Re: Testing a studio bulb for 6500K

unless you have a spectrometer (i1 pro for example whch you could use with i1Share (free) still works with correct DLLs in Windows7)) the gray card/dslr would be your best bet.
This would be very approximate though as the color temp in dslrs is not that precise.
There is an argument however that the bias light is not all that important as the monitor color temp, especially if following Charles Poynton recommendations for as dark as it gets ambiance plus up to 80-100 nits monitoring to preserve 2.4 gamma