Tungsten light with CTB gel / HMI difference

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videomaniac

Member
...anyone know the difference between using a tungsten light with a CTB gel as opposed to using a reallly expensive HMI light???? I know that both will be at 5600K.... so is it just quality of light difference??

...vice versa, using a 5600K light with a CTO gel as opposed to using a tungsten light.....?????

I've been curious about this question for a long time... thanks
 
videomaniac said:
...anyone know the difference between using a tungsten light with a CTB gel as opposed to using a reallly expensive HMI light???? I know that both will be at 5600K.... so is it just quality of light difference??

...vice versa, using a 5600K light with a CTO gel as opposed to using a tungsten light.....?????

I've been curious about this question for a long time... thanks
Click to expand...

The diference is that HMIs put out much, much more light. I just finished shooting some spots with HMIs and the HVX and I'm glad I had the HMIs. I bounced 1200w HMIs off beadboard ( styrofoam sheets) and got more light than if I had a tungten 1K with frost pointed directly at the talent. HMIs are also very specular, very good for giving you a nice, vibrant backlight over a large area, essential, if you're shooting large furniture groups, like I was.
 
Hey thanks for the quick reply... that makes sense...

another question is you said that you were shooting a furniture set, so I'm assuming you are looking for an "indoor feel". If so, did you use a 3200K gel on those lights or will you be changing the color temp in post? which is better?

thanks :)
 
The light difference is in terms of light for the same amount of power. The difference is something like 5-6x the light for the same power. A 100w HMI is about the same as a 500w tungsten. So, if you need more than a couple lights and you have power issues, HMI's solve that problem.

Also, adding a full CTB on a tungsten fixture cuts a whole stop of light, cuts it in half. At that point you need a 1k tungsten to match a 100w HMI. Going the other way, adding CTO to a daylight fixture doesn't cut nearly as much light.

Finally, daylight is just plain better light, it has a fuller spectrum of light, fleshtones look better under daylight.
 
videomaniac said:
Hey thanks for the quick reply... that makes sense...

another question is you said that you were shooting a furniture set, so I'm assuming you are looking for an "indoor feel". If so, did you use a 3200K gel on those lights or will you be changing the color temp in post? which is better?

thanks :)
Click to expand...

I just used the lights straight with no color gels. I had some ambient incandescent, (I was shooting in a store) but if you white balance, you shouldn't have too much problem. I always do some post color correction.
 
Joshua Provost said:
The light difference is in terms of light for the same amount of power. The difference is something like 5-6x the light for the same power. A 100w HMI is about the same as a 500w tungsten. So, if you need more than a couple lights and you have power issues, HMI's solve that problem.

Also, adding a full CTB on a tungsten fixture cuts a whole stop of light, cuts it in half. At that point you need a 1k tungsten to match a 100w HMI. Going the other way, adding CTO to a daylight fixture doesn't cut nearly as much light.

Finally, daylight is just plain better light, it has a fuller spectrum of light, fleshtones look better under daylight.
Click to expand...

AWESOME response... I completely understand now... THANKS
 
HMIs are typically around 3x the light output for the same wattage tungsten lamp, but it could be more or less depending on the age of the bulb, manufacturer, ballast, etc. About 80% of the energy used in Tungstens comes out as heat - due in large part that most of their light output is in the IR spectrum.

Full CTB cuts 2 stops of light from Tungsten sources, while CTO cuts 2/3 stop of light. So even full CTO on HMI would output more from a similar wattage Tungsten with zero filtration.

So why would anyone pick Tungsten over HMI you might ask?
Well, Tungstens are relatively CHEAP. For the price of one new HMI (or even rental for the larger ones), you could buy several Tungstens. They are comparitively simple to use - plug them in and that's it. No head cables, no ballasts, no PAR lenses, pretty consistent color temperature, their color spectrum is continuous (and in some people's opinions it better matches video sensors), no power factor correction considerations, no worries about hot-starts turning the lamp into a cannon, no extended warm up time.

HMIs are more power efficient, emulate Daylight Color temperature, and far fewer units are needed to acheive the same effect with Tungsten units - so less pulling cable, and with the PAR units, you get a different level of control with the various lenses.
 
pheboglobi said:
Full CTB cuts 2 stops of light from Tungsten sources, while CTO cuts 2/3 stop of light. So even full CTO on HMI would output more from a similar wattage Tungsten with zero filtration.
Click to expand...

...very good info to know.. thanks
 
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