Lens/image quality and zoom range

[Ryan Hall]

Do lenses with smaller zoom range generally produce higher quality images than lenses with larger zoom range? I am aware that primes tend to produce higher quality images than zooms altogether, so does this trend also apply to zoom lenses?

 

[musicaleCA]

Yup, it does. That's because a lens with a massive focal range (say, 18-200) requires there to be a lot more compromises in the design. The major things tend to be barrel and pincushion distortion; with a shorter range (say 24-70, 70-200, 100-400), it's easier to control those distortions. But going from wide all the way to tele, that presents pretty big problems.

One reason that fixed focal length lenses tend to produce better images for your buck are because they require fewer elements in the design, and the glass is tailored for that particular focal length, so to speak.

 

[Derrel]

I decided to spend 20 minutes comparing the 11x ratio Nikkor 18-200mm VR zoom lens from 2006, by any standard a modern Nikon zoom lens,and one that has two ED-glass elements and three aspherical elements, against a 1980's designed economy 50mm lens with no ED glass and non-aspherical design, against with a 1980's designed 24mm f/2.8 prime lens also without ED glass and also non-aspherical, as well as with a 1990's designed 105mm f/2 prime lens without ED glass and also non-asherical, and a 1990's designed ED glass but non-aspherical 80-200mm f/2.8 pro zoom lens. Compared focal lengths are 24mm,50mm,105 and 100mm, and 200mm.

Nikkor AF-S 18-200mm f/3.5-5.6 G IF-ED VR II DX - Review / Test Report
Nikkor AF 50mm f/1.8 D - Review / Test Report
At the 50mm setting, the more than 15 years newer 11x Nikon 18-200mm VR zoom lens acquits itself well against the economy 50mm prime from Nikon.

Nikkor AF 24mm f/2.8D - Review / Test Report
At f/5.6 and f/8 the 18-200mm Nikon zoom lens is actually a better performer in terms of resolution than the older 24mm prime lens.

Nikkor AF 105mm f/2 D DC - Review / Test Report
Nikon's 105mm f/2 AF-D Defocus Control is a 6 element, 6 group lens. The lens is already very good wide open at f/2, resolving 1,950 LW/PH at the center wide open and around 1710 LW/PH at the edge of the frame at f/2, steadily getting better until at f/4 the 105 prime's performance at the center and edges is almost identical at f/4, f5/6,and f/8 at around 2150 LW/PH at the center and around 2000 LW/PH at the edges at all three f/stops. The 18-200mm zoom lens is probably at its weakest point around 100mm zoom,and it has lost some aperture speed, so at 100mm the wide-open max. aperture is f/5.3, at which aperture the center performance is around 1930 LW/PH, but the edge resolution is only 1225 lw/ph--far,far inferior to that of the prime lens at the edges of the frame. At f/8 however, the zoom lens center figure is 2020 and edge is 1720 or so--respectable. At f/11, the zoom lens is at its best aperture, with center edge figures of 1850/1790, or fairly close center/edge performance.

Nikkor AF 80-200mm f/2.8D ED - Review / Lab Test Report
Comparing Nikon's older, least-expensive 80-200mm f/2.8 ED lens with the new 18-200mm VR lens at 200mm and at apertures of f/5.6, and f/8, the pro f/2.8 zoom lens has marginally higher center and edge resolving ability, and at f/8, the two lenses have almost identical performance in terms of resolving power.

Ken Rockwell has some D200/18-200 VR camera-original files, unprocessed in Photoshop available here Nikon D200 and 18-200mm VR examples
Since the Photozone tests above were ALL performed on the Nikon D200 APS-C camera, looking at his samples might give you a good idea of what a modern, complex, 16-element, $800 11x zoom lens with two ED glass and three aspherical elements can do. Please respect Ken's copyright on these images.