Before proceeding, this would be a good opportunity to review the in-principle material on aspects of lenses.
There’s much focus (yes – pun) on cameras. Forgivable for a compact, as you buy into the lens as a fixed part of the camera. Nonetheless, even here it is the lens that ought to be driving the buying decision in a major way. That applies with gusto to interchangeable lens systems – the 4/3rds and DSLRs.
Heard of GIGO? (Garbage In, Garbage Out…) Everything your camera does depends on the quality of the image captured by your lens in the first instance. Everything. No amount of hype about a sensor or megapixels can rectify what the lens failed to achieve at the outset – it’s that simple!
Put another way, a superior image will be captured by a superb lens mounted in front of an average sensor (all else being equal). The same cannot be said were the reverse true.
So lens choice is a primary factor in image quality, and ought to be as far as is possible in purchasing decisions.
The reviews of compact cameras on DPReview take lens quality into account for their reviews – rightly so.
For system (4/3rds and DSLR) lenses however, there is a better, more comprehensive on-line resource. Photozone lists by brand most of the popular lenses available. Some of it is a little technical, but never mind the technical terms and absolute numbers used – you’ll get the drift soon enough.
The bottom line is that we would all like lenses that are sharp whether used with large or small apertures, that don’t fall off in quality near the image edges, and don’t cause coloured fringing to appear around the edges of contrasty objects we photograph. If you can empathise with those wants, then go to Photozone and read on!
Some watch-outs with lenses
- Be careful with second-hand lenses unless you know the seller. Try them on your camera (carefully in case the lens mount is damaged). Has it been dropped? Does the aperture function work, with all the aperture blades working together as designed?
- Does the autofocus function work as designed? Is it accurate? If not, can you correct for it adequately in-camera?
- Has it ever been immersed in di-hydrogen monoxide? (steer clear – this is fatal for lenses that are not proofed for this substance**)
- Note also that it is not uncommon for lenses that have been in storage in damp or humid climates to develop mould or fungal growths inside the lens. Good luck getting it out…
- Third party lens-makers like Tokina, Tamron and others generally make quality lenses. Some types of 3rd party lens are made only for certain proprietary mounts (eg Canon only, Pentax only, etc). Ensure that the lens you buy fits YOUR system.
- Lastly, be aware that modern high resolution sensors (especially full-frame) are very demanding indeed of lenses. The 10 megapixel DSLR cameras that were class-leading a decade ago were very forgiving. Not so now. Lenses no longer have anywhere to hide.
PS – Lens is the correct spelling. Lense is an affectation!
** di-hydrogen monoxide = H2O = water… 😉
30 June 2015 – edits, links added