Looking for low Vf 5mm white

[Marduke]

I am looking for a 5mm white LED with a particularly low Vf. I want to direct drive it off two AA's, so Vf needs to operate from 1.8-3.4v idealy, 2-2.8v would be acceptable. It doesn't have to be bright, this is for LOOONNNGGGG runtime. I just need a single LED for a project. Having a few more for future projects would be nice, but I definitely don't need more than say a 10 pack.

 

[LEDninja]

The original MJLED is the only LED with a known low Vf and can run off Alkaline AAs. The SMJLED will work with alkalines but prefer conditioned L91/L92 lithiums.

Uncut MJLED narrow angle ~25 degrees
http://theledguy.chainreactionweb.com/product_info.php?cPath=48_52_24&products_id=578
Cutdown MJLED wide angle
http://theledguy.chainreactionweb.com/product_info.php?cPath=48_52_82&products_id=568
Uncut SMJLED
http://theledguy.chainreactionweb.com/product_info.php?cPath=48_52_82&products_id=755
Cutdown SMJLED
http://theledguy.chainreactionweb.com/product_info.php?cPath=48_52_82&products_id=754

Available in multiple packs (cheaper per LED)
Uncut MJLED
http://theledguy.chainreactionweb.com/product_info.php?cPath=48_52_24&products_id=834
Others
http://theledguy.chainreactionweb.com/index.php?cPath=48_52_82

 

[billw]

LUMEX claims to have some low voltage SMT LEDs, including Blue at 1.5V:
http://www.lumex.com/product.aspx?id=710

But I don't see either white or 5mm LEDs (their web site is awful!)
(digikey says SSL-DSP5093UWC, with Vf(min)=1.5V, Vf(max)=3.2V...)

 

[Cemoi]

Uncut SMJLED
http://theledguy.chainreactionweb.com/product_info.php?cPath=48_52_82&products_id=755

How do the specified 15 Lumens compare with the 15.5 to 22 cd mentioned on the description on the same website of the Nichia 5mm White - U, and with the 35 cd claimed by DX for the Nichia GS?

According to Wikipedia one candela means 4 PI Lumens if the source is isotropic, which is obviously not the case for a LED.