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Dimming for HMI575 lamps


khayamanzi

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Please excuse the intrusion here but I have a question which I am sure is very simple to answer for you people way above me in the 'technician' league!

 

At my school, we use a followspot that uses an HMI575 lamp as supplied by Terralec. This is it! Now, this years production of Ebeneezer really requires the spot to be dimmed. Is this possible and what would I need to get to do it?

 

Please accept my apologies if this question is far too simple and silly for many of you but I'm hoping you can help?

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Only with a mechanical dimmer. These are normally a set of barndoor like flaps on the front of the lantern. I doubt Terralec make them, but you might be able to adapt a set from another manufacturer. Used Lighting had a set a few weeks back...

 

Yep, still there. http://www.usedlighting.co.uk/used_lightin...e_catalogue.htm and have a look at the Pani dimmer under Follow Spot Accesories

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Normally, discharge followspots are dimmed in the same way as moving heads, with a shutter, controlled, for a followspot, by the operator. As such, they don't actually dim, just the amount of light that is outputted is reduced.

 

I would have suspected that all discharge followspots would have this, but as you don't appear to know of one, and it isn't specified on Terralec's website, I wonder if it isn't incorporated.

 

 

quote snipped

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The normal trick is to put a bit of black wrap in a colour frame holder and have the operator hold it half in to dim, but I don't know if that thing has a conventional colour frame to accommodate this.

 

If you just need the thing to be dimmer, then I would suggest some one or two stopdown gaffer taped over the front, or just focus for a very wide angle and use the iris to bring the beam size down to what you actually need (hard on the iris however).....

 

One thing that will not work is plugging it into a dimmer (Likely to damage the dimmer and lamp).

 

Regards, Dan.

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A huge thanks for all your help and patience with me!

 

Yes, I believe it does have a blackout shutter but using that alters the shape of the light picking out the actors and I wanted to make it dimmer rather than alter the shape - oh well, back to plan A and that is simply using coloured gels to soften the light for each scene I require this. Many thanks once again.

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As suggested black wrap is a good way to dim but only really usefull if you want to dim from full to blackout. If you want to dim from full to some where in between for any extended period then netural density filter as Dan suggested (as shown here) in one of your colour slots is the way to go.
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A huge thanks for all your help and patience with me!

 

Yes, I believe it does have a blackout shutter but using that alters the shape of the light picking out the actors and I wanted to make it dimmer rather than alter the shape - oh well, back to plan A and that is simply using coloured gels to soften the light for each scene I require this. Many thanks once again.

 

I'm assuming that AndrewC's pointer is no use for budget reasons (if not then give Usedlighting a ring, they are very helpful)

 

you could always just make a psudo dimmer thing (or a horrible bodge, depending on your point of view)

 

its just a matter of putting thin strips of something black and heat resistant across the colour frame (in your changer)

Blackwrap does work, but it also tends to stick to anything else in the changer....

 

If you look at the way a louver dimmer works its exactly the same principle, just try and make the strips thin, looks better.

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I think that he is refering to the fact that when you do use a card in the colour changer to act as a dimmer it can be very noticeable. Normally only at very low intensitys, but noticeable non the less.

 

And by noticeable I mean that the spot gets darker from the side where the card is entering, not evenly. at the lowest levels the spot can end up going almost cresent shaped.

 

edit:

 

just thought about it some more, it will be a blackout shutter, same as in a pani 1200, (not the 1202) which will have the same problems as a card. but worse.

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