Many people take pride in their $2000-$4000 camera body. More often than not however, I see people with a really nice prosumer $2000 camera fitted with a $300 subpar zoom kit-lens. The best analogy to this I can think of is buying a super fast Pentium Quad Core fitted with only 512MB RAM running Windows Vista; this is huge component mismatch. Likewise, when you fit a nice camera with a cheap lens, the limiting factor to achieving high image quality is the lens; you're not utilizing the camera to its full potential; most of the pixels will be recording imperfections from the lens. I suspect people use cheap lenses on expensive bodies for the following reasons:
Cheap lenses are lighter. People using cheap lenses don't have to worry about damage/lost.
Yes, these are good reasons to use cheap lenses. If you need something light or compact, by all means buy consumer level (plastic) lenses because they're lighter, and the cost of losing or breaking them or losing them is nearly none compared to owning pro lenses.
Cheap lenses are good enough on a $2000 body.
Noooo! The lens takes in light as input and outputs light on the film, or in these days, a digital sensor. The camera is simply a box that records what the lens sees. If your lens has imperfections, those imperfections will be recorded in the box (film, or digital signals->files). Cheap lenses are full of imperfections, and with a high megapixel camera you will record all the imperfections.
One may argue that in the digital age, you can correct some imperfections using software. This is true for simple to correct imperfections such as vignette. Distortions can be corrected as well, and to some extent chromatic aberrations. However, there are other aspects that are difficult to correct with a badly designed or badly built lens, and in some cases, a corrective procedure may not be desirable or even possible. Below are a list of problems caused by cheap lenses, and the corrective procedure (if any):
- lenses with not enough resolution; the camera film/sensor captures more lines per millimeter (lpmm) than your lens can project sharply. In another word, your lens is too "soft" and can't resolve as many lines as your sensor can. This is as bad as up-sizing an image-- you're not improving image quality. Corrective procedures: downsize your picture (waste resolution) or resharpen (but add noise) or both. Also try stopping down (f5.6-f8) while adding shutter (blur) or ISO (noise)
- lenses with certain tint. Corrective procedures: turn it into B/W. Play with tinting.
- lenses with badly looking bokeh. Corrective procedures: use Alien Skin Bokeh and Photoshop and spend 15-30 minutes per picture... pain.
- slow lenses (with high f-stops) which causes your camera to auto-set the ISO too high (or worse, or that causes your camera shutter to drag). Corrective procedure: not much.
Money is better spent on the body than a lens?
Noooo! A financial metaphor to a camera equipments is that the camera body is like a computer, and the lens is like a monitor. Both will depreciate in time, but the computer will depreciate much faster than the monitor. Like a computer, a digital camera is equipped with the latest bells and whistles and will depreciate 50% in 2-3 years. Next year, there will be a better camera; with higher ISO, more mega-pixel, more FPS for the same price or even less than your camera current one. Moore's Law rules in the digital world.
On the other hand, pro lenses (Nikon gold-rim and Canon L red-rim lenses) do not depreciate as fast. After the 60s and 70s, glass and optics innovations and breakthroughs haven't been as life-changing as microprocessors have been. Sure there were defining moments in integrated lens technology like auto focus, IS/VR, flouride coating, nanocoating, so on so forth, but in general, the field of optics is a very mature field compared to electronics. The laws of optics doesn't change every year like computer does, good glass also retain their values well. Case in point, let's say 10 years ago you were interested in the 80-200mm focal range (and you don't care about size/weight). You could shell out money for a consumer plastic version Nikkor 80-200mm f/4.5-5.6 for $200, or a professional 80-200 f/2.8D for $1200. The professional version is over 1 stop advantage at 80mm, and a whopping 2 stops advantage at 200mm. It's also a lot sharper. Let's say the $1000 price difference is too significant and you end up getting the consumer [plastic] version. After 10 years, you'll have lost many potentially good shots. For example, let's say on stage, a shot that would suffice with a professional 200mm lens with f/2.8 1/200 sec at 800 ISO, now you'll need to use it at f/5.6 at 1/50 sec at 800 ISO on a consumer version. When aperture is open wide on the consumer lens, the image quality is very soft, and the increased in time exposure will usually result in too much hand shake and/or motion.
With this same example, you may be surprised that a pro lens doesn't cost much more than a plastic lens simply because a pro lens will not depreciate much. The true cost of ownership is really the cost of purchase minus the cost of the lens (minus 0-8% transaction fees) when you sell it. Professionals buy and sell all the time. Going back to our examples, after 10 years, you can sell the consumer 80-200mm lens for about $70 on eBay today. On the other hand you can the professional 80-200mm for about $900 on eBay (2008 price). The consumer lens doesn't retain its value well, but the pro lens does. In the end, your final "true cost of ownership" in this example is as follows:
- Consumer Nikkor 80-200mm f/4.5-5.6 initial cost: $200. Selling price: $70. Cost of using the lens for 10 years: $140. High depreciation.
- Professional Nikkor 80-200mm f/2.8D initial cost: $1200. Selling price: $900. Cost of using the lens for 10 years: $300. Low depreciation.
In short, a good quality lens will always retain its values for a long time. It has been that way for decades, and will be that way for as long as the laws of optical physics hold. On the other hand, prices of fancy electronic camera bodies and cheap plastic-feel lenses will drop as fast as computers. They're horrible "investments". A common problem I see today is that people buy nice bodies fitted with a cheap lens. This combination has the worst of both worlds: 1) a cheap lens will not resolve details as well as the body, so megapixels are wasted 2) an expensive body will depreciate 50% in 2-3 years.
1) Cost of lens prices based on observations from historic prices from eBay and CraigsList, and cross referenced with Ken Rockwell's website.
3) More datapoint backfill in 2009:
June 15th 2009 marked the 10 years anniversary of the the first professional Nikon DSLR - the Nikon D1: 2.7 megapixels were selling for $5850 back in 1999 (in 2009 the D1 sells for less than $ 200 on eBay). In 10 years, the price dropped to 3.4% of its original value.