GHL Mitra Owners club

[kien]

Originally Posted by sphelps

I think Keener must has permanently screwed up eyes from watching too many color wheels spin.

I think that a lot more people won't see/notice the disco with these lights. Consider this though, you can see the disco with Radions but there are lots of people who don't ;-)

Also, I think Keener is a screwed up little Sissy Junior Member cry babie

Sub, I hear they're working on the Mitras Pro.

[Delphinus]

Mitras Pro! Well shoot I better wait some more then before pulling this trigger myself.

Can't the disco effect be adjusted by varying the height of the units above the waterline or playing with their position overhead? Or is it pretty much constant no matter what you do - "if you see it, you see it" kind of thing?

[Arok3000]

I played around a bit in my tank, with a different LED albeit, and If I turn off my pumps, then the disco disappears a little. I think pretty much every LED fixture will look great over air shining on the floor, but when you get ripples on the surface, it diffracts the different LED's at separate angles, which causes the disco. At least that's my theory. Possibly some of the disco effect varying between users has to do with the motion at the surface of the water. Less surface ripple could equal less disco.

[subman]

I've had some experience with LEDs (way to much actually lol). When it comes to disco ball effect here is my ratings:
1 mitras (none)
2 radion (small amount)
3 ai sol (visable)
4 ai Vega (very noticeable)

The sol has less because of the lack of colored LEDs. All these were over the same tank on the same rack at some point over last year.

[Reef Pilot]

Originally Posted by Arok3000

I played around a bit in my tank, with a different LED albeit, and If I turn off my pumps, then the disco disappears a little. I think pretty much every LED fixture will look great over air shining on the floor, but when you get ripples on the surface, it diffracts the different LED's at separate angles, which causes the disco. At least that's my theory. Possibly some of the disco effect varying between users has to do with the motion at the surface of the water. Less surface ripple could equal less disco.

It is the surface water ripple that does it with my Radions. When I turn off the pumps, it disappears.

[kien]

Originally Posted by Reef Pilot

It is the surface water ripple that does it with my Radions. When I turn off the pumps, it disappears.

It is indeed the water surface agitation that does it with any point light source. It is called the caustic effect. A caustic or caustic network is the envelope of light rays reflected or refracted by a curved surface or object, or the projection of that envelope of rays on another surface. The caustic is a curve or surface to which each of the light rays is tangent, defining a boundary of an envelope of rays as a curve of concentrated light. In our case the curved surface is the water surface as it ripples and waves. The caustics can be the patches of light or their bright edges. These shapes often have cusp singularities.

Concentration of light, especially sunlight, can burn. The word caustic, in fact, comes from the Greek word for burnt, via the Latin causticus, burning. A common situation where caustics are visible is when light shines on a drinking glass. The glass casts a shadow, but also produces a curved region of bright light. In ideal circumstances (including perfectly parallel rays, as if from a point source at infinity), a nephroid-shaped patch of light can be produced. Rippling caustics are commonly formed when light shines through waves on a body of water.

Another familiar caustic is the rainbow. Scattering of light by raindrops causes different wavelengths of light to be refracted into arcs of differing radius, producing the bow.

T5s do not produce noticeable caustic/shimmering because the light is more enveloping as opposed to being focused like a point source. In essence there is no point source of light from a T5.

LEDs on the other hand typically have several point sources. Each point source producing a caustic. The further apart the individual LEDs are the more pronounced that particular channel's (colour) shimmer/caustic will be. The closer together the individual LEDs are the less pronounced it will be.

Radion LED array:


Mitras LED array:


Kessil 350W LED array:


Caustics on the sandbed from the different LED point sources:




Again, some people will notice it while others will not and at varying degrees of noticeability. If you don't see it or you don't notice it or you're simply not bothered by it then it doesn't really matter what other people see.

[Reef Pilot]

I haven't noticed it for a long time. But when you guys started talking about it here, had to go look at my tank to see it.

I kind of like it though. It only shows up on the sand bottom, and reminds me of snorkeling and seeing the wave shimmers on the sand.

[kien]

Originally Posted by Reef Pilot

I haven't noticed it for a long time.

Ya, I think that eventually you just get used to it. For a long time I ran just halides on my main tank and got so used to the shimmering from the halides that whenever I saw someone's T5 tank it just seemed odd to me.. Then I set up a second tank with strictly T5s over it and over a short period of time I just got used to it and was fine with the lack of shimmer on the T5 tank. Sometimes I think that our knee jerk reaction to something that's different from what we're used to it is to freak out.