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AnthonyMcPherson

Practical Tungsten Bulbs Question

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Hi, I'm looking to shoot a night interior scene and had a few questions about practical bulbs.

 

1. Is there a specific brand of bulbs that will work best? Or you can recommend?

 

2. Whats an ideal wattage for the bulb?

 

2. Do frosted bulbs work better?

 

4. Do I have to worry about tungsten bulbs flickering?

 

5. Is a dimmer necessary?

 

 

Thanks!

 

 

 

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1. Not really. In my experience the cheap halogen ones work about as good as the more expensive ones with the exception of bulb life and maybe robustness in terms of resistance to shock.

2. That depends on a wide variety of circumstances. How do you want to use them? As a practical in shot, hanging naked from the ceiling? Inside a lampshade, off screen? In a paper lantern, giving base illumination to a hallway? On what ISO are you shooting and what is the light level you need to achieve that? Generally speaking, as they are fairly inexpensive, I would get a small range of them, from 25w to 200w and then you should be suited for most situations. The lower wattages (25w, 40w, 60w) are the ones I reach for 90% of the time, you should have multiple of those, in frosted and clear. Generally speaking if you put a bulb in a paper lantern (so if you want to diffuse it further), it doesn't matter if you start out with a frosted bulb. Recently for a online commercial video, I used a clear one for the practical in the background first, but it ended up glowing too strongly because of the diffusion we had in camera, so we used a frosted one, which illuminated a lot more evenly and looked more pleasing and not as distracting (see attached photo). At other times I had cases where I swapped from a clear bulb in a practical to a frosted because the shadow line of the lamp shade was too pronounced, in which case I often add another sliver of 251 into the top of the shade to further help cut down on harsh shadow lines. If you are doing the classic single hanging bulb in a closet kind of thing, then you definitely want the hard look of a clear bulb. I would have a set of both close by and just experiment with what looks good.

 

4. I have never had any problems with halogen bulbs flickering, no matter whether they are dimmed or not.

 

5. Absolutely. You dont necessarily need to use the hand dimmers typically used for film lights, the cheap ones from Amazon will be fine for the smaller wattages. Be careful though, as these (and the better dimmers as well) start humming or buzzing slightly, especially in the middle of the dimming range. Try to keep dimmers away from set as much as possible, so in other rooms or whatever is far away enough for sound. Also, I often use bigger bulbs dimmed way down, so they read a lot warmer then 3200, which can be a very desirable look.

 

A final word of caution, be careful what bulbs you use with what socket. Most modern lamps have a maximum watt number labeled on them, which tends to be around 60w or 75w. Dont screw a 250w photoflood into the plastic socket of an IKEA practical, you might melt it and cause a fire.

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Thanks a lot Alex! that was an informative response.

 

I was gonna shoot at a lower ISO with the BMPCC 4K so I was thinking of using the practical then lighting my subject with a china ball.

 

Thanks again!

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Any household tungsten lamp is fine.

 

Wattage depends on your needs. I generally bring a range from 25 watt to 100 watt, with some higher jacketed lamps (250 watt) just in case.

 

Frosted would be better for most applications I would think.

 

Tungsten lamps don't flicker.

 

Dimmers are a necessity unless you want to waste time wrapping lamps with ND gel. The electronic dimmers can make the filaments vibrate at higher frequencies which are often audible to the ear. This is why you're better off trying to find an ideal wattage that doesn't need dimming, not to mention the lower color temp that (as mentioned) occurs when dimming.

Edited by Christopher Santucci

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.... Tungsten lamps don't flicker....

 

Tungsten practical bulbs will flicker at high camera speeds. Their filaments are so small that a high-speed camera will actually see the rise and fall of the current running through the filament. The solution is to operate them on DC current. Any tungsten lamp can operate DC as well as AC. In the old days we would string ten 12V batteries in series to get 120V DC, but now you have the option of using an AC to DC power converter.

CPS_Cultivate_Studio_HS_Prod.jpg

A DP I know was looking for some way to power a chandelier flicker-free for a high-speed commercial shoot (pictured above), I built him a 120V AC to 120V DC power converter so that he could power the chandelier and other practicals flicker free at high speeds (2000fps.)

CPS_30A_Power_Converter_SM.jpg

 

The one I built for him could handle up to a 1000W tungsten load, but I have since scaled up the design to handle a Jr. with CXZ lamp. The larger converter (pictured above) will accept input AC voltages from 90-140V, and 190 – 250V and put out a constant 120V DC. It can operate at both 50 and 60 Hz. It also has a series LED display to indicate the total load put on it between multiple tungsten Fresnels and incandescent practicals.

 

And, as you can see in the picture above, it is a lot smaller and lighter and more easily concealed on a set than ten 12V deep cycle marine batteries, wired in series, which has been the traditional approach to powering tungsten lights with DC on stages.

 

Guy Holt, Gaffer, ScreenLight & Grip, Lighting Rental & Sales in Boston

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...A DP I know was looking for some way to power a chandelier flicker-free for a high-speed commercial shoot (pictured above), I built him a 120V AC to 120V DC power converter so that he could power the chandelier and other practicals flicker free at high speeds (2000fps.)

The one I built for him could handle up to a 1000W tungsten load, but I have since scaled up the design to handle a Jr. with CXZ lamp. The larger converter (pictured above) will accept input AC voltages from 90-140V, and 190 – 250V and put out a constant 120V DC. It can operate at both 50 and 60 Hz. It also has a series LED display to indicate the total load put on it between multiple tungsten Fresnels and incandescent practicals...

 

Hey Guy, love your stuff! read a bunch on your website.

 

I'm going to infer that this was single phase US household power (please correct me if i'm wrong), my question is after you rectified the AC to DC what are you using to smooth the ripple voltage and how much power is lost on a 1000w circuit?

 

Is it half rectification or full?

 

Just trying to decide if something like this is doable on house power or if I should look into a battery solution.

 

Chris

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Hey Guy, love your stuff! read a bunch on your website.

I'm going to infer that this was single phase US household power (please correct me if i'm wrong), my question is after you rectified the AC to DC what are you using to smooth the ripple voltage and how much power is lost on a 1000w circuit?

Is it half rectification or full?

Just trying to decide if something like this is doable on house power or if I should look into a battery solution.

Chris

Full rectification and smoothing capacitors to take the rise and fall out of the pulsed DC that comes out of the rectifier. Its doable on hourse power since the converter is on a single circuit line-to-neutral it doesn’t matter whether the power is single or 3-phase, .

 

Guy Holt, ScreenLight & Grip, Lighting Rental and Sales in Boston

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