Kinetic spectra of early photolysis intermediates were monitored after nanosecond laser photolysis of a series of artificial visual pigments containing retinal analogs with bulky substituents along the polyene chain. Time-resolved absorbance changes over the spectral range 400-700 nm were recorded at discrete times from 20 ns to 5 mu s following room temperature excitation with a pulse of 477 nm light. Photolysis of bovine rhodopsin regenerated with 9-ethyl-9-cis-retinal, 19,11-ethano-11-cis-retinal, or 13-ethyl-9-cis-retinal produced intermediates similar to those seen after rhodopsin photolysis, i.e. bathorhodopsin (Batho) reversible arrow blue-shifted intermediate (BSI) --> lumirhodopsin (Lumi). In contrast to previously studied artificial pigments and rhodopsin itself, for these chromophores with bulky substituents, the equilibrium between Bathe and BSI is back-shifted. The stability of BSI relative to Bathe is most affected in the 13-ethyl pigment, which had an equilibrium constant of 0.4, approximately one-third of the value observed for rhodopsin. As the bulky substituent moves toward the C9 end of the chromophore, K-eq moves toward the rhodopsin value, with the result for the locked 9-trans-rhodopsin pigment being intermediate between those of the 9-ethyl and 13-ethyl pigments. The presence of bulky substituents also slows the microscopic rate of Bathe decay. This effect is largest for the 9-ethyl pigment whose Bathe decay is slowed by a factor of 5. Freedom of movement of the 9-methyl (restricted in the 9-ethyl case) is proposed to control the rate of Bathe decay in a mechanism involving passage of the chromophore’s C8-hydrogen by the 5-methyl group of its beta-ionone ring to form BSI. For all these pigments, the decay of BSI is substantially slower than for previous pigments, indicating that steric hindrance along the polyene chain interferes with the protein change triggered by BSI formation and suggesting that the protein change may involve side chains adjacent to this region of the chromophore.