Cleaning fungus in Sigma 50mm f1.4 - Inside the front element

[mark1616]

Hi everyone,

I've just taken my Sigma 50mm f1.4 out of its case after probably 2 years without using and there is some fungus on the inside of the very front element. I've been able to take out the front group of two lenses but can't work out how to separate them to get to the inside of the front one. Does anyone know how to get it open?

Thanks,

Mark