ELISA 406 vs 493 nm...how to solve - (Jan/22/2014 )

 i was supposed to read the elisa 96 well plate at 406 nm per the alkaline phosphatase assay detection kit but lab does not have that filter. the lowest is 493 nm so i read with that but absorbance values are all maxed out on the plate. 

do i have to get the right filter or is there any other way to get reasonable values without buying new filter? could i decrease concentration or anything? let me know

You probably need to get the right filter, as the wavelength you should read at depends on the compound being evolved by the reaction.  It may be possible to use other wavelengths but it depends on the absorbance (assuming you are doing an abs reading) spectrum of the compound evolved, and how linear the readings will be at that absorbance.