Having recently acquired a old enlarger (Opemus iii) as light source for contact printing. also using contrast filters in the process..

HOW much improvement does a proper opal bulb really make ?? Now I'm using a standard 75 w household bulb.. The printing on the bulb has been removed with a dagor77 lens cloth (kitchen scrub :-) How much does the relative hight of the bulb over the condenser head matter for light evenness ??

I will buy a proper lamp (ca 25 USD incl post vs 5USD for a household type) if required, but if not lets use the saving on film??

Any testing which can be done ??