Fixed Focal Length Lenses/"Primes" "Fast" vs "Slow"

[VA_Shooter]

I need some learning. All of my lenses right now are zoom lenses (Nikon 18-35, 24-120 VR, 70-200 VR). I'm thinking about looking into some fixed focal length lenses, lenses that will allow more light to reach the CCD since light seems to be important to the S2 as it relates to sharpness. I have read much here about "primes" but do not understand what a "prime" lens is...can anyone help me out in this regard? I'm also a bit confused about the discussion of "fast lenses" as opposed to "slow lenses." The more I read here every day, the more I learn . . . I really appreciate what the folks here are willing to share. Also, if you had to purchase one or two fixed focal length lenses, which ones would you buy? I'm sort of partial to Nikon lenses, but not necessarily married to them. Thanks for your suggestions.

[Igor]

Hi Connie,
"primes" are fixed focal length lenses: e.g. 10.5mm, 28mm, 50mm, 300mm, etc.

Primes are really better than zooms (in general, tho' there are exceptions of course) in sense of sharpness/color, but zooms are more handy/versatile.

"Fast" lenses mean lenses with lower minimum aperture number or simply with wider opening: e.g. there are two similar lenses 28mm f/1.4 and 28mm f/2.8.
The faster one (f/1.4) costs about $1,200, while the "slow" one is only about $100. In general the faster lenses are better (hense the higher prices).

From my experience I'd recommend you the following primes: 14mm/2.8 Sigma or Tamron, 50mm/1.8 Nikon, maybe 180mm/2.8 Nikon. However I need to know what you're shooting to be more precise.

[deMille]

Good info, Igor.

A few other considerations: Zoom lenses (most) do not maintain the same "effective" aperture throughout the zoom range. This means that your 24-120 set at f8 at 50mm will not be the same real amount of light going through the lens at 120mm.

For in-camera metering, this is not big problem, the exposure system compensates but if you are using studio lighting or otherwise metering manually, you will end up with exposure error. How much depends on your lighting ratio(s), metering technique, focal length setting, etc..

Faster lenses autofocus better. There is more light coming through the lens for the camera to "see" to focus. That is the reason they included the focus light on the camera. It brightens up the subject for a moment, to allow the camera to set focus distance. I have not done specific tests with the S2, but I know that many of the film cameras that staff and myself have used are slightly out of focus (appearing soft) when using slower lenses in low light.

I just talked myself into comparing a few different camera models (digital and film) to see how well they focus with which lens. I'll try to make time and publish the results.

[AndreK]

I kind of have to disagree with the prime vs zoom. Let me just take one of my lenses the Nikkor AF-S 17-35mm f2.8. This is a very expensive lens and covers the

18mm f2.8
20mm f2.8
24mm f2.8
28mm f2.8
35mm f2.8

All of these lenses is twice the price, close in cost and you don't have to change them in the field. And quality, you wouldn't be able to tell the difference. I'm now talking about a fixed aperture through the whole zoom range. Variable aperture zoom lenses would not hold up to the quality.

When you try to focus in low light the faster lenses will let in more light. With slow and fast lenses think of a car going 0-60 in 2.8 second. The lower the number the faster the lens.

What you should buy comes down to what you shoot. I've been shooting everything from birds with 500mm prime and teleconverters up to a 1000mm and on the other side with macro and extension tubes of tiny spiders and other small critters.

Hope this helps in your journey of spending money :)