Before having my Nikon gear I had a minolta system. Had a 100 F2 lens, Tamron 28-200 and a 50mm. Found out an odd thing when comparing the primes with the zoom. If you set the lenses at the same apeture, even f11 or greater, more light gets in on the prime lenses. This doesn't have anything to do with the speed of the lens but I think it had everything to do with the distance the light has to travel to get to the film plane. The difference my be small but more light was getting in on the primes compared to the zoom. Just one of those weird things that I noticed back when I had prime lenses in my kit. Still want to get a hold of a 100mm range prime. It's a great focal length to have that is easy to handhold and carry around. And most importantly usually sharp as a tack! Just another factoid supporting the great pluses to having a prime lens in the bag!
Odd but true!!
#1. "RE: Prime lenses vs. Zooms" | In response to Reply # 0
#2. "light transmission through multiple elements" | In response to Reply # 0f8bthere Basic MemberFri 26-Jan-01 11:27 AM
I have read that even the best coated lens elements can lose 1 to 2% of the light entering it. When you look at some of the complicated zooms, they can be well into double digits as far as the number of air / glass elements. Even if you went with the best case 1% number, that can cost you 12% to 15% of the light that enters the lens... or more if the coatings are not the best possible quality.
Many optical people talk of T-stop or transmission stop rather than the actual mathematical f-stop. If you are using an auto camera with a stepless shutter, the camera would compensate, adding the required time for the correct exposure. The problem comes when you are using a mechanical shutter where the dialed in speed is what you get, and a separate meter... where f/8 is assumed to really be f/8... not f/9.something.
As a user of primes, I can recommend the Nikon 105mm f/2.5 as a classic design in the range that you are interested in.