lighting myths and sales pitches

Sun, 8 Oct 2006, 10:35 pm

David Ashton12 posts in thread

I sell and repair gear,[declaration of interest]and I see on a weekly basis people being sold stuff they don't need or can't use and I would like to start off a thread of things to look out for.One big sales pitch which can cost thousands of dollars is the DMX sale.A DMX dimmer is in fact an analogue dimmer with a DMX decoder built in,DMX is not a type of dimmer ,it is a system of transferring data.So should you buy new dimmers?.Dimmers are like cars, there are good models and bad ones, unfortunately it usually takes a few years to find out.If you have good reliable analogue dimmers then buy a demux for $400 and keep the dimmers as new DMX units are going to cost $2000 per 12 way.The old Strand JTM and Minipack dimmers were particularly reliable.On the subject of desks, DMX desks are now so cheap they can be considered a consumable with a 24 way memory desk at $400 and a 48 way atb $660.Incidently no one has mentioned that Strand UK has gone broke and will not be selling or servicing gear any more.Another sales con is the RGB floods with a dmx controller,not only are they overpriced but highly inefficient as 80% of the light is lost in the filters and as you dim down the blue, the colour temperature of the lamp reduces so there is no blue content to dim.Finally a word on the quaint practice of pre-heating lamps, I recently got into heated discussion on this practice which lead me to do some experiments which proved that preheating lamps had virtually no effect after 4-5 mins and absolutely no effect after 25 minutes, so if you preheat your rig you can save time, power and lamplife by discontinuing this practice.Ilook forward to other feedback in this area.

I must agree with Daves

Mon, 9 Oct 2006, 12:00 pm

JoeMc

I must agree with Daves post that in a lot respects the preheating is a myth.
Having cut my teeth on lighting back in the 50’s working with mainly vacuum bubbles, which a lot of Comeatre rigs will still be using, along with the gas filled ones in lot of older style lamps & hay burners. Preheating with the vacuum bubbles is still of value especially in cold conditions. Invariably when the filament is cold the power surge of an initial full power snap on or flash, will pop the bubble or damage the filament further. However this is dependant upon it’s previous usage & the inevitable thinning causing weak spots in the filament wire.
This site explains it better, while no means being an actual scientific data based test;-
http://freespace.virgin.net/tom.baldwin/bulbguide.html

I still find a good practice is to pretest the rig at about 10 -20% & do a quick walker, to check if that all the lamps are working before the show, when it is easier to visually check.
A lot of desk manufacturers use a built in preheat mode & this usually only helps with performing the preshow test.
although when initially switching on Par cans from cold, you may experience a slight delay before they reach the optimum operating temperature. Similarly with QI lamps which have been run on very low for extended periods, the quartz envelope tends to blacken up. Which reduces light output further, but running on full for a short period will clean it up. In fact a lot of Architectural lighting systems have a periodical built in automatic cleaning mode, by putting them on full for a short time.

Thanks Dave for pointing out the inside story & some of the pit falls on equipment available.
It great to get "Tech Talk’ postings of interest again, it’s almost as exciting as using Salt Water Dimmers!

Thread (12 posts)

Threaded Flat

lighting myths and sales pitches— David Ashton8 Oct 2006

Issues— Na9 Oct 2006
I must agree with Daves— JoeMc9 Oct 2006
- warming globes— David Ashton9 Oct 2006
This is the press release— JoeMc9 Oct 2006
- strand takeover— David Ashton9 Oct 2006
What the f.......!!— Walter Plinge9 Oct 2006
Yes it is rather sad that— stephendean9 Oct 2006
Your right Dave if the— JoeMc10 Oct 2006
- lamp pre-heating— David Ashton10 Oct 2006
  - Perhaps one for the— Na10 Oct 2006
Learn how to write.— Walter Plinge10 Oct 2006

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