Clear Lens

Is it required to buy 2 helmets before buying a bike, 1 with clear lens (night time) and dark lens (day time)?
For full face helmets. Are they interchangeable, or will I have to buy 2 helmets? or do they come in transition lenses like sunglasses or somethin?
All full face helmets come with a clear lens, you can purchase tinted like: dark smoke; light smoke; blue, silver, green and other iridium lenses (iridium = mirrored tinted lens) Now scorpion has introduced a transition which they call photocromo lens I haven’t seen any reviews on it and it cost about double what a tinted lens does ($70 and tinted $35).