The electromagnetic form factors for the transition of a Sigma to a Lambda hyperon at low energy 
are calculated using dispersion theory. In this approach we consider the two pion cut of the
transition, in which the imaginary part of the form factors is written as a direct product of the
of the two-pion-Sigma-Lambda amplitudes and the complex conjugate of the pion form factor. A
procedure combining dispersion theory and (NLO) baryon chiral perturbation theory is also used in
computing the two-pion-Sigma-Lambda amplitudes including a two pion rescattering contribution.
It is also found that the inclusion of decuplet baryons in the intermediate state of the transition
is necessary in order to obtain reasonable results, consistent with overall expectations. Through
this approach, the electric transition form factor remains very small while the magnetic form factor
depends strongly on a not well defined low-energy constant of the NLO Lagrangian. The predictive
power of this approach will be enhanced by signicantly constraining this constant from a measurement 
of the magnetic transition radius. Such a measurement can be performed at the future Facility
for Antiproton and Ion Research (FAIR).