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LED Lighting

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Rhys Sage

pro member
I notice that LEDs are available in white. I recall a time when they were solely red, green or amber.

I also notice people on ebay in China selling packs of 100 5mm white LEDs for about $10. Has anybody tried to build lighting from LEDs?

My only experience of LEDs is the darkroom safelight I built from red LEDs some years ago. It was pretty dim and did the job well. I think LEDs are brighter now.

I do notice that B&H sells LED studio lighting panels. They're horrendously expensive though.

Would the results be good for LEDs if one were to build LED lighting for small product photos? I can see an LED panel would be great to place underneath bottles etc.
 
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Rhys Sage

pro member
Well, I bought a pair of LED spotlight for $17 including P&P etc. They'll fit in the ordinary household lamp sockets so if they turn out to be absolutely awful I can at least use them as closet lights.
 
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Andrew Stannard

pro member
Hi,

Would be interested to hear how you get on with these.

LEDs are certainly a lot brighter now than they used to be. My own experience of white LEDs is limited to head-torches, where they are now used extensively. One thing I've noticed with these though is that they provide a much bluer light than a traditional torch, so might be something to be aware of in a studio setup.

Cheers,
 
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Rhys Sage

pro member
Andrew Stannard said:
Hi,

Would be interested to hear how you get on with these.

LEDs are certainly a lot brighter now than they used to be. My own experience of white LEDs is limited to head-torches, where they are now used extensively. One thing I've noticed with these though is that they provide a much bluer light than a traditional torch, so might be something to be aware of in a studio setup.

Cheers,
Click to expand...

I've seen a lot with a blue tinge but I've also seen them with a creamy colour.
 
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Pablo Montes

New member
Leds

New led technology has increased its average emitted powers since the discovery of the truncated inverted pyramid geometry, The Philips´s SuperFlux and Luxeon models are the ones you should look for this application since they are capable of more than 200lm.

As we all know ideal white light is a combination of ALL the frecuency spectrum. Led however emit by kind of a reversed photoelectric quantum effect and as a quantum fenomena the emit on a discrete set of frecuencies. white LED are engineered so the eye can consider its emission spectra to be white.

I dont know what will happen but i think that for CCD and CMOS sensors results may be different from what you see with your eyes. kind of like fluorecent light.
 
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John Sheehy

New member
Pablo Montes said:
white LED are engineered so the eye can consider its emission spectra to be white.
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I just looked through my diffraction-grating glasses at a small LED flashlight with three "white" (slightly blue) LEDs I have here, and the spectrum is seemingly continuous except right between green and blue there is a small dark band. I was expecting to only see about 4 narrow frequency bands, and was surprised that it was nearly continuous. Many of the spiral flourescent household bulbs, for example, have lots of big frequency gaps.
 
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James Newman

Member
It's nothing to do with photography but I have an anchor light on top of my boat's T-Top that is LED and even though it is very small (about 2 inch diameter) it is visible from almost 2 miles away:)
 
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Rhys Sage

pro member
I went on a shopping trip today - nothing exciting though...

I got a small multiple LED flashlight, a second (more powerful) florescent bulb, black construction paper, a poster frame with perspex/plexiglass (it was cheaper than buying perspex/plexiglass) and some mirror spray.

I already have various other bits and bobs and will do some more product shots maybe on Monday when both stepson and wife are at their day jobs.
 
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Andrew Stannard

pro member
John Sheehy said:
I just looked through my diffraction-grating glasses at a small LED flashlight with three "white" (slightly blue) LEDs I have here, and the spectrum is seemingly continuous
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That's interesting, and like you say somewhat unexpected for LEDs. Did a bit of digging on wikipedia though...

Turns out most 'white' LEDs are actually blue LEDs with a phosphorus coating. The phosphorus is excited by the LED output and in turn produces a much broader spectrum output. Also explains the slight blueish tinge that you can sometime get.
 
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Rhys Sage

pro member
My LED flashlight turned out to be more blue than white. It's usable as a flashlight though and pretty darned good as there's no dead spot in the centre.

The mirror spray was a waste of money as was the poster frame. The perspex was badly flawed and the spray was the same as any spray I could have had elsewhere for 1/3rd of the price.

I haven't tried the bulb nor the construction paper yet but judging by the fact everything else I bought on that trip turned out to be a waste of money....
 
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John Sheehy

New member
Rhys Sage said:
My LED flashlight turned out to be more blue than white.
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These blue-tinted lights are not ideal for digital photography, but not because they aren't truly white. The best light for most digital cameras has an R:G:B ratio of about 1.9:1:1.4, a pinkish magenta. Deep shadow noise has no overall color cast, and all three channels clip at the same level in a white subject, for a maximum full-color DR.

Most of the bluish-looking lights are a bit red-starved; more so than true daylight.
 
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Rhys Sage

pro member
John Sheehy said:
These blue-tinted lights are not ideal for digital photography, but not because they aren't truly white. The best light for most digital cameras has an R:G:B ratio of about 1.9:1:1.4, a pinkish magenta. Deep shadow noise has no overall color cast, and all three channels clip at the same level in a white subject, for a maximum full-color DR.

Most of the bluish-looking lights are a bit red-starved; more so than true daylight.
Click to expand...

I can always do a B/W conversion and then sepia tone. That's very popular here. I have some nice sepia stuff that I've done...

This isn't one of them :p

I had a quick go at this with PSE2 but it needs scratches, folds, torn corners and a better sepia colour.
2837120552_09f68a06d0_b.jpg
 
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Rhys Sage

pro member
My LED bulb arrived from China. It's a little on the blue side but should illuminate a blue or green bottle quite well. I'll have to try some test photos in a day or two.
 
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Pablo Montes

New member
John Sheehy said:
The best light for most digital cameras has an R:G:B ratio of about 1.9:1:1.4, a pinkish magenta.
Click to expand...

I was thinking how would you like if i designed a led lighting circuit trying to put RGB diodes to that particular proportion?

If yes, what would be the other desired characteristics? variable proportion?, battery operation?

I intend it to be a simple circuit so everyone(including me) sould be able to build it at home. Please feedback.
 
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Rhys Sage

pro member
Pablo Montes said:
I was thinking how would you like if i designed a led lighting circuit trying to put RGB diodes to that particular proportion?

If yes, what would be the other desired characteristics? variable proportion?, battery operation?

I intend it to be a simple circuit so everyone(including me) sould be able to build it at home. Please feedback.
Click to expand...

That sounds fun!
 
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