on the background level of illumination. In pitch darkness a car headlamp,for example,may seem dazzling,whereas in full daylight it appears very dim. To understand the way brightness is calibrated we must introduce two units of measurement. The amount of light produced by a light source is measured in units known as lumens. (The number of lumens produced per watt of power applied to a lamp is a measure of its efficiency. In general terms, an incandescent lamp is less efficient than a fluorescent tube because a greater portion of the power applied to the former is converted into heat rather than light.) The amount of light reaching a surface is measured in lux,which is equivalent to lumens per square metre. Lux is measured with luxmeter or lightmeter. (A standard photographic exposure meter can be used to measure lux by converting the diaphragm and exposure times.)
Plants vary widely in their light intensity requirements. Aquatic plants growing in the deep shade of a forest pool flourish at far lower light levels than those adapted to live in the shallows of streams open to the sky. And land plants that live in the full glare of the sun absorb surprisingly high lux levels. The table lists the lux requirements of a representative selection of aquarium plants,plus some land plants for comparison.
Light requirements of selected aquarium plants :
1500+ lux/Very bright
Succulents 9,000-14,000 lux
Young trees 10,000-15,000 lux
Cereals 50,000-60,000 lux
Fortunately,most aquarium plants have similar requirements and/or are adaptable within a specific range. Thus,it is usually possible to grow different species with varying lighting needs together in the same aquarium.
The duration of light
Tropical plants are known as 'short day plants'. This is because in the areas of the world close to the equator,day and night are divided approximately into two periods of twelve hours each. Of the twelve hours that the sun shines in a tropical day,sunset and sunrise occupy a period of one hour each. This leaves ten hours of intense light. This period,the so-called 'photoperiod',is the length of time you should leave the lights on in the aquarium for tropical plants to 'feel at home'.
Also remember,however,that the period of darkness is even more critical than the photoperiod. during darkness,respiration is at its highest level. Oxygen is absorbed and carbon dioxide released. The sugar stored in the cells is oxidized according to the following equation:
C6H12O6 + 6O2 ---> 6CO2 + 6H2O + 674 calorie
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