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Old January 17th, 2008, 10:48 AM   #1
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Down-lamping vs dimming a 1K Arrilite

When I bought my lights, I really didn't know how much light I would need. I bought a 650 fresnel, and a 1K open-faced Arrilite.

I use them to light drama films indoors, and I've discovered that I really did buy far too much light. Now, I can use ND gels, and I do have a couple of those popular $10 dimmers and those work great. But now I've started to think about down-lamping the Arrilite.

I figure I probably should have just bought a 300 watt fresnel instead, or even just another 650 watt fresnel.

Am I better off downlamping the Arrilite 1K to 600watts and starting the dimming slightly from there, or keeping it at 1K and just relying on dimming and ND gels.

I know that once you dim drastically you change the color temperature. But is that the worst that can happen? I'd hate to damage my lights because I want to dim a 1K all the way down simply for an edge or hair light.
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Old January 17th, 2008, 10:57 AM   #2
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You can use also scrims to reduce the light output. It's not unusual to use larger lamps on dramas and then scrim/ND down, it's a lot quicker than changing lights.

If you use CTB gels on your lights, you quickly discover that you need the bigger units, especially if you use diffusion or bounce.
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Old January 17th, 2008, 11:23 AM   #3
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Good point. I am actually using scrims instead of ND gels, though I plan to pick up some ND gels soon.

I do use diffusion gels also, so I agree that those cut down the light quite a bit as well. I guess I just worried that I would still have to dim-down quite a bit, and I was worried about damaging my lights somehow.

What's the worst that could happen, would it just break the lamp or could it damage the fixture?
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Old January 17th, 2008, 11:48 AM   #4
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Originally Posted by Craig Irving View Post
...I guess I just worried that I would still have to dim-down quite a bit, and I was worried about damaging my lights somehow.

What's the worst that could happen, would it just break the lamp or could it damage the fixture?
Dimming will not damage your bulbs or fixtures, on the contrary your bulbs will last longer.

The cons - you're using more power than you need, which can be a problem if you have limited power service in a location. This power is being dissipated as heat by the dimmer. You have to carry the dimmer, setup is more complicated. Biggest issue to me is that you're changing the color temperature of the light (towards the warmer) with the dimmer.

A warmer color temp can be a good thing, or a bad thing, depending. For me, I'd rather lamp down (still carry the 1K lamp with me, it's small and light), so that all my lights are the same color temperature. You can always throw in some rose or cto to warm things up when you want them warmer, but most people are going neutral and cc in post.

The exception is backgrounds. If you want the background colder or warmer than the subject that is best done with gels in the bg light while shooting.

PS. what Brian said about CTB for daylight balance sucking down the light intensity is a serious consideration. Using CTB typically means needing twice the light, so, do keep that 1K bulb if you lamp down.
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Old January 17th, 2008, 11:49 AM   #5
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Originally Posted by Craig Irving View Post
Good point. I am actually using scrims instead of ND gels, though I plan to pick up some ND gels soon.

I do use diffusion gels also, so I agree that those cut down the light quite a bit as well. I guess I just worried that I would still have to dim-down quite a bit, and I was worried about damaging my lights somehow.

What's the worst that could happen, would it just break the lamp or could it damage the fixture?
Hi Craig:

Dimming fixtures will not harm them but it will turn the light coming from your Arri 1k a nice orange color and you will get noise, physically from the instrument and sometimes in your audio chain.

Between barn doors, scrims and ND/Diffusion, you can take an Arri 1k down to almost nothing without resorting to a dimmer, I do it all of the time. Brian's point about having the extra horsepower when you need to CTB those lights is a really valid point. Shoot a daylight interior with an Arri 1k with full CTB through a Chimera as a key and you have about what a 300 watt fresnel does without CTB. It's easy to reduce light but impossible to increase it.

Best,

Dan
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Old January 17th, 2008, 02:48 PM   #6
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If you do want to keep using the dimmer. I have heard that as long as you don't go bellow about 50% the color temp shouldn't really change. I have no way of testing this though.

By downlamp do you mean just replacing the bulb? If so I think that would be a great idea if the ends match up, and you could keep the 1k bulb around for when you need it.
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Old January 18th, 2008, 11:50 AM   #7
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If you do want to keep using the dimmer. I have heard that as long as you don't go bellow about 50% the color temp shouldn't really change.
Hi Eric

Not true. I use a lot of dimmers with my tungsten lights and you can see a color shift with as little as 10% dimming. 50% dimming will radically change the color temp.

Dimming is fine when you want a warm orange BG but is really too much when keying people. If you go too orange, especially with 4:2:0 formats, you will not have enough latitude to ever color correct it back to a natural skin tone.

Just wanted to give you what I have experienced.

Dan
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Old January 19th, 2008, 04:58 PM   #8
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Thank you for the correction.
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Old January 19th, 2008, 08:53 PM   #9
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Thank you for the correction.
No prob Eric, just hate to see someone try that and then get backed into a corner. I have measured my tungsten instruments with a Minolta color meter and there is an almost immediate shift when dimmed and it accelerates exponentially as the lights are further dimmed.

Great for BGs and tabletop, not so healthy for skin tone unless you like all your talent to have the "Fake Bake" look. ;-)

Dan
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Old January 19th, 2008, 09:47 PM   #10
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If your lights are always too bright, it's a good idea to put in lower watt lamps (bulbs).

It is not a problem at all to use a smaller watt lamp. Using a lamp the right size saves on heat and watts pulled. The only precaution is to not touch the glass with bare fingers, leaving a bit of oil on the glass. Oil heats to a higher temperature than the glass will normally, a hot spot is created where the finger mark burns in and the glass becomes a bit milky. This greatly increases the likelihood of an explosive lamp failure. (If the glass on a lamp is touched, it should be clearned immediately with a soft cloth and maybe alcohol.)

You can carry the higher watt lamps in a small protective lamp pack in case you need them. Lowel makes some little plastic boxes with cutouts for lamps that are very good:
http://www.bhphotovideo.com/bnh/cont...arch&Q=*&bhs=t
The Lowel ones sometimes need a rubber band to keep them closed. I'm sure other companies make them, too. The Lowel lamp packs, for example, are much more protective than keeping spare lamps in their cardboard containers.

If you are using Fresnels, you can have a number of little ND filter cut that quickly go into the gel/filter holder. You can carry a combination of ND, diffusion, CTB and CTO. You can have a big range of little squares for each light and still be toting around much less than 1 dimmer.

A dimmer can be helpful on backgrounds and/or when you are using colored filters.
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Old January 24th, 2008, 02:42 PM   #11
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I have heard that as long as you don't go bellow about 50% the color temp shouldn't really change
A gaffer in a lighting course once told me to never go below 70% with tungsten lamps because of the color temperature. I was doing my job training at the time and he said that in the final exams, dimming below 70% would be counted as a mistake with at least minus 5 points (out of hundred)
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Old January 24th, 2008, 04:46 PM   #12
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That's pretty funny--can I assume that the wording of the question precluded the concept of dimming tungsten down to warm it up, such as matching incandescent bulbs in the scene or firelight?
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Old January 27th, 2008, 12:47 PM   #13
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That's pretty funny--can I assume that the wording of the question precluded the concept of dimming tungsten down to warm it up, such as matching incandescent bulbs in the scene or firelight?
Well, it was pretty basic and we knew the task would be exactly this: 3-point light one person in front of a green screen for a tv presentation (note: don't be creative, just do it according to the book - it didn't say that, but it was what they meant). Dimming too low would have warmed the color temperature too much, so they wouldn't accept it...
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Old January 27th, 2008, 01:15 PM   #14
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Right, it would have been scandalous to think that you would give someone a healthy looking skin tone by warming up their key source a little...!

I'm not trying to be too judgmental (well, maybe a little) but it kills me to think that people are penalized over something like that that is simply not an absolute of right or wrong--this is lighting for the camera, it HAS to incorporate a "creative" element in order to be successful (unless the goal is simply to provide enough illumination to make the engineers happy, which is probably the case more often than not in that end of the industry). Is there a technical reason not to warm up a source by dimming it? No. Does it hurt the potential green screen key? No. Might it actually improve the look of the subject? Yes. Especially if it was the backlight.

So in this instance doing it by the "book" is to end up with footage that is potentially less pleasing, all out of principle. But then again, live TV is often marred by this sort of thinking. The idea that making a subject look good is a "creative" decision instead of the absolute priority is just baffling to me.

Sorry about the rant, Heiko!
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Old January 27th, 2008, 03:48 PM   #15
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I know exactly what you mean, but the school was pretty caught up in the bureaucracy of public television. Interestingly whenever I talked to someone there in private they were always open to creative approaches and seemed to be very capable people.

However, the rule not to dim below 70% serves the purpose of staying in a very small range of color temperature. For some purposes (exact color reproduction) this is definitely welcome, you can't say there is anything wrong with that. And they just needed to set some rules - how else would they be able to give grades for what is mostly a creative process? Let everyone do their thing and in the end say "hmm I like the looks, I give it an A"?
Considering it was a very basic lighting education, I guess setting some stupid rules was necessary. I feel free to break them whenever I like (and that is very often ;) )
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