Lumens

How can you have a flashlight rated at 3 Watts?

http://www.theledlight.com/lumens.html

Lyn, the flashlights I am talking about are everywhere especially on EBAY, saying 3w Led flashlight or they change it up and say 1800 lumens. So I get real confused on what is actually meant by LIGHT, lumens and watt. The link you sent is a fantastic one and is a great start and i am reading it now.

Thanks

LPCS

If you open this link, you will find conversions for light that you never dreamed were possible: Conversion Factors

There is a notational error in the page http://www.theledlight.com/lumens.html, which is otherwise both interesting and useful.

The Candela is defined correctly here:

http://en.wikipedia.org/wiki/Candela

It is "...the luminous intensity, in a given direction, of a source that emits monochromatic radiation of frequency 540 times-Ten-to-the-twelfth-power Hertz and that has a radiant intensity in that direction of one-divided-by-six-hundred-eighty-three watts per steradian.

It would be simpler if there were html tags furnished on this site for superscripts and subscripts, but there are not. Most of the people who use CR4 understand "scientific notation" and would catch the error, but it never hurts to make things clear for everyone.

• "It would be simpler if there were html tags furnished on this site for superscripts and subscripts, but there are not."

You mean like this W²m^-2 or y = x₁ + x₂ + x₃ ...

You can also insert proper hyperlinks to topics like this one on the SI unit Lumen.

Not to mention inserting images that can be of more complex formula like this one.

All these functions with the exception of generating the complex formula which is an image of a formula created with Word, are available in the toolbar at the top of the CR4 editor window.

You can also insert a whole host of images like ∏≠≈ by clicking on the Ω symbol in the toolbar.

The toolbar you are talking about appears at the top of the window in Firefox and Camino but not in Safari or Opera. I use Safari most of the time, and the limited selection of tags isn't a problem, because my postings seldom include mathematical operators or subscripts or superscripts.

Those functions should be available using tags, but only four are listed, viz. hyperlink, bold, italic, and one to place an image in the post. They are not standard HTML. HTML is not hard to use, but only the correct code obtains the desired result, and I don't know what that code is for those other functions.

G'day bubbapebi,

If your browser is working correctly then the CR4 editor toolbar should appear at the top of the editor window as shown by the red arrow in the image below.

However, people have had problems in the past due to very old editors being loaded from their cache and as a result it doesn't have the all the tools. However, it should be there as it's part of the CR4 web page and has nothing to do with the browser you are using.

· "Those functions should be available using tags, but only four are listed, viz. hyperlink, bold, italic, and one to place an image in the post. They are not standard HTML."

Yes I know CR4 doesn't accept HTML controls but it also allows you to insert hyperlinks, use superscript, subscript, underline, cross out, bullet points, number points, insert a whole host of mathematical symbols and even add the occasional smiley, as shown in the enlarged toolbar image below.

I agree it's not a brilliant editor but it does pretty much all you need for a CR4 post and for more complex things you can always do what I and others do and that's turn it into an image and insert that as I did in my previous post with the equation.

If you are not seeing the entire CR4 editor toolbar then there is something going wrong with the browser because the entire toolbar is part of the CR4 web page and should be displayed as such.

Several attempts to insert the image below in Safari using the tags provided on the page failed, although "BOLD" and "italic" worked OK. This reply was sent using the web browser Camino, which displays the toolbar.

This application accepts .jpg but not .bmp or .tiff. I used .png, which yields a higher-quality image than .jpg. It probably also accepts .gif, although I didn't try that one. The re-sizing option also worked.

It would be nice to have something that works with other browsers available so that switching browsers isn't necessary if a posting includes a graphic of some kind.

The image you inserted looks like you are using a very old version of the CR4 editor from about 4 or more years back. At that time it would accept a limited number of HTML tags but it couldn't do things like superscript, subscript etcetera.

This has happened before and usually turns out to be caused by your browser using an old version of the editor that it has cached rather than downloading a new version every time. I'm not familiar with the browsers you are using but the first thing I would try was to force it to download a newer version of the editor. One way to do this is to erase the browsers cache but again I don't know how to do it with your browsers. You may also have a problem with your browser blocking cookies and other downloadable code that can be executed. Try turning off those security features for the CR4 web site and then opening the editor again.

One other thing that might be worth trying is to try Microsoft's Internet Explorer which is what I use. If the toolbar doesn't appear with that then the problem is more than likely to do with the security features you have enabled.

If you still can't get CR4 editor toolbar to appear then I suggest you try contacting the CR4 admin crew and sending them the image you posted.

One work around is to do what I do and write up the text of your post using a text editor like Word that has the same sort of features the CR4 editor toolbar has. Cutting the entire post and pasting to the CR4 editor window will then transfer any of the extended text features like superscript, subscript, underline, bold, italic, strike through, symbols and hyperlinks that the CR4 editor can cope with. If it can't cope with a feature then it will just leave it as an ordinary character.

I hope that helps and allows you to access the proper CR4 editor.

Thanks for the tip, masu. My online computer is a Power Macintosh G4. for which there is only a very old version of Internet Explorer, used to view web pages that will only open in IE (whose number is dwindling, by the way).

I'll try clearing the Safari and Opera caches, but if that fails to correct the problem will use Camino (which has the toolbar) for postings that require a graphic of some kind. Firefox is loaded with NoScript, so that one comes in handy for viewing any web page so loaded with scripts that it stalls my trusty old Mac (500MHz, 1GB RAM) but that very useful add-on also blocks Adobe Flash videos, so it isn't my usual default browser.

The link that Lyn provides in response #1 is very good. But keep in mind your flashlight does not radiate over a full spherical region of 4 pi steradians, so you would somehow need to correct for that. If you have a lumens photometer it does not matter at what distance you measure the light source; so long as you know the distance, you can calculate the number of lumens. One of the problems with measuring a flashlight like this though is that the output is probably not uniform, so depending on where in the beam you measure it you can get wildly different values.

I do have a meter and it does change with ever slightly moving a flashlight beam. Big difference at one, two and three feet.

There is a good way to figure lumen of CREE LED: use Integrating sphere and Spetrometer to measure, you can review the full solution at: http://www.lisungroup.com/product-id-198.html

According to the Specification (PDF 0.55 MB), there is a test report, you can get not only the lumen parameters but also have other color and electricity parameters for the CREE LED.

LPCS,

What ever happened to your "spent" light harvesting project?

This is still in work, GE is still making a decision on the submissions.

One of the greatest things about the ability to ask a question is the results you get from all of the post's here at The Electrical Engineering Section. If you have a question it will get resolved and in a way that you feel you have every possible answer to your question,

I never knew that there were this many ways to look at a Lumen and I know more know than I have ever expected to have kown.

Thanks to all of the inputs and my appreciation for the great answer to my Question of how to fugure a LUMEN> Amazingly great bunch of well tuned professionals. Thank you so much for your help.

LPCS

Lumens of a lamp is 'The Total Luminous Flux emitted in ALL Directions'. This used to be measured in a very expensive measuring device. A ball of sensors was used. The lamp for testing was mounted in the centre and sensors measured 360 degree in ALL Directions, giving the Total Luminous Flux produced. This method gave total brightness in ALL Directions But it was noted that each square metre of sensors, around this measuring ball, received the same amount of brightness from the lamp, so a much simpler and less expensive machine was developed. This just measured only 1 square metre of area, or 1 steradian, of the sphere. Because All the 14 steradians each receive the SAME amount of light, you only need to measure 1 steradian and multiply this figure by 14, to get total brightness in ALL Directions. So the new improved machine only measures 1/14 of the area and assumes the Total Brightness is 14 times this measured area. This is fine for measuring the total brightness of a lamp without any reflectors or concentrators, but an LED or Torch, has a reflector or Lens, which FOCUSES ALL of its brightness into one bright spot of light. This is then assumed, by the machine, to be only 1/14 of the brightness and is then given as 14 times greater than the real Lumens.

So if you want to measure the REAL Total Luminous flux, you MUST measure the total brightness all around the lamp with no reflectors and no lenses. Or measure the brightness over 1 steradean WITHOUT lenses or reflectors and multiply by 14, or measure 1 steradean with the reflector or lens and divide it by 14 to get Total Luminous flux.

So in Total Luminous flux, a 55 Lumens LED is really 4 Lumens, while a 55 Lumens filament lamp is 55 lumens. The filament lamp is far more energy saving than an LED to get the SAME brightness all around a room.