  We discuss the choice of the magnetic lattice and parameter optimization of
the fourth generation light source SKIF (Russian acronym for Siberian Circular
Photon Source) under construction in Novosibirsk. The study compares several
basic lattice cells to procure one with low emittance and large dynamic
aperture. The result is a developed lattice of SKIF with 72~pm natural
emittance (at zero beam current and absent betatron coupling) at 3 GeV beam
energy and 476 m circumference. Only two families of sextupoles provide
horizontal and vertical dynamic apertures of 12 mm and 3.5 mm respectively and
energy acceptance more than 5\%. To check the potential of the found solution,
we used slightly modified SKIF lattice to design 6 GeV light source and reached
33 pm natural emittance for 1075 m circumference with 40 straight sections.
Again, only two sextupole families ensure sufficient dynamic aperture (7 mm
horizontal, 4~mm vertical) and energy acceptance more than 5\% for simple
efficient injection and sufficient beam lifetime.
