LED advice

[Flyfisher]

Ditto everything regarding home photo printing. The results can be very good but inkjets seem to work best when used regularly. I was photo printing so rarely that I was having head-blockage problems and seemed to use half my ink just cleaning the heads prior to achieving a worthwhile print (OK, slight exaggeration, but not much). There's so little in the pricing that the ease of online printing far outweighs the immediacy-but-hassle of home printing IMHO. I've also had excellent results with online printing up to 20x16 inches, something not possible at home without buying a very serious printer indeed. And, yes, a cheap B&W laser printer is a no-hassle option for printing everything else.

Picasa doesn't do anything to your jpegs, it just analyses them and builds its own database. It doesn't even change the file properties. You could give it a quick try by just restricting it to searching with a couple of folders-worth of photos.

I'm very wary of 'cloud computing', even for backups. Even an 8Mbps broadband connection would take ages to restore a 500MB hard drive if it failed, and that's without all the security and reliability implications. It's my stuff and I want to be in control of it, not at the mercy of some server-farm built on a geological fault-line somewhere halfway around the world.

 

[AMc]

The Playstation Network breach has pointed out a fairly serious issue with Cloud computing to me. It's only a gaming network but it's been down for weeks and will stay down until the end of the month because of a problem in their security.
I still haven't been able to discover if I had a valid credit card attached to my account because I can't login to check - all it all a lesson learned.

I'm on a rural ADSL connection so I'm lucky to get a 0.5Mbps upload speed - restoring down at 3-4Mbps would be OK but 20GB wouldn't be much fun Hence only uploading the very best stuff usually with an intention to print.

Found the receipt for this computer looking for something else £300 in September 2004 - I think I may be due a replacement

 

[Penners]

I was having head-blockage problems

I sympathise. I've suffered from that for years.

 

[Flyfisher]

:lol: :lol: :lol:
Actually, now you mention it, I've had a real head blockage for most of the week.

It's been ages since I've had a real stinker of a cold - as Mrs FF calls it, even though us chaps would immediately recognise it as some sort of exotic, near-fatal lurgy, hitherto unknown to medical science.

I'm looking forward to being able to breathe through my nose again soon.

 

[Pford75]

Considering these downlights.....

•Description: High output LED downlight.
•Wattage: 17W / LED replacement for a 50W low voltage halogen downlight.
•Finish: Grey aluminium.
•Life expectancy: 30,000 hours.
•Colour appearance: 830 Warm white
•Colour temperature (CCT): 3,000 kelvin
•Colour rendering index: 80 CRI
•Beam angle: 40 degree.
•Luminous intensity: 1552 cd
•Lumen: 615 lm.
•Lumen per watt: 36 lm/w
•Voltage: Mains voltage 240v via LED driver.
•LED driver included: Yes


Any thoughts from our resident 'techies' before i go and blow the childrens inheritance on lighting?

 

[Pford75]

Or the Cree unit which has the following spec...

Warm White, 3000-3500 Kelvin
900 lumens
40 degree beam angle of each LED
12V DC direct input, or use 12V LED no frenquency transformer( driver)

Since this unit is only 15W, but produces 900 lumens....does it follow that this is a much more 'efficient' light?

 

[Penners]

I thought warm white was a bit cooler than that - around 2800 K.

But what do I know...?

 

[MdB]

Since this unit is only 15W, but produces 900 lumens....does it follow that this is a much more 'efficient' light?

Yep, though you have to take into account the losses in any transformer you use. A typical switcher should be over 80% efficient.

 

[Pford75]

Does this unit (Cree) feel like overkill to you? I'm aware that mfgrs exaggerate the 'equivalency' of their LEDs and given the sums of cash involved, I don't want to order a load of the others and find them too dim.

 

[MdB]

The Lumens figure should be a fairly reliable figure to go on as long as you go with a reputable manufacturer. There are all sorts of regs on how it is calculated. On the other hand, take any "equivalent to xxx Watt filament bulb" as those can be exaggerated. Also check that 40 degree is what you want, that is quite a narrow angle spot. Beyond that I can't comment much as I've never bought one nor used one to replace a current bulb.

 

[Flyfisher]

I don't know of any standards for such things but my understanding is that it all depends on how the light from the bulbs/LEDs is 'spread around' to create the overall level of illumination. I think this is the difference between lumens (the light from the bulb/LED and lux (the brightness over an area). Think of a projector; the same bulb will project a very bright image onto a small screen or a dim image onto a large screen.

All a bit complicated when trying to decide on how many LEDs with a particular light angle are needed to adequately illuminate a given area.

This info might help:http://en.wikipedia.org/wiki/Lumen_%28unit%29, as might this extract from that page:
A 23 watt compact fluorescent lamp emits about 1500–1600 lm

http://en.wikipedia.org/wiki/Lux states that:
The difference between the lux and the lumen is that the lux takes into account the area over which the luminous flux is spread. A flux of 1,000 lumens, concentrated into an area of one square metre, lights up that square metre with an illuminance of 1,000 lux. However, the same 1,000 lumens, spread out over ten square metres, produces a dimmer illuminance of only 100 lux.

It also suggests that 50 lux is typical for a "family living room", though an office is given as 320-500 lux.