I really enjoyed those illustrations too. Made it easily understood to a non techy person.
Cool, I'm glad. That's what I was aiming for. Was quite fun to do. If we all talked in terms of PAR instead of watts, it would eliminate a lot of variables in diagnosing setups. I do wish the meters themselves were cheaper, I know that is the main barrier for hobbyists.
That is some really great PAR data for power saver bulbs.
I also was a little surprised at how useful they could be.
I plotted the data on log log paper to see what kind of relationships are there. It looks like the light intensity drops a little faster than if it were just an inverse square drop off. I'm not at all sure why that would be.
Raising or lowering the reflector over a small tank like that is going to change the light distribution and also reflect off the side glass differently. That divergence from the inverse square relationship basically indicates how the reflector shape and material comes into play. Additionally, the water itself absorbs the light in addition to the inverse square law, no?
Also the relationship between intensity and bulb wattage isn't quite linear, with the intensity increasing a bit faster with power than if it were linear. That is understandable because there is more area radiating light with the higher wattage bulbs and less dark area of tube. Also, at equal distances between the light and the sensor, the vertical mounted bulb gives about 55% more intensity than the horizontal mounted bulb. That is probably from less restrike.
I also think that restrike is a huge factor in limiting the radiating light in the horizontal configuration. But that's what is great about using the PAR meter... if you reconfigure your lighting, you can see in realtime what the effect is going to be in terms of photosynthetic energy for the plants. That 55% increase is not very noticeable to the naked eye, yet it is there.
The data also has a lot of practical use for guesstimating how many of what wattage bulbs will give a 100 micromol (for example) intensity at the substrate for any given tank size.
Yes, a virtual PAR meter of sorts. The thought had crossed my mind... but without accounting for reflector types, light distribution variations, water depth, turbidity, and brand of bulb, you're still back to not knowing exactly how my photosynthetic energy you really have.
Thank you very much for doing this.
Any way we could get shots of the reflectors used in your tests? ie: The one for the vertically mounted bulb and the horizontally mounted bulb.
Sure, however, there's not much left to the imagination concerning those two fixtures shown in the diagrams. The metal dish reflector is the exact same material on the inside. The desk lamp is simply painted white on the inside. However, I can photograph the interiors when I get back in town.
I think this is one of the most helpful posts I've read on here. I read it before lights on on my 2.5g tank, that's had somewhat of a halt on the HC growth, and the leaves were starting to get a little pale. I raised the light 1.5" before lights on and it looks nice and green like it should again!
I have no doubt that raising your lights caused a visual difference to you, but the real question is "what was your photosynthetic energy before you raised the fixture, and what was it after?" Such a change in the lighting would take a bit of time to see the results in terms of the growth of your plants - especially with non-co2 - probably on the order of weeks. By raising the light a couple of inches, you are effectively reducing the photosynthetic energy being supplied to the plants... that will, in turn, reduce the demand for nutrients. If there is less demand for nutrients, then your substrate may have a better chance at providing them through normal bio-chemical reactions.
By using this PAR meter, the idea here is to remove the notion of "how much light/watts do I need?" Instead, we focus on how much photosynthetic energy (PAR) is being supplied to the plants. This is not something you can determine just by looking at the setup, or knowing how many watts you have. Maybe you were overdriving the bio-chemical system in your tank, maybe not. A PAR reading would give us a better answer.
If you were already in a good range, then maybe your paling HC is because of a lack of nutrients overall. Do you see how this conversation would be a lot different if you said "I am providing X amount of photosynthetic energy to my plants, but the HC hasn't been doing well." ? Then we could immediately know if your lighting was at fault or not, and then move on to other factors.
yeah I must of not seen that drop checker..lol..I was so focused on checking out those foreground plants...lol, will the tanks by be small...I still love the meaning behind them, it's nice to know something like that is possible
Yes, I understand, totally :-)