I'm looking for a website where I can find information about the real performance of leds compared with hmi, fresnel, tungsten, etc. I mean, for example, where I can find the REAL equivalence between one and the other.
Thank you for your time,
#1. "RE: Leds vs Fresnel, Tungsten, etc." | In response to Reply # 0HBB Charter MemberTue 25-Sep-12 07:33 PM
Welcome to Nikonians.
What do you mean by "real performance of leds": Guide Numbers, Watts used, Color Temperature ... ?
What do you mean by "REAL equivalence": Guide Number comparisons, Color Temperature comparisons, Lumens per Watt comparisons ... ?
In my experience, there aren't a lot of specifications available yet. The best source of this information I have found is a local lighting equipment dealer with catalogs for some of the various products.
Sorry I can't offer more.
HBB in Phoenix, Arizona
Nikonian Team Member
Photography is a journey with no conceivable destination.
#2. "RE: Leds vs Fresnel, Tungsten, etc." | In response to Reply # 1
#3. "RE: Leds vs Fresnel, Tungsten, etc." | In response to Reply # 0
I think it may be easier if you describe what you are trying to do.
Tungsten lights produce light with a color temperature typically in the 3200°K range. That's just a little cooler than typical house lighting. Since it's a blackbody source the (color rending index) CRI is 100, so it produced the cleanest light possible at that temperature. Tungsten lights are fairly inexpensive, but produce a lot of heat and only about 20 watts of light per watt consumed.
HMI lights typically produce light with a color temperature in the 5600°K-6500°K similar to daylight. Unlike tungsten, it's not a continuous light source, but it's close. CRI ratings are typically in the 90-95 range. HMI lights are also fairly efficient and can produce 80-100 watts of light per watt consumed. Alas, HMI lighting is expensive, and since the lights typically last well under 1000 hours the expense is recurring. HMI lights have a few other disadvantages as well. Older units tended to be noisy; I don't know if this is an issue any more. Some units can't be turned on immediately after being turned off, others can. And typically you can't dim an HMI source less than about 50% without it turning off entirely. HMI also produces large amounts of UV, but that's typically not a concern for digital still photography.
LED lights are evolving quite quickly. As with fluorescent lights, they come in different color temperatures, with offerings as low as 2700°K (bedroom lighting) to 5600°K (daylight). It used to hard to find high-CRI daylight balanced LED's; even today a typical fixture is more likely to be in the low-to-mid 80's, but I've seen units with claimed ratings as high as 93. Efficiency is as good or slightly better than HMI lighting at 90-100 lumens per watt consumed. A typical unit is rated for over 20,000 hours. Cost falls between the two other options, but prices are dropping quickly.
At the time of this writing, LED lights (and fluorescents) require more surface area than tungsten or HMI lights to produce the same amount of output. So you start out with a slightly softer light. That makes adding modifiers somewhat more difficult -- with some panels the options stop at barndoors. Current units tend to be considerably less powerful than HMI offerings. Most LED offerings are in the 50-100 watt range, where as HMI offerings often start at 200 watts, with 575 watt and 1200 watt lights being fairly commonplace. I've even seen 24000 watt HMI lights offered at over $20,000 just for the ballast.
Fresnel describes a lens placed over the light source. You can buy fresnel lights/lanterns based on all three underlying technologies.
One of the biggest mistakes a photographer can make is to look at the real world and cling to the vain hope that next time his film will somehow bear a closer resemblance to it. - Galen Rowell