[BioC] GEOQuery - MAS5 normalized data

[Srinivas Iyyer]

Dear group / Dear Sean,
I am using GEOQuery to download a MAS5 (U133Plus2 platform) and intend to make it into a expression matrix and compute differential expression between two classes of samples. 

I have downloaded the data into a gse object.  while making a exprSet object using code in vignette:
data.matrix <- log2(do.call("cbind", lapply(GSMList(gse), function(x) {
tab <- Table(x)
 mymatch <- match(probesets, tab$ID_REF)
 return(tab$VALUE[mymatch])
 })))

Should I log2 values from MAS5 'VALUE'("ID_REF","VALUE","DETECTION.P.VALUE")?

since RMA gives log2 values, I am not sure what MAS5 value means. Could someone suggest a way from here. 

thanks
Srini