You can use pretty much any type of lamp to pass the calibration. Performing a calibration step does not mean your densitometer is working properly. Calibration means setting your device to a known state -- either right or wrong. There is a reason why some transmission densitometer cost significantly more than the others. The difference is accuracy and repeatability. A lamp must fire at approximately 2,856 degrees Kelvin to meet the ISO/CGAT standards. I doubt very much an off-the-shelf lamp can do this -- You can throw your accuracy out the window. Moreover, the visual filter on your instrument is probably deteriated (Wratten filter). A good transmission densitometer should read accurately between 5.0 density (0.0001% light transmission) to 6.0 density (0.00001% light transmission). There are three models that I know that reads properly in this range. They are: GretagMacbeth D200 II ($2,500.00), X-Rite 361 ($2,400.00) and Ihara T500 ($1,400.00). Good luck!
I am sure that an off-the-shelf lamp is going to affect accuracy. I tried this just to be sure the unit was working before I spent $36.00 on the correct lamp from X-rite. We will see tomorrow when I get the right lamp.