JPG DCTDecode

Hello All

I have my PS code  using image operator with DCTDecode  as DateSource.

<<

/ImageType 1                   

          /Width 800                       

          /Height 600

          /DataSource   currentfile /DCTDecode filter

               --

               --

>>

image

--------------------------------------

------------------------------------   jpg date

where I insert a High Quality JPG file (4-6) MB to convert the file into PDF with Distiller.

I found the result PDF is very small 150 K, sounds like the PDF has the JPG image very compressed. 

The DCTDecode filter is lossy " meaning that its output is only an approximation of the original input data" as per Red Book

I even used Distiller different job options like Press Quality and even created one with compression turned off but still find the result PDF is much smaller than the original JPG.

Is there any way to control the Quality/resolution/color compression in the result JPG?

Also is there is a way to control the output resolution when deocde the JPG or it will be always 72 DPI as standard PS files?

Regards

Dr. Adam