Flash LED question from newbie

[lok1]

Hello All,

I stumbled across your forum after googleing for a while and quickly recognized that you guys know your sh1t when it comes to LEDs. Please help me if you have the time and patience.

I am looking into the theoretical logistics for replacing a xenon flash unit from a point-and-shoot camera with an LED based flash unit. I want to achieve 2-5x the light output of the original xenon unit. I am NOT trying to replicate the lighting power of a hot-shoe mounted flash.

Basically, i want to know...
1) which specific LEDs (Cree/Seoul/Lumiled/other) would be best suited for the application?
2) how many LEDs would be needed?
3) what is the approx unit price per LED and appropriate drivers?
4) would the total volume of LEDs and hardware be similar or less than the xenon flash/capacitor unit?

Thanks in advance for any assistance.

 

[DM51]

Welcome to CPF, lok1.

As your enquiry is principally about emitter output, you've posted it in the right sub-forum. I hope you will get a response. In the meantime, here's a thread that might give you some ideas: Ring of light

 

[HarryN]

Hi, Lumileds makes an LED specifically for that application.

 

[lok1]

hello, is the lumileds LED the Luxeon Flash? i found that one during my research but figured there must be something more powerful that has come out in the last few years... the spec sheets are dated back to 2006. how does the Luxeon Flash compare to the Cree XP for this application?

thanks again.

 

[HarryN]

The "flash" application is somewhat different than other LED applications. You will notice in the data sheet that it is specifically designed for very high instantaneous current and the white light output is tuned for digital cameras. Those specs are somewhat unique, but don't show up as "the brightest" in lumens ratings.

If your goal is more of a continuous "on" application, then I would instead go for using 3 or more monochromatic LEDs which match up to the camera's sensor and do color mixing. The rebels are good for this, as are some other LEDs. The handy feature about the rebels is just how exactly all of the different versions match for optical, mechanical, and electrical properties.

 

[lok1]

for a camera flash application with flash duration between 1-10 milliseconds, is it your belief that 1 or more Luxeon Flash units would be better than 1 or more Cree LEDs or Seoul Semiconductor LEDs? Not having a full understanding of the technical characteristics of LEDs, the only thing i would think to compare is Lumens at max current... but it sounds that you don't think that is an appropriate means of comparison.

 

[HarryN]

Hi, I only played with the flash LED one time, and the testing was limited, so I cannot say, with first hand data, about the exact comparison.

From a data sheet basis, which is reasonable for comparing Cree and Lumileds products, there are some aspects that are useful to compare.

The "flash" application assumes that your application is digital based, not film, which is a reasonable basis given that only a few people like me still use film for "good pictures", even though I use my cell phone camera all of the time for snap shots.

LEDs like an XP-G, Rebel, etc. and their spectral output are built assuming a spectrum to "fool" the eye response curve into "seeing white". This is considerably different than the needs of an RGB digital photo sensor, which does not capture the vast majority of the spectrum, or at least can be more easily supported with relatively narrow spectral lines at R, G and B.

The flash LEDs are designed with a spectrum mostly designed to match the digital sensors vs your eye, so for the eye, they are kind of mediocre in output.

The flash type LEDs are also intended to be used with relatively low continuous power, but high peak power, so the bond wires are also designed to handle this "peak pulse". The bond wires in normal LEDs are mostly designed to handle continuous and less peak. Frankly, they are designed for cell phone distances at parties, so we are not talking about 20 ft range applications.

Since one LED might not be enough for your project anyway, and your "flash" application might need to run more than just milliseconds for a movie like application, then you might be better off just buying R, G and B LEDs that match your sensor, and driving them hard. I have seen some demonstrations of using R, G, Cy and B as well as 6 color mixing that show some technical limitations of the RGB assumptions, but this depends on how sophisticated of a flash you are building.

I would discuss the application with Future (Lumileds distributor) and study the data sheets in some detail vs your light output needs. My experience with Future has been pretty good.

 

[SemiMan]

First off, I would do a search on LED flash...lots of message streams on it here.

2) what are you photographing? If there is movement, no way the LED is going to be anywhere near as effective as the Xenon.

Xenon puts of a ton of light in a very short period of time. Great for stopping motion. LEDS do not even come close in terms of output per unit time. However, if you can live with long exposures... 10's to 100's of milliseconds, then you can achieve more output.

The Luxeon Flash is designed to be small and matched to an optic in a small package. If size if not an issue, Rebel or XPE or XPG will be much better.

Semiman

 

[lok1]

thanks for the advice...i clearly have further research to do.

 

[rollandelliott]

digging up this 7 year old thread. has there been any new led flash technology in the last several years? or is Lumileds still one of the better solutions?

 

[archimedes]

digging up this 7 year old thread. has there been any new led flash technology in the last several years? or is Lumileds still one of the better solutions?

Hi rolland ... bumping very old threads is discouraged on CPF (as the technology changes rapidly) , but we'll let this one run for a bit, since I haven't seen much recent discussion here on this topic and this thread is as good a place as any for it.

However, it is not helpful to post the same or very similar questions in multiple threads, and especially older threads.

Thank you