My comparison of the brightness of different kinds of light-bulb.

Two days ago I tweeted a contribution to the upcoming 10:10 forum on LED lighting:

@1010 We have two LED bulbs billed as 60W replacements by Homebase which are much brighter than 100W

When this provoked some interest I added that I had kept meaning to test this impression by using the light meter of my camera.  10:10 replied that they would be interested in the results. So, waiting only for darkness to descend, I went ahead with my simple experiment. Which confirmed my assertion, thus:

Method:

Setup

IMG_20140211_190935Lumix G2 camera set on Aperture Priority mode.  Sensitivity at ASA 1600  Aperture fixed at f3.6

Night time. No other light sources present.

The only change made between each reading was the  bulb itself.

The two mini fluorescent examples were allowed to warm up to full intensity before taking their readings.

Results:

  • 60 Watt Incandescent:      1/60th second exposure required*
  • 100 Watt Incandescent:    1/100th second exposure required*
  • 15 Watt mini-fluorescent:   1/100th second exposure required*
  • 12 Watt LED:   1/160th second exposure required*
  • 30 Watt mini-fluorescent:   1/200th second exposure required*

*The amount of light produced by the bulb is presumably in inverse proportion to the length of the exposure required – i.e. the shorter the exposure the brighter the bulb.

Conclusion:

These results suggest that while the 30W mini-fluorescent is the brightest bulb tested, the 12 Watt LED bulb bought from Homebase produces nearly three times as much light as the 60 Watt incandescent bulb for which it was billed as a replacement, and is more than half as bright again as the 100 Watt example, just as I claimed in my tweet.

Discussion:

One factor inhibiting people from changing over to LED lighting in their homes (apart from the cost – which is falling dramatically) is the belief that you can’t really get an adequate replacement for a standard 100Watt light bulb. Homebase, at least, appears to be contributing to this misconception by underselling the particular LED bulb which I used in this comparison.

I had no means of testing the accuracy of the wattage marked on the different bulbs, but if these are roughly correct then this experiment also supports the commonly repeated claim that LED bulbs use approximately 1/10th the electricity for the same light output.

I can feel further blogs coming on re:

  • The emerging practicality of large-scale changeover to much more efficient means of domestic lighting
  • The enduring validity of amateur experimentation, even in cutting-edge areas.

Bulk Archive in Gmail

I have just found a solution to a Gmail problem that I could not find by searching on-line

A close relation had 11,000 emails in her inbox and wanted to archive them to get them out of the way. Doing 50 at a time (which is apparently all that is allowed) was a waste of too much of her, or my, life.
Here’s what I found you do:
  • Come out of Inbox by choosing ‘All Mail’.
  • Tick the ‘Select All’ button, top left.
  • Look for the message which says ‘All 50 messages on this page are selected. Select all 52,479 messages in All Mail‘ (or however many you’ve got)
  • Click the underlined link in that message
  • Press the Archive tab (Yes – you seem to be archiving things that are already archived!)
  • Say Yes, (= I really do want to archive 52,479 messages)
  • Wait for a minute or so
  • Bingo!  Clean inbox.
This may be blindingly obvious to everybody else, but it foxed us for quite a long time. Perhaps it will help someone else.

Who is the most dangerous of all… ?

Letters to the Guardian are not available online so I have taken the liberty of copying and posting one which is in today’s paper under the heading Fantasies shaping children’s futures :
“If what you want is to understand Michael Gove as a public figure in charge of the nation’s educational needs, there is little point in debating what he might call his “ideas” (Letters, 4 February). One needs rather to focus on three things. First, and notwithstanding the acquired, but now melting, patina of Oxford cleverness, his manifest stupidity, apparently incorrigible. Only an idiot could seriously maintain that a day will come, causally engineered by none other than Michael Gove himself, when it will be impossible to distinguish state schools from fee-paying schools – a deft account of the sheer idiocy of this view is provided by Peter Wilby (Comment, 4 February).“Second, his fantasy life, that of a man lost in translation between past and present, and more precisely the fantasy, bordering on obsession, of the arriviste, wannabe toff drooling over the lexicon of long ago while dreaming of the glory days of “prep” and “lines”. Third, the political ambition. Despite all the guff about linking educational “standards” and “social mobility”, everything that Gove does as secretary of state for education serves a very precise purpose. Gove wants to be the next leader of the Tory party and one day perhaps prime minister.

“How do you use the education brief to best serve that end? By playing to the Tory right and making an educational offer to those sections of the electorate which, in the context of recession, no longer feel able to afford private education for their children. It is only a matter of time before the sharp-elbow classes swamp the academies and the free schools. Reintroducing the “common entrance” exam at 13 (another of the terms in the vocabulary of Gove’s regressive fantasy life; the common entrance, I ask you!) will seal the deal on that front.

“The rest is dross. Gove is not only the silliest member of the government; given that his compulsions and ambitions are currently shaping the future of millions of children, he is also the most dangerous. The priority has surely to be not debating him, but getting rid of him.

Professor Christopher Prendergast
King’s College, Cambridge
And this is the letter I have just submitted in response:
Editor,
Professor Prendergast finishes his otherwise superb letter (6 February) by suggesting that Michael Gove is the most dangerous member of the government. The competition is hot and the bar is high but the Secretary of State for the Environment, Owen Patterson, is surely far more dangerous. Yet even so the ultimate prize must go to the man who appointed such a known global warming denier to such a crucial position at such a crucial time.
J A R Willis