Landscape lens odyssey part I - The benefits of stopping down the aperture

The first post in a series looking at how I arrived at a stable of lenses for my landscape photography as a Canon 1Ds3 owner and dedicated tripod user. 

There is a valid observation that photographers obsess over lens quality, viewing images at the pixel level and ultimately losing sight of the important factors that actually make a compelling photograph. Which is not to denigrate examining an image at pixel level, it can provide feedback on technique, information on the lens character and effect of atmospherics on capturing fine detail. How relevant pixel peeping is on a monitor when images are viewed by the public via a display, book or ideally a print,  I'm not so certain, given the effect of Jpeg compression, ink nozzle diameter and bleed.  Nonetheless, there is compelling evidence on gear forums, where web sized comparisons are posted of images with exif data stripped, from assorted high quality primes, kit zooms etc and the cognoscenti are asked to identify the mystery lenses.  When images are made with wide open apertures there's an impressive hit rate on identifying lenses, when lens apertures are stopped down embarrassment has resulted.  Simply put, many lens optical aberrations and phenomena become more problematic as the physical size of the aperture gets larger and angles of incident light become steeper for marginal and oblique rays of light gathered by the lens.

Optical designers can correct or minimise optical aberrations and phenomena through a combination and selection of optical glass, lens elements, physical size, coatings, tolerances, build etc A comparison of two contemporary lens designs is a perfect illustration of the trade offs in weight, size and cost, to achieve a high level of optical performance wide open.


Zeiss Otus 55mm F1.4 marketed as The best standard lens in the world 
Optical design : 12 lens elements in 10 groups, of which 6 lens elements are made of special glass with anomalous partial dispersion and 1 aspheric lens element.
Weight : 1 Kg
Dimensions : 92.4 mm in diameter and 127.3 mm long without caps.
Focus - manual
Retail price ~ £3,000

Zeiss Otus 55mm f1.4 @ Zeiss

Zeiss Planar T 50mm F1.4 marketed as Reveal the true character
Optical design : 7 lens elements in 6 groups
Weight : 0.38 Kg
Dimensions : 71.3 mm in diameter and 48 mm long without caps.
Focus - manual
Retail price ~ £560

By Tamasflex (Own work) [CC BY-SA 3.0 (http://creativecommons.org/licenses/by-sa/3.0) or GFDL (http://www.gnu.org/copyleft/fdl.html)], via Wikimedia Commons

There is a revealing test online of comparison images made with the Otus and Planar, taken at a series of apertures with a 36mp full frame Nikon DSLR. Scrutiny of full sized Jpegs, revealed to my subjective eyes, that at wide apertures the Otus demonstrates its high optical performance convincingly, whilst the nature of the optical aberrations in the Planar give it distinctive 'drawing style' or 'look'.  Stopped down to F8 and F11 the Planar's optical performance is very respectable in comparison to the Otus.  As the aperture reduces in size i.e is stopped down, the angles of incident light become shallower for marginal and oblique rays of light gathered by the lens and many optical aberrations cease to be an issue.  It emphasises that when considering a lens, landscape photographers need to consider the respective optical performance of a lens when it is stopped down against size, weight, build and price.