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The yellow-green LEDs, as Jens says, tend to be dimmer. Many of them are
actually phosphor or other down-conversion-process based rather than a
direct LED source. It turns out this is a bit of a tough wavelength to get
direct LEDs for. Part of the problem is sources that use down-conversion
methods tend to be much broader-band than direct LEDs, so not only do you
lose some power from the conversion process, but if you band-filter the
resulting broad spectrum you are throwing away even more light.

Craig

On Thu, Jun 11, 2015 at 11:20 AM, Jens-Bernhard Bosse <[log in to unmask]>
wrote:

> *****
> To join, leave or search the confocal microscopy listserv, go to:
> http://lists.umn.edu/cgi-bin/wa?A0=confocalmicroscopy
> Post images on http://www.imgur.com and include the link in your posting.
> *****
>
> Hi Steffen,
>
> you might find this comparison on Austin Blanco’s blog interesting:
> http://www.austinblanco.com/blog/light-source-shootout-intensilight-photofluor-spectra-heliophor-and-sola/
> From that, the Sola seems to be comparable to the Nikon Intensilight.
>
> If you however go to channel-specific LED sources (fast triggering without
> mechanical filter switching), I can say from my personal experience in
> building such systems that indeed, the 560-590ish LEDs are much dimmer than
> a conventional source in that range. However, one single 470 nm LED (e.g.
> Luxeon Rebel or Cree Xte) can outperform  the conventional easily in the
> blue range. If you look at the typical spectrum of a conventional source
> like the x-cite 120 (
> http://www.aic-imagecentral.com/products/pdfs/LDGIXCite120QBrochure.pdf)
> you can see that it has a dip in the blue range but a peak in the “lime”
> range.
> Hopefully LED technology advances soon such that the gap in the lime range
> is closed.
>
> Best,
>
> Jens
>
>
>
> > On Jun 11, 2015, at 12:49 PM, Steffen Dietzel <[log in to unmask]>
> wrote:
> >
> > *****
> > To join, leave or search the confocal microscopy listserv, go to:
> > http://lists.umn.edu/cgi-bin/wa?A0=confocalmicroscopy
> > Post images on http://www.imgur.com and include the link in your
> posting.
> > *****
> >
> > Dear Listers,
> >
> > we are about to fix the details on the equipment for several microscopes
> for a new core facility. One thing that came up was the excitation light
> source for conventional fluorescence for confocals.
> >
> > I would very much like to switch to LEDs, therefore we consider Lumencor
> "SOLA-SM II - White LED source". An article refered to earlier on this list
> (doi: 10.7171/jbt.14-2502-001 <http://dx.doi.org/10.7171%2Fjbt.14-2502-001>)
> described that light intensitiy of a SOLA is higher over the whole relevant
> than a "120 W metal Halide" lamp (Fig 1,
> http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3970759/figure/F1/), so this
> seemed to be a good choice.
> >
> > I know however heard from two sources that I consider reliable that the
> SOLA has significantly less output in the excitation range of orange and
> near red dyes (maybe 540 to 600) than a EL6000 using a HXP R 120W metal
> halogenid lamp.
> >
> > Therefore I would appreciate if you could share your thoughts on and
> experience with the SOLA, in particular with orange and near red dyes.
> >
> > Thanks
> >
> > Steffen
> >
> >
> > --
> > ------------------------------------------------------------
> > Steffen Dietzel, PD Dr. rer. nat
> > Ludwig-Maximilians-Universität München
> > Walter-Brendel-Zentrum für experimentelle Medizin (WBex)
> > Head of light microscopy
> >
> > Marchioninistr. 27
> > D-81377 München
> > Germany
>