When to change lamps

[whitehousejamie]

In my stock of Macs, my 300's have GE lamps, and the 250s are using Philips lamps. Looking to replace them all soon, and wondering if anyone could give any reason to go for the Philips over the cheaper (and in my experience very reliable) GE version.

 

Secondly, after how many hours do hire co's usually change lamps? I am assuming this is after approx 800 - 900 hours, as the lamps do seem to loose light output around that time. Does this figure vary between the different lamp types?

 

Thanks in advance.

 

Regards,

 

Jamie

[SoLiEn]

imo, I would go for the phillips lamps, as they do tend to last a bit longer, I know a hire company who's entire stock of mac's run off phillips and they change them between 1400 and 2000 hours, depending on the light ouput. more often than not its at 2000 hours.

 

just my two penneth worth.

[niclights]

I will always change lamps minimum once a year, but it's worth taking note of manufacturers specified life to avoid explosion & resulting damage to optics/reflectors.

[johnhuson]

We looked at using different brands to what is the common type for each lamp is a while back. Spec's are exactly the same in most cases and our final decision boiled down to cost, we could purchase the 'usual' brand of lamp quite a bit cheaper than the alternative and when your looking to replace lots at a time it makes a difference.

 

We use the following in our fixtures:-

 

Phillips - MAC 250 Entour, MAC 250 Wash & MAC 600

 

Osram - MAC 700 Profile & MAC 550.

 

These are the brands supplied with the fixtures as new and are the 'usual' types from our experience so we've stuck with it.

 

In terms of changing we usually change when the majority of a type of fixture is around rated hours, the light output is generally getting quite poor by that time anyway. We always change all fixtures of the same type at the same time to avoid ending up with half a rig with new lamps and half with old as the difference between old & new lamps is usually very noticeable. Guess thats the advantage of halving tens of units rather than hundreds of units of each type!

 

We also always keep an eye on lamp hours and try and send out the fixtures with the lowest hours first to try and keep all the stock as consistent as possible.

 

Hope that helps, that's how we work can't say for others.

 

EDIT One thing I would say is always change lamps when they're at or close to the manufacturers stated lamp life. Exploding discharge lamps can be harmless but can also do a lot of damage to the internals of your fixtures. Also make sure you check the number of lamp strikes as well as hours, a heavily struck lamp will last significantly less time than one that burns for several hours at a time. I was once told that a single lamp strike knocks off around 4 hours from manufacturers recommended hours, not sure how correct that is but it's always worth leaving your lamps struck while you nip off for a cup of tea rather than dousing them each time.

[Andrew C]

Also make sure you check the number of lamp strikes as well as hours, a heavily struck lamp will last significantly less time than one that burns for several hours at a time. I was once told that a single lamp strike knocks off around 4 hours from manufacturers recommended hours,

Hmm, interesting. Any idea if a hot re-strike is better/same/worse for shortening life? My gut says "C".

[johnhuson]

As I said, not sure how true the actual time figure is but the number of lamp strikes does effect hours. I would imagine that hot striking would be more detrimental than cold but that is a pure guess on my part!

[Jivemaster]

Maybe relevant, The life of a discharge lamp includes a factor for decreasing light output. With a strobe tube the "life" is when the light falls to 50% of initial levels. SO various hours elapsed will mean various brightnesses.