post 6 from this page: https://photography-on-the.net/forum/showthread.php?t=261340
I did the calculations for someone else and the numbers are pretty scary.
Let's say the 430EX is 50 watt-seconds (realistically it is closer to 100 w/s, just that monolight owners won't admit it). Anyway take it as 50WS.
A watt-second is how much power the light would consume, if spread out over one second. So, a 50W light bulb turned on for one second would generate 50 w/s. Let's take an inefficient light source generating 10 lumens per watt. So that's 500 lumens, not unrealistic for a home lightbulb at 50W. Now we've got 500 lumen-seconds.
Problem is a flash cannot stay on for one second as many exposures are much faster than that. Flashguns go off around 1/1000th of a second... you can imagine where this is heading to have so much power discharged in a tiny fraction of a second. Condense your 500 lumen-seconds into 1/1000th of a second. Yes, that is half a million lumens when the 430EX fires at full power.
The reason why 'hot lights' work is that you use long shutter speeds. You would only need a 500 lumen light source IF you could expose for one second. If your exposure is completely driven by the flash duration, then you have to deliver that amount of power in that tiny little window of opportunity.
I did some tests with a known 1K lumen light source, exposed for 1/200 f/8 ISO 400 in a pitch black room. Hardly anything showed up. I then did it again with the 430EX at 1/16 power (manual, not E-TTL2) and the whole room lit up bright as day. So it pretty much confirms that the flash is a few orders of magnitude more powerful than hot lights, but of course, the duration is MUCH shorter.
Your LED concept would get you a macro ringlight, but not a macro ringFLASH. There is no reason why it cannot be done given adequate thermal management and/or a very reduced duty cycle to allow the heat time to dissipate.
A cheaper solution is to take two flourescents and stack 'em on a desk.. well that's if your subject does not run away
My solution? ST-E2 and 430EX.
you will also see problems with the lights not giving off a full spectrum of light. Take a look at the first graphic on this page: http://intiridesigns.com/articles/color.php
notice the yellow line which is daylight, the same light that a flash tries to emulate. Also notice the LED light's output, there are spikes and valleys. There's no way to know if those shop lights would show the same, better or worse spikes and valleys.
I'm not trying to say that the lights you posted won't work for what you need them for (by the way, why do you need them?) but you need to be aware of their limitations as well as the benefits of a full spectrum flash. You can pick up a solid flash for a hundred bucks that will put out more light (for a shorter duration) than those shop lights.
PSA: The above post may contain sarcasm, reply at your own risk | Not in gear database: Auto Sears 50mm 2.0 / 3x CL-360, Nikon SB-28, SunPak auto 322 D, Minolta 20
