The invention provides a negative-acting photoimageable composition comprising A) between about 30 and about 80 wt % based on total weight of A) plus B) of a binder polymer having acid functionality sufficient to render said photoimageable composition developable in alkaline aqueous solution, B) between about 20 and about 70 wt % based on total weight of A) plus B) of an addition-polymerizeable, non-gaseous .alpha.,.beta.-ethylenically unsaturated compound(s) capable of forming a high polymer by free-radical initiated chain-propagating addition polymerization, at least about 50 mole percent of the .alpha.,.beta.-ethylenically unsaturated moieties of B) being methacrylic moieties, and C) between about 0.1 and about 20 wt % based on total weight of A) plus B) of a photoinitiator chemical system, the photoinitiator chemical system comprising between about 0.005 and about 3 wt % relative to total weight of A) plus B) of triphenyphosphine and between about 0.005 and about 2 wt % relative to total weight of A) plus B) of n-phenylglycine.