LED ring lights, use of?


doingthebobs

Link Posted 05/06/2010 - 17:15
Has anybody actually used one of these LED ring lights for macro?

I noticed that there are several past threads, there was a lot of discussion but I wondered if anyone had used one of these and had some pictures to show and comments based on the experience of using one?

I realise that they may not be as good as the proper ring flashes but would they be useful or a waste of money?
Bob

johnriley

Link Posted 05/06/2010 - 17:48
LEDs can be quite blue, are these fully corrected? Also the LED is a point source - does this make the illumination quite harsh and result in lots of point light sources being reflected?

Apart from those questions, it has always looked like a great idea.
Best regards, John

bforbes

Link Posted 05/06/2010 - 18:12
I looked at them a few weeks ago. However I was put off by some manufactures quoting what seemed to me limited length of time the LED's could be illuminated. See link
Barrie
Too Old To Die Young

http://www.pentaxphotogallery.com/artists/barrieforbes
https://www.flickr.com/photos/189482630@N03/

Mannesty

Link Posted 05/06/2010 - 20:59
I haven't looked at any yet, but when I eventually acquire a video enabled DSLR I'd be interested to know if they can be used as a macro video light.

If they are too be of any use, they'd need probably 30 minute runtime as a minimum.
Peter E Smith

My flickr Photostream

bforbes

Link Posted 05/06/2010 - 21:09
Mannesty wrote:
If they are too be of any use, they'd need probably 30 minute runtime as a minimum.

From memory they were only talking about 10 minutes.
Barrie
Too Old To Die Young

http://www.pentaxphotogallery.com/artists/barrieforbes
https://www.flickr.com/photos/189482630@N03/

doingthebobs

Link Posted 05/06/2010 - 21:40
The light colour can surely be taken care of by setting the white balance/post processing.

As for the point source problem, much less of a problem than a high intensity flash tube I would have thought. We seem to have managed that over the years with using diffusers and the like.
I was converted to using LED torches for mountaineering some years ago when I noticed that a friends led lamp did not give the hard shadows on rocky ground that my incandescent lamp did. The light did not give hard shadows that concealed trip hazards in the same way, precisely because it was not a single point source!

Seems strange if the light output is only achieved through wrecking the LED's. Again my led torches stay on for hours with no problems and the battery drain is minimal. One of them specify 140 hours on 3 AAA's! The light output is not the same as a halogen bulb but I don't need to replace batteries and bulb regularly.

I just wondered if anyone had actually tried one of these for macro use. I cannot justify the expense of a ring flash but would like a little help in the illumination department sometimes and it would be handy to know if these things are any use or just a waste of money.
Bob

johnriley

Link Posted 05/06/2010 - 22:18
I have used an LED torch to illuminate underground tunnels. Plenty of light, but very blue as it stands.
Best regards, John

dougf8

Link Posted 05/06/2010 - 22:25
Different LED's have various tints. Head over to CPF to find out.
Lurking is shirking.!

flossie

Link Posted 05/06/2010 - 23:17
LED's are closer to a compact flourescent than a tungsten/halogen source. [*] In particular, they emit a single frequency of light - white LED's are basically Blue/UV LED's that excite a number of phosphers. As a result, you get a very poor spectrum (CRI) from the bog-standard ones found in consumer devices. [**]

Now this spectrum - its really nasty - and to add to the confusion, CRI has proved to be a very bad measurement of their output, as was designed for tungsten sources, and alternative systems of measurements that can cover all the various different types of light sources (tungsten, discharge, flourscent, LED, Plasma) have been proposed but are yet to be widly adopted, so we are left with a problem, you can have "92% CRI" which sounds good, but is actually missing a vital part of the spectrum to look at all comfortable.

Only recently has anyone come out with a handful of LED fixtures that are useable for lighting faces, and they are very low power (compared to the now very high power of RGB units, which are starting to replace Discharge sources).


As for the 10 minute thing - that'll be because that particular device is overdriving the LED's (too much current) which is shortening their life considerably (not that their lives are anything like as high as the marketting drivel claims).


Ooops, long post. sorry. Can you tell all this is related to my day job....


[*] They are also about the same order of efficiency in Lumens/Watt.

[**] You will also get a very nasty big UV spike, which is the subject of a new EU Directive that not many people know about...or that anyone has really figured-out how they are going to deal with it. The HS&E and NPL have been working on trying to address this for the past couple of years - but the simplest solution is to put a UV filter in front of all white LED's.
Still shooting in the dark (literally and metaphorically)...

Anvh

Link Posted 06/06/2010 - 11:13
Here this the spectrum of a "white" led
450 is blue
500 is green
600 is red (roughly)


Stefan


K10D, K5
DA* 16-50, DA* 50-135, D-FA 100 Macro, DA 40 Ltd, DA 18-55
AF-540FGZ

flossie

Link Posted 06/06/2010 - 12:08
That graph is from wackypedia Stefan... so is unsurprisingly misleading - its completely missing the UV spike, I shall see if I can dig one out have got a load of stuff from the NPL somewhere....
Still shooting in the dark (literally and metaphorically)...

Anvh

Link Posted 06/06/2010 - 12:19
flossie wrote:
That graph is from wackypedia Stefan... so is unsurprisingly misleading - its completely missing the UV spike, I shall see if I can dig one out have got a load of stuff from the NPL somewhere....

Yep that's right but all the others are so good as the same on the net, I already looked for it
Lets hope you've something.

As for the UV spike does it really matter, after all the current DSLR cut that light anyway.
At what wave length is the UV spike, i've some drawings down to 200 nm but they don't have a spike.

Not that it's different or anything but it shows it against other light sources.


Stefan


K10D, K5
DA* 16-50, DA* 50-135, D-FA 100 Macro, DA 40 Ltd, DA 18-55
AF-540FGZ
Last Edited by Anvh on 06/06/2010 - 12:24

flossie

Link Posted 06/06/2010 - 14:15
It seems all my paperwork about this is either misfiled or I've leant it to someone. I'll be seeing a collegue this week who definatly will have everything about this issue including graphs from goniometer testing, so will report back in a bit...


Why is this relevant to macro photography? Well a full spectrum is very important or you'll miss details... plus do you really want to expose things to what is basically a laser - what if you were taking a macro photo of an eye?
Still shooting in the dark (literally and metaphorically)...

doingthebobs

Link Posted 06/06/2010 - 14:27
Quote:
plus do you really want to expose things to what is basically a laser - what if you were taking a macro photo of an eye?

I see your point.
Bob

George Lazarette

Link Posted 06/06/2010 - 17:14
Come, come. It's in no way a laser, and certainly not basically.

G
Keywords: Charming, polite, and generally agreeable.
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