Timfish Posted November 2, 2012 Share Posted November 2, 2012 I was taking PAR readings on a tank and thought I'd post this picture showing how fast the light field can change over a very short distance. This is something that's been said before but I'll reitterate anyway but when adding new livestock start low then move high. It is generally easier for corals to deal with lower lighting than they grew under than with higher lighting (although my experience a healthy coral can handle 40% to 50% increase without a problem). (PS. Sensor was moved horizontally to the left about an inch between each of the three measurements. The sensor is about an inch diameter. initially As you can see from the following posts leaving that out caused some confusion.) Link to comment Share on other sites More sharing options...
Robb in Austin Posted November 2, 2012 Share Posted November 2, 2012 I'm a bit confused(but what else is new?!). Did you move the sensor over an inch or down? Link to comment Share on other sites More sharing options...
bige Posted November 2, 2012 Share Posted November 2, 2012 Are those readings an inch apart? Link to comment Share on other sites More sharing options...
+o0zarkawater Posted November 2, 2012 Share Posted November 2, 2012 Link to comment Share on other sites More sharing options...
Robb in Austin Posted November 2, 2012 Share Posted November 2, 2012 Couldn't let it go, could you? Link to comment Share on other sites More sharing options...
+Capt. Obvious Posted November 2, 2012 Share Posted November 2, 2012 Came here to say this...did not leave disappointed Link to comment Share on other sites More sharing options...
bige Posted November 2, 2012 Share Posted November 2, 2012 Couldn't let it go, could you? I believe he could repost same pic after this comment. Link to comment Share on other sites More sharing options...
troypt Posted November 2, 2012 Share Posted November 2, 2012 I couldn't believe how much the par changed by moving the sensor just a small amount when I first got my par meter and tested my tank and other peoples tanks. Troy Link to comment Share on other sites More sharing options...
DerrickH Posted November 2, 2012 Share Posted November 2, 2012 HAHAHAHAHAHA! Literally almost fell out of my chair laughing. Link to comment Share on other sites More sharing options...
victoly Posted November 2, 2012 Share Posted November 2, 2012 Came here to say this...did not leave disappointed came here to see someone say came here to say that. FEELSGOODMAN.JPG. Link to comment Share on other sites More sharing options...
+brian.srock Posted November 2, 2012 Share Posted November 2, 2012 Came here to say this...did not leave disappointed came here to see someone say came here to say that. FEELSGOODMAN.JPG. Came here to see victoly's broken link after he came here to see someone say came here to say that Link to comment Share on other sites More sharing options...
victoly Posted November 2, 2012 Share Posted November 2, 2012 Came here to tell brian.srock that it's an expression not a link. http://ohinternet.com/Feels_good_man Link to comment Share on other sites More sharing options...
DerrickH Posted November 2, 2012 Share Posted November 2, 2012 looks like we have a chan'r among us! Link to comment Share on other sites More sharing options...
nuxx Posted November 2, 2012 Share Posted November 2, 2012 Exactly lol Link to comment Share on other sites More sharing options...
Timfish Posted November 2, 2012 Author Share Posted November 2, 2012 Did you move the sensor over an inch or down? Sensor was moved to the left about one inch for each reading and was kept right at the surface of the water. Link to comment Share on other sites More sharing options...
Robb in Austin Posted November 3, 2012 Share Posted November 3, 2012 So, what kind of fixture was being evaluated? My guess is LED based on moving only 1inch at the same height. Link to comment Share on other sites More sharing options...
Timfish Posted November 3, 2012 Author Share Posted November 3, 2012 No, it was a 250 watt HQI with electronic ballast and Luminmax Elite reflector which has a very good "reflective index" or what ever they call it when it reflects a lot of light. The sensor was about 8" - 10" below the edge of the reflector. Link to comment Share on other sites More sharing options...
Peter Gott Posted November 3, 2012 Share Posted November 3, 2012 That's really useful man, thank you. What motivated you to check this? Are you noticing any measurable difference in your coral in the different zones of PAR? Do you have any colonies that grow throughout the decreasing PAR zone? It'd be neat to compare the same horizontal distances from the source at the same points along a vertical axis but at different depths. I'm curious because that is an awfully big change for just a few inches, and doesn't seem very natural, despite point source lights being touted as being more like sunlight. Even if the way the photons move and their angles of approach are more similar to the sun in a point source light, that kind of variation in intensity across distribution range from the source seems to dramatic on a small level to support the idea that it is in any way comparable. Link to comment Share on other sites More sharing options...
Robb in Austin Posted November 3, 2012 Share Posted November 3, 2012 Yeah, I'm very surprised to see that much of a drop off in a MH. 10"? Sure. 1"? Wow. If you can, maybe check it on the bracing; i.e.; place the sensor on the brace and move it along the width. That way, the height is the same. I've read that varying the height by fractions of an inch can drastically affect the readings. Not saying you weren't at the same height for each reading, but it would take that variable out of the equation. And frankly, I'm surprised you'd get that high a reading under that dirty brace. Link to comment Share on other sites More sharing options...
Timfish Posted November 3, 2012 Author Share Posted November 3, 2012 @ Peter, good questions! First there is the problem of the sensor being to large even though it's only an inch in diameter. Second it does not give a spectral chart. Looking at the attached picture of this two tone birsdnest from the same tank there are areas of the pruple left part that should be gettting less light than the top of the pink righthand protion, why? what would be nice is a sensor that was say 1/8" - 1/4" where it could be placed in between the branchs and measure spectrum and intensity. What started me looking at the lightfield was when I started building LED fixtures. One advantage with LEDs is a lot more of the light is directed compared to MH and T5/PC. Looking at a couple of consumer LED fixtures it was clear there was no ryhme or reason to wattage and light output so I started measuring what the corals were actually getting and boy was I surprised! One thing I learned is some, NOT ALL!, of these corals are not bothered by changes in the light field of 100% to 200% maybe even 300%. An intersting problem I've had with sibling colonies of this birdsnest is at 400 PAR under CW and RB LEDs it looses color (had to add reds to get the color back some) but under 700 - 800 PAR in anoher tank with MH it gets more intense purple. Color temperature of the MH bulbs also affects the coloration @Robb I'm sure there's at least a 10% loss through the glass if not 15 - 20% with the salt. I imagine someone has done a PAR chart of the Lumenmax Elite fixture but I've never bothered to look at what's put out by the fixture rather what the corals are seeing. I was surprised too when I started to look at the light fields in my tanks but similar changes are not uncommon in my other tanks. I was looking at the light field aand since I had the unit stiing on the divider I thought I'd take a quick sequence to show how much the light field can change over a short distance. Since the sensor was at the surface there was a fluctuation of about 10 - 20 PAR and I took the pictures when it was about in the middle of the range. Link to comment Share on other sites More sharing options...
Peter Gott Posted November 3, 2012 Share Posted November 3, 2012 Tim, that picture is perfect! It answers my question visually perfectly; thank you. I love the idea of the PAR probe. A tiny sensor like that could be incredibly useful, for instance comparing the spread and distribution of light from LEDs vs MH within those colonies. I like the direct light effect from the LEDs a lot, but the range of the spectrum put out in LEDs doesn't seem, as you've noted with the colouration problem with the birdsnest, is definitely limited. Even achieving the same overall colour temperature, I've noticed the proportional stregnths of various wavelengths within the overall spectrum of light emitted varies significantly from brand to brand/lighting type to lighting type. Link to comment Share on other sites More sharing options...
Timfish Posted November 3, 2012 Author Share Posted November 3, 2012 The issue wtih spectrum is an intriguing and sometimes frustrating one. The problem is much more of an issue with the chromoprotiens which are responding to different wavelengths of the entire visual spectrum than the florescing protiens which are sensitive just to specific wavelengths in the high UV, blue and low green spectrums. someone who has corals using mostly florescing protiens may not see much of an issue switching to LEDs since white LEDs have a huge hidden lue component. On the other hand for a tank with corals using a lot of chromoprotiens there may be color loss like my birdsnest. I don't know if you've gone to Buildmyled.com but they have 16 different leds to select from and have a really cool tool that shows the spectrum and intensity output. If you are DIY person willing to figure out the math you can use thier website app for other LEDs. Link to comment Share on other sites More sharing options...
ckyuv Posted November 5, 2012 Share Posted November 5, 2012 tim next time you go to aquadome you should come over lol i think i need more light for my tank but wana check before i spend 500 bucks Link to comment Share on other sites More sharing options...
Timfish Posted November 5, 2012 Author Share Posted November 5, 2012 Patrick, why do you think you ned more light? Also how long have your corals been under your current light? They will start adjusting almost immediately but it will take several weeks to acclimate to the existing lightfield. If it has been a month or more and you've seen a loss of color or more extensive brown when you add light it probably will take weeks again for the colors to change. Can you post pictures? Link to comment Share on other sites More sharing options...
ckyuv Posted November 6, 2012 Share Posted November 6, 2012 ths sps just are not growing much. They have been under it for like 6 months now. I have never lost color, infact they always gain lots of blue and the colors always look better than when i get them, just very slow if any growth at all. Ill try and take picks tomorrow, i just got off work and i been here since 6 this morning lol Link to comment Share on other sites More sharing options...
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