Low K MH's with blue filters?

[bashcraft]

Has anyone tried to use a low kelvin MH bulb, say 4100K with a peice of blue tinted acrylic sheet? Curious as to how much light actually penetrated the acrylic.

BTW, you can buy the tinted acrylic at http://www.thomasregister.com/olc/usplastic/sheet36.htm

Bob

 

[davelin315]

what's the point of that? I understand that we want blue light in our tanks, but that is the actinic that we use, which is at 6700k or something like that. Putting a blue filter on the light is not a substitute, and in fact, will filter out the blue light waves that are there.

 

[DJ88]

Bob,

Are you wanting to use the lower K bulb with the filter for coloration? ie. Use a yellow bulb and then try to filter it so it look pleasing to our eyes? Or create an actinic look? If so it may work. I don't know all of the physics involved but you could do it in my mind. Its a matter of getting a filter that will cover the whole bulb and keep its coloration under high heat and intense light. A lot of regular filters will shift in time allowing more of the undersirable light to pass through. By shifting I mean physically change color. IF you spent the dollars I am sure you can get a filter that you would not have to worry about shifting over time. Colored acrylic IMO wouldn't work over the long run. Due to the intense heat and energy from the bulb. Look how paints fade on a vehicle over time. It usually goes to grey which is a combination of all the colors in the specturm. You would need to buy a very expensive piece of glass designed to filter out by interfering with the light ratehr tahn absorbing it. The same thing is used on HQI bulbs to reduce the UV light getting through. Only difference would be you require a filter to block everything but blue. Not just UV.

One thing that will probably happens is that due to the fact you are blocking such a large part of the light being emitted(as there will be only a very tiny part of the frequency range high enough to create the blue color) you will not get very much light energy out of the MH you have purchased.

If you look at the pic you will see that for a 6700 bulb you get most of the intensity or power at that temperature. It increases to that temp and decreases after. If you place a filter to block everything but say 10,000 degrees you can see there is very little energy being passed through the filter. All the rest is either absorbed or reflected depending on the filter you use. In my opinion you would be best off getting the bulb that provides the light you want(I use Iwasaki's and supplement with Actinics) instead of using a filter. You will get all the power the light is made to supply instead of blocking a large percentage of it.

Dave,

A filter works by absorbing or interfering(The two main types of fitlers) with light waves to allow only the selected color to pass or be seen. Not by blocking the desired color.

Absorption filters absorb the unwanted wavelengths in this case, everything except blue. Some other wavelengths will pass to get the desired frequency or spectrum of frequencies if a combination is required to create the color desired(ie. if you want purple you will need Blue and Red but no Green). Acrylic, as you are looking at Bob, will do this.

Interference filters reflect the unwanted wavelengths to create the desired color. Same principles are involved if a color is desired that requires one or more of the primary colors(Red, Green or Blue), certain frequencies will be reflected back allowing only the ranges of colors needed to pass.

As well the Kelvin rating for blue light is in the range of 10,000 degrees plus. 6700 is a yellow light range.

HTH

[ August 29, 2001: Message edited by: DJ88 ]

 

[chris_h]

Sounds like a waste of electricity and money. Why would you want to do this? If you want pure blue light you could filter a 20K, and it would be much more effecient.

 

[Acropora]

Bob,This idea has been discussed in an article which I believe was in aquarium frontiers.The blue filters/lenses used were the type used for stage lighting.The logic behind this scheme was to use cheap MH bulbs to get the blue of a 10k or better bulb.Yes you would loose some intensity,but the bulbs would last extremely long.The color spectrem of the bulb would change as it got older,but the idea is that with the blue lense this would not matter. I believe the drawback was in the longevity of the filters and the chance of them melting.The filters also acted as a shield to potect the bulbs from water splashes. I'm sorry I don't have a link for this,but you can check the archives of aquarium frontiers online. Anthony

 

[davelin315]

Now why can't I be technically sound like everybody else? Time to get more education....

 

[dieselboy]

I thought about this idea at one time. An option that addresses the UV issue is to use, in conjunction with the Kelvin correcting blue filter, a sheet of Acrylite OP-3, a UV blocking acrylic sheet used primarily to protect items from fading in color (pictures, documents, etc.) The heat issue is something that would have to be considered, however.

IMO, the rationale in using this method is to captialize on the high PAR and efficiency levels of a lower K bulb without having to resort to a complete lighting rebuild. Too much $$$ initially, and that cost increases incrementally over time. The points in doing this would be to, 1) minimize bulb replacement cost, 2)"upgrade" an existing low K lighting system, 3) take advantage of the already very high efficiency level of these lower K bulbs. I am familiar with the two articles written by Harker on this subject, and that's why this intrigues me. The numbers provided seem acceptable for MY application (2X400 Iwasaki DL, 2X'03). The questions are, will it work, and how will it look? This is by no means scientific, but if I look at my tank with blue tinted sunglasses, there is a slight "actinic" effect. Colors "pop" better. Now, if I can see that kind of effect from the side under indirect light through blue sunglasses, it *might* mean that the effect of the K-correcting blue filter *below* the lamps would have an even more dramatic effect under more direct light....just a thought....

 

[bashcraft]

The reason I want to do this is, I have an open top tank with pendants and can't supplement with actinics. I like the open top but not the color of the bulbs I've tried.

I'm currently using 12kK Sunbursts, and to tell you the truth, they SUCK. I'm on my third pair in just a little over a year. I can't find 2 of them that are the same color and they've all lost most of their intensity in the first couple months.

The pendants have a clear acrylic sheild on them now. I was thinking of replacing it with a blue sheild and running some 5500k bulbs that I already have.

Bob

 

[DJ88]

Bob,

I can see exactly why you are interested in doing this. Understandable. You are going through bulbs like candy.

Personally, I'd look around for a glass filter. One that will handle the heat fom the bulbs. If possible do look for a filter that is an interference style. It may be a bit more expensive but if it works in the long run you will be using only the one bulb per year. Tho now that I think about it you could test your idea with a cheaper glass or acrylic to test it first. See how it looks and decide then if you want to pay the money for a decent filter.

It does sound like a good idea to me..

Go for it and let us know how it works. Try it with a piece of acrylic. Just make sure the color you use is close to waht you want. Being that you are using pendants it will be easy to cover the bulb completely.

You may start a new trend.

Dave,

I have done lots of training and schooling working with radio frequencies. All types. Part of that schooling included the lower end of the spectrum. Which is light.

Now by looking at your profile if we were to meet say in a legal setting you would probably prosecute my a$$..

 

[jdeets]

I'd think that it wouldn't work very well. As mentioned in prior posts, a blue filter will eliminate the longer wavelengths of light from the spectrum. With a lower K rated bulb, most of the spectrum is longer of longer wavelengths, below the blue range. If you filter out what's there and only let the blue through (the effect of using the blue filter), then you'll end up with very little light energy actually getting through the filter. Why? Because there was no blue light there to begin with, and the blue filter will only let blue light through.

I'd be curious what kind of PAR rating you'd get with that setup. My guess is that if you put a blue filter on a lower K light, the PAR actually passing through the filter will be drastically less than the PAR of the unfiltered bulb.

Basically, you can't use a blue filter to create blue light when there wasn't any blue light there to begin with.

I'd also be interested in hearing Galleon's thoughts on this thread, because he'd know a little more of the physics behind all this.

 

[Mustang]

There is a very good article out there on this exact subject if i Can find it I will post it
One of the point I remember was that even with the filter the 65K bulb put out more Par than a 10kAnd were a lot cheaper. It gave the tank the blue color that we seem to like better

 

[Nathan1]

Well, here I am again.

I've done it. Used ROSCO theatre lighting gel acetate filters.

End diagnosis: it's not worth it. Just spend the money on some good 10K Ushio's.

Reason: The filter gels bleach after a while. On my 175W 4300K Venture bulb the gels only lasted 3 months before I noticed a significant colour change in the gel. The light output is sevelely attenuated. My mind kept telling me to buy a proper bulb.

After I listened to myself I bought a proper bulb and I was thrilled with the results.

I'll never use the filter gel method again.

-Nathan

 

[DJ88]

James,

I do agree with you about losing power. I just think it is an interesting idea to solve Bob's predicament. If he is willing to accept the loss in power output it may let him have the desired soothing color he is looking for.

There will be some light in that upper frequency range of 10000 kelvins. To make a bulb that emitted only say 6500 would be very costly. In most cases the bulbs just emit such a high amount of one specific frequency (general frequency actually) that the one frequency overpowers the others. I'll go into more detail if you want.

All theose years of engineering and electronics may as well be used for something.

I know that by placing the filter on you will be decreasing the power outputted by the bulb. Significantly. In any filtering process the power blocked will be lost. If you look at the diagram I made up you will see that in relation to the amount of light emitted at a lower Kelvin you can see there is a significant difference. If I was to go into detail and make up a snazzy diagram showing the actual levels and scales we coudl do the math and figure out the % loss of a filtering of this "theoretical" bulb. Or even an actual Iwasaki bulb for that matter.

In effect by placing a blue filter over the bulb you are making a "Band Pass Filter" this filter blocks everything except the frequencies desired. In doing this in any RF function the power you block is lost. It is usually dissipated in the form of heat. No energy can just be dissipated. Energy in = Energy out. Easy as that. In the case of light it will change mostly into heat. This heat will have to go somewhere. If acrylic lenses are used they will melt. If high grade photographic lenses are used you will minimise the absorption of this heat into the glass due to the fact the filter is reflecting the undersireable frequencies instead of absorbing them as the acrylic would do. You would definately need vents in the pendant casing tho. If you look at this pic I have added in waht the filter(glass) will do. The blue line is a rough hand draw version of a band pass filter.

Another solution to Bob's situation could be creating a pendant system for some actinic bulbs. Using say rain gutter material it could be done. If it is neatly fabricated it could look pretty sharp.

[ August 31, 2001: Message edited by: DJ88 ]

 

[DJ88]

James,

I gotta ask this. I have been curious.. Maybe I am in a pissy mood but, hey I had to ask....

He does know his stuff. but why wait to see what galleon has to say on this? I am curious....

I have been working with RF for years as a technician and provided a good explanation. All based on real time, real world experiences, real world knowledge and learning. I have one diploma in electronic engineering specializing in acoustics and am currently pursuing second in Telecommunications and wireless communications. My last certificate in electronics was specializing in digital signal processing and various RF(radio frequency) applications. Was what I attempted to explain not enough?

Just to clarify there will be light in the correct kelvin range to pass through the filter. If there wasn't, red, blue, purple, yellow or whatever filters on a bulb would not let those colors pass(appear visible) even tho they are desired. With the exception of very very precisely made bulbs or lamps designed to emit a very precise light wave there will be all frequencies of light emitted by the bulb. Just at varying levels. We aren't able to see them as the materials in the bulb only show a certain range of color with any intensity. If you were to measure the various ratings with the bulbs we get over the counter you will see some of all frequencies. A 6500 kelvin bulb does not put out only 6500 degrees temp light. That is the most intense for that bulb. If you filter this out you will be able to see the other ranges. Or measure it with a meter. UV and Infrared are also emitted. Why do you think HQI bulbs require a filter for proper usage. The emit such a high concentration of UV rays they require it. You can't see them. But they are there. They are too high in the spectrum for us to see them. Infrared are too low. THey are there too. The heat you feel from your bulbs is partially due to Infrared. Another part is due to the resistance of the materials used to create the filament in the bulb.

Basically there is no perfect filters. No filter only allows one specific frequency to pass through. There is fall-off. If you look on my diagrams you will see that the light emitted peaks at a certain kelvin. But is sloped downwards from that point or falls off. Other frequencies do get through, it is just they are of such a low intensity(strength) that the get masked by the main frequency desired. Or in the case of a MH the frequency that the materials(gasses, metals) used in the construction of the bulb create. And the wonderful thing about bulbs are that they are in effect a filter. They block out the majority of undesired frequencies and allow most of the energy supplied to be created as a band of desired light. approx 6500 kelvin for an Iwasaki.

[ August 31, 2001: Message edited by: DJ88 ]

[ August 31, 2001: Message edited by: DJ88 ]

 

[jdeets]

Nothing against you or your explanation from a physics standpoint, DJ88. I think it was right on. However, I don't agree with your advice and the fact that you changed your position in the middle of the thread is troubling to me.

IMO, more opinions and insights are better than fewer. I admit that sometimes it is laborious to read galleon's posts when they get a little technical, but I do value his opinions and he is probably just as well-read in the area of lighting for marine systems as anyone on the board.

The diagrams you posted certainly do tell me that using a blue filter with lower kelvin bulbs won't work well. The diagram even for the 6500K bulbs shows HUGE intensity at the 6500K range, although there is no scale to determine how that intensity is measured. By the time you get to the blue part of the spectrum, it appears that the intensity in that color range is about 10% of the intensity of the lower ranges. If the blue filter is going to mainly let light through in the blue spectrum, then the most intense wavelengths are going to be filtered out.

It looks to me that trying to do this will be counterproductive at best. Blocking so much of the more intense light spectrum might cause so much PAR to be lost that the lights are ineffective.

First and foremost in this hobby should be the health and well-being of the livestock. Aesthetics comes somewhere after that. He might not like the look of the more yellow light, but by blocking most of the PAR with a filter to make the color more pleasing, he's going to be compromising the health and well-being of his livestock.

You haven't provided any information regarding what percentage of PAR is going to be lost in doing this. Your initial advice was that this wouldn't work well and that he should just buy bulbs of the desired color spectrum. I thought that was sound advice. However, in a later post you said it sounds like a good idea, and to try it and see what happens. Why did it become a good idea in the later post? Because Bob doesn't want to shell out the $$$ for different bulbs?

Others have tried this and said it didn't work. Before he goes down that road, my advice would be for him to look for some information regarding the intensity of the light that will be let through. I mean, why should he be running MH if his livestock isn't getting any more PAR than they'd get with NO flourescents?

IMO, Bob should get a little more empirical data, and also to try to get his hands on some more anecdotal evidence from people who have tried this, before he tries it himself. Beyond that, my advice would be to get some 10000K+ Bluelines.

No flame intended, JMHO. You asked so I gave you an honest answer.

 

[Anonymous]

Jdeets,
thanks for sending me your concerns on this thread. I do think Darren gave an excellent explanation overall (BTW, DJ, I sent you a PM). Re: lost PAR. Its impossible to quantify such a statistic for filters in general. It will likely differ very highly for each individual filter selection. You are certainly going to lose intensity. How much? again, varies highly for the individual filter. Some various kinds may be tested (did someone say "Nathan"?

), placed over a bulb with a set of givens as to which irradiance and perhaps even output is known prior to the filter's installation, then make measurements on pertainent factors (output, irradiance, PAR...) and calculate the delta values for each. Until definitive work as been done with gels and the like, I'm reluctant to, in fact, I'm refusing to take any biased stance on this issue. I just don't know for sure. However, I will tell you, that like Nathan, I have used the acetate gel filters for display/aesthetic purposes on aquaria other than the reef variety. They don't last.

[ August 31, 2001: Message edited by: galleon ]

 

[shadetree]

A lot of this discussion is above me at the moment but here is a picture of two frag vats at a friends house, both lit with the same kind of bulb, and look at the difference in brightness. The blue filter took a lot away. He did not like the set up and removed it.

Scott