In another topic the question popped up whether you would need a clear incandescent light bulb, when only frosted ones are locally available. I managed to find two 25W good old incandescent light bulbs in our house, of which one was clear, the other one frosty.
Here are their spectrum plots:
First the clear incandescent light bulb
Then the frosted incandescent light bulb
And, for you number crunchers, here are more data:
The clear bulb:
Suggested EV @ ISO100 for 1943.5 Lux incident light = 9.6
Closest Planckian temperature = 2638K (DE2K 1.7)
Closest Daylight temperature = 2500K (DE2K 2.5)
Color Rendering Index (Ra) = 99.2 [ R9 = 99.0 ]
R1 = 99.1 R2 = 99.3 R3 = 99.6 R4 = 99.0 R5 = 98.9 R6 = 98.8 R7 = 99.7
R8 = 99.6 R9 = 99.0 R10 = 98.5 R11 = 98.6 R12 = 97.9 R13 = 98.9 R14 = 99.8
Television Lighting Consistency Index 2012 (Qa) = 100.0
The frosted bulb:
Suggested EV @ ISO100 for 1707.7 Lux incident light = 9.4
Closest Planckian temperature = 2576K (DE2K 1.9)
Closest Daylight temperature = 2500K (DE2K 5.3)
Color Rendering Index (Ra) = 99.2 [ R9 = 98.9 ]
R1 = 99.0 R2 = 99.2 R3 = 99.5 R4 = 98.9 R5 = 98.9 R6 = 98.7 R7 = 99.7
R8 = 99.6 R9 = 98.9 R10 = 98.3 R11 = 98.5 R12 = 97.7 R13 = 98.9 R14 = 99.7
Television Lighting Consistency Index 2012 (Qa) = 100.0
Verdict: close enough for everyday use, don’t you agree? However, look at the R9 values. The clear bulb handles the difficult dark red patch a trifle better.
Have fun!
Claes in Lund, Sweden