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What you need as glass (Part V - Standard Zoom)

July 19th, 2011

This is part V of a series of what glass you will need. Each part will discuss a certain lens type and its applications.

Zoom lenses are are rather modern concept that came with the SLRs going consumer. The first zooms had a moderate zoom range and rather small apertures - in film zoom lenses were much more popular and of much higher quality. The marketing was more “Get two (three) lenses in one” appealing to the casual photographer how didn’t carry a bag with all the gear or had different bodies hanging around his neck. Who ever tried to mount a M42 lens while walking quickly sees the benefit.

This class of consumer zooms still exists, but it had been complemented by pro-class zooms that obliterated prime lenses in many applications or even outperforms them.

A standard zoom range is 24-70mm FX or 16-50mm DX, lets start with the consumer grade.

Consumer grade zooms are almost always slower than f/2.8 and/or with variable maximum aperture, on the hand they tend to offer a wider zoom range like 24-120 or 18-105. Image quality of these is OK, but for me they always leave something desired. Beyond the numbers they suffer from poor mechanical quality (plastic mounts are not a big deal, if they break they can be repaired for little money and act as a crash zone for the more expensive parts) slow AF and purple fringing (my theory on this is that this stems from the lens not being truly apo-chromatic).   They are good enough if you just look for a lens that cover x to y, rather compact and reasonably priced.

The recent zooms are all parfocal,  this means once you obtained focus you can zoom without refocusing.

Halfway to the professional grade there are some constant aperture lenses. Canon offers a f/4 L-grade set (hello Nikon, where are you there) of exceptional quality and the third party manufacturers have f/2.8 zooms which skimp a bit on mechanics and optical performance. Tamron/Sigma have a 17-50/2.8 which are good lenses, but when you compare the images with photos take with primes or Gold-Ring/L-glass you see that you get what you pay for.

What is the rave about constant aperture?

This feature is important when shooting with TTL flash while the camera is in manual mode. Many experienced photographers shoot like this: They set the camera to manual and dial in some shutter/aperture/ISO that captures enough ambient light to capture the context. Then the flash is added in TTL mode to freeze motion and light the actual subject. I sometimes went up to a 1/10s  to get enough light in.

If it is rather dark you will still find shooting wide open and set the shutter/ISO for the widest aperture (at the short end) the background will tend to be too dark  on the long end. Remedies:

  • TTL-BL in A or P mode - a bit unpredictable, but OK 80% of the time for standard shots - disable BL with dark backgrounds!
  • Dial in the end aperture so that zooming won’t change the aperture (you loose a lot of light, shooting at f/5.6)
  • Shoot RAW and fix aperture to the max at 1/3 of the zoom range -  correct in post-processing
  • Nikon could add an “E” mode  where the ratio aperture/speed is kept constant - dreaming

Professional Grade

Professional grade zooms start at €1000 (DX) and €1600 (FX). Sigma/Tamron/Tokina (Sigtamina) offer equivalents to a lower price, but none is that “pro” like the original lenses.

The Nikkor/Canons are that good that they can compete with primes. Add the convenience of zooming in the heat of the battle (journalism, weddings) and it becomes clear that their price of four primes covering the range is actually a bargain (24/35/50/85mm)

The choices

For FX the Nikkor 24-70/2.8 is definitely first choice. The lack of VR underlines that this is a professional lens. It is mean to be used with flash/tripod in the hands of an experienced photographer.  Sigtaminas are close second in terms of IQ, distant second in terms of quality/handling. If you can live with that they are worth a look. For DX this range is less than optimal, unless you never shoot wider than 24mm or you plan to get a FX in the next months anyway.

When stepping down  there is the Nikkor 16-85, the Tamron 17-50(VC) and the Sigma 17-50OS for DX. The Tamron/Sigma a 2.8 lenses and I think the Sigma has an edge over the Tamron. The Nikkor is excellent, but slower. Its 5x zoom and fast  AF makes it made the grade.  In FX world you get f/4 lenses 24-120, but these are compromises (Nikon/Sigtamina) the DX segment is better staffed here

The entry grade in FX is almost non-existent (no wonder considering the price of FX bodies), some lenses from film days have survived. For DX there are the 18-55 and 18-105. The Nikkors are not much more expensive than Sigtaminas and better. The 18-55 is a bargain, the 18-105 a bit more expensive, but a big winner when you want to use a polarizer.

Super-zooms

Some year  ago the super zooms like 18-200(DX) and 28-300(FX) came out and they are quite popular. All super-zooms fall into the consumer range, their price almost into the pro grade. If it is really for convenience only the Nikkors are an option. Stay clear from the Sigma/Tamron installements, they are “competitively price”, but the IQ difference really shows in the price tag. The “travel light” argument is void: When travelling you almost never need a tele, unless you are going on a safari. In this case you travel to photograph and adding a dedicated tele isn’t really an inconvenience, is it?

Zoom vs Prime

You can always zoom with your feet -well, not always. Sometimes there isn’t the space to step back to get a group into the frame of you 50mm or perspective distortion forbids taking a portrait, because you happen to have a 24mm lens mounted. When I shoot low-light I carry zoom to get the standard shots and if things a calmer I mount a prime to get some candids. Two different styles of photography, two entirely different lenses. The zooms are the workhorses in a photographers bag.

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