Osram Dulux EL Vario 23W/41-827 Self-Dimming Compact Fluorescent Lamp

Initially, this may appear as nothing more than your garden variety 23W Osram Dulux EL.  Until you look a bit closer that is.  Visually there's only one clue to this lamp's rather unique trick, and that is that the base is a little larger than you would usually expect these days for a lamp of this wattage. 

The reason for this extra size is that the lamp here contains circuitry which allows this lamp to dim itself.  Giving you access to two brightness levels (100% and 30%).  One of the biggest drawbacks people have seen with compact fluorescent lamps, is that they cannot be dimmed with conventional hardware.  Neither variac nor phase control dimmers will work with them - and more often than not, trying to will lead to early or instant destruction of the lamp, the dimmer, or both.  This is irrespective of the fact that the lamps *will* generally dim, to at least some extent.  It's not good for them.

Osram obviously know this, and have launched this, the "Vario" version of their highly successful Dulux EL 23W lamp.  It doesn't take a hugely observant person to spot that this lamp has no external controls or anything, not that this would be a particularly practical solution anyway.  So how on earth do you go about selecting either of its two brightness levels?  It's actually very simple.  When you first turn the lamp on, it will start up at full brightness.  If you switch the power off briefly, then back on again, the lamp will relight at the lower level.  Powering it down and up again will toggle it back to full power again.

The first quirk I spotted (or rather the person who donated the lamp for this collection told me) isn't a major thing, but it is worth noting I think, which is that the lamp will not reliably operate in low mode until it has been allowed to warm up for at least a couple of tens of seconds on high.  Sometimes it will let you switch straight to low, other times it'll just blink, then reset to high again if it's cold.  Once it's warmed up, the changeover seems to be entirely reliable.

On high it's a bright lamp, as you'd expect for an Osram product of this rating really!  It does show how things have come on in the last few years though.  I have a 23W Philips lamp from the late 90s, and using this does show that things have moved on quite a bit in terms of efficacy.  Performance when dimmed though I find a little disappointing.  First reason; flicker.  The lamp does flicker when dimmed.  Not a 50/100Hz flicker, but an erratic one; it isn't terribly noticeable, but it is there.  Some people are more likely to pick up on it than others, I would have done even if I wasn't analysing it.  Secondly: Colour temperature.  When the lamp is dimmed, the colour temperature does shift downward a little - nowhere near as much as an incandescent lamp dimmed to the same degree would, but it's a noticeable shift.  The images showing the lamp lighting my workstation below were taken without any alteration in the colour balance settings between the shots, you can see that the latter (low) is slightly warmer than the former (high).  Also the efficacy of the lamp suffers somewhat when it is dimmed, but that's more down to the physics of how a discharge lamp works than a drawback of this particular design.  Of course, even when dimmed, it's still managing over 35Lm/W, which is considerably better than a standard 40W incandescent lamp (which is what I'd say the low level output was roughly equivalent to), and the lifetime will be many, many times longer than its incandescent counterpart obviously.

A major application I can see for this lamp is in buildings such as hotels, where round the clock lighting is required - but not necessarily at the same level all the time.  At a local hotel here, the corridors on the ground floor see little traffic at night, and just a couple of lights are left on to give low level illumination.  That's where this would come in.  Rather than having to have a bunch of separately switched lights, just put these in, then select the low level for the evening, and switch back again in the morning.  Would still be saving power, and would mean that the whole corridor would still be lit to a useable level, rather than having the dark bits between the lights which stay on at the moment. 

It's not a perfect design, Osram have a couple of things to address with it - the tendency for the lamp to flicker when set to low mainly - and the extra bulk could be a problem in a couple of cases, mainly because that adds to the length of the lamp by 15mm or so.  They have however proved that it can be done, and no doubt a plethora of other manufacturers will over time come up with designs along the same sort of lines.  Self dimming incandescent lamps have been around for a while now, and despite the technical complications involved in making a compact fluorescent lamp which can do the same, this proves that it can indeed be done.

Osram Dulux EL Vario 23W/41-827 Self-Dimming Compact Fluorescent Lamp - General lamp overview

Osram Dulux EL Vario 23W/41-827 Self-Dimming Compact Fluorescent Lamp - Detail of lamp cap

Osram Dulux EL Vario 23W/41-827 Self-Dimming Compact Fluorescent Lamp - Lighting my workstation from approximately two metres set to high brightness

Osram Dulux EL Vario 23W/41-827 Self-Dimming Compact Fluorescent Lamp - Lighting my workstation from approximately two metres set to low brightness

Osram Dulux EL Vario 23W/41-827 Self-Dimming Compact Fluorescent Lamp - Overview of lamp while lit

Osram Dulux EL Vario 23W/41-827 Self-Dimming Compact Fluorescent Lamp - Overview of lamp packaging

Osram Dulux EL Vario 23W/41-827 Self-Dimming Compact Fluorescent Lamp - Shown next to a ruler for scale

Osram Dulux EL Vario 23W/41-827 Self-Dimming Compact Fluorescent Lamp - Detail of text printed on lamp base (very faint on this particular lamp).

This lamp added to the Virtual Display Shelf on the 8th December 2005 at 22:21.

References:

Osram Dulux EL Vario Datasheet from Manufacturers website. (Dead link removed - April 2023).

Acknowledgements:

Many thanks to the website reader who donated this lamp to me!  You know who you are!

This page last updated on the 15th of June 2023: Made changes to page formatting to improve readability on mobile devices.  Have also made some background code changes to improve search engine behaviour.