Landscape lens odyssey Part V - Divining MTF charts and cinematographers lens evaluation

The 5th 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. 

Canon produces a publication titled 'Lens Work' with a chapter on Optical Terminology and MTF Characteristics, which unusually for texts on optical matters is remarkably lucid in describing what a layman needs to know and one of the few publications that refers to a lens Colour Contribution Index. An ideal MTF chart illustrates the measurements of contrast of an actual lens optical performance under a test environment and can potentially indicate areas of the lens strengths and weaknesses. MTF charts provide no information on colour rendition, flare, distortion and build quality.

A little knowledge is dangerous, as I could appraise Canon's calculated mtf charts with images made by the lenses I owned and observe how the optical performance indicated by the 30 line pairs per millimetre (lp/mm) of the sagittal and meridional curves appeared to correlate with the resolution of fine detail in an image, with the difference between the sagittal and meridional curves indicating astigmatism and a nod to field curvature, astigmatism, chromatic aberration and an assumption my technique was adequate.

It was an exercise that provided an insight into correlating actual performance with theoretical, I'd be lying if I said, I didn't try and visualise what the image might look like if the 30 lp/mm curves were closer together, higher up the %contrast scale and flatter across the image. My eyes also suggested that my copy of the 17-40 was better away from the ends and not that bad focused in the corners and stopped down at 20mm, performance at the tele end was also visibly better when stopped down to f11, which for landscape photography is not a bad thing at all.

Every article I have read on divining mtf charts has a caveat that charts shouldn't be compared with other manufacturers nor across different focal length lenses. It appears that some manufacturers charts are not tests of actual lenses, but are calculated curves; some manufacturers calculated measurements, may be more theoretical than others and may or may not, include design tolerances, assembly tolerances, geometric losses etc. Some knowledgeable commentators hint that a lens could be designed to produce a respectable mtf characteristic that wouldn't necessarily be reflected in actual performance.  So ideally, it would be good if someone independent had the wit to test and measure real lenses and correlate manufacturers MTF charts with reality. It just so happens that a photography website once did just that http://www.photodo.com/browse-lenses/sort-mtf-score-desc and graded lenses to some criteria and also published the actual MTF charts of lenses tested by Hasselblad and the 10, 20 and 40 lpm spatial frequencies at full aperture and f8, at infinity focus. The downside was that the lens tests dated back to 1990's/early 2000's, but they did highlight, to my eyes, some potentially high performing lenses that could be adapted to the EF mount. Just an observation from analysing the photodo MTF's, but if the 40 lp/mm sagittal and meridional curves are above 60% contrast across the image width at f8, there's a high probability the lens is highly regarded in the photography community.

Leica's MTF chart for the Macro Elmarit R 60mm f2.8

Back in late 2011, despite Canon's extensive lens line up, the future in my eyes suggested more image stabilised lenses, faster autofocus motors and a suspicion Canon was focusing on video cameras and cine lenses. So, I decided to look elsewhere for lenses to meet my desired angle of view and optical performance. For a few years EF mount landscape photographers had migrated to Carl Zeiss ZE lenses, legacy 35mm and medium format film lenses that could be mounted on the EF mount by using adaptors. In my opinion there's an entrenched tribalism to photography brands and gear, which unfortunately manifests itself on photography gear forums, as highly subjective opinion based on pseudo science/delusion/personal agendas/prejudice and anecdotal evidence. There are some genuinely useful opinions, but it is a dispiriting search for pearls of wisdom

Leica's MTF chart for the APO Macro Elmarit R 100mm f2.8

Cinematographers were also starting to seriously test and evaluate legacy manual focus 35mm lenses for their needs, their incentive was driven by the price of cinematography lenses and the fact that 35mm DSLR's were incorporating video and increasing capability. The evaluation of legacy and current lenses by the cinematographer community was insightful and informative for its transparency and reliance on characterising a lens performance on actual images under varying subject and lighting scenarios. 

Leica's MTF chart for the Vario Elmarit R 28-90mm f2.8-4.5 @ 70mm

Based upon the manufacturers published MTF correlation with photodo's actual MTF testing and the insights gained from the cinematographer community evaluation, the surprising upshot was that Leica's R lenses would be the ones to further investigate.

Leica's MTF chart for the Vario Elmar 80-200mm f4 @ 135mm

Why?

The southern slopes of the Black Mountains were visited, again.  Which raises the question - why?  The answer is complex.  This area of the Black Mountains has a suite of landforms which appear to relate to phenomena associated with a very cold climate.  Debris from rock slope failures - possibly paraglacial or seismic in origin - appears extensively modified by periglacial processes. More surprisingly, Table Mountain is also thought to be a landslide, resulting from the down wasting of a valley glacier. Both events are thought to have occurred towards end of the Devensian stadial, but there are also alternative theories, it's an interesting wander and the landform suites possibly relate to a number of climatic events.

There are also the insights along the route, from the impact of farming - Ffridd wall, hedge laying, woodland management and relating the the underlying geology with flora. There is also the intangible pleasure of observing the rich tapestry of nature, viz on this trip; a Red Kite shadowed by two Ravens; a Wren foraging in the block slopes; a Fox crossing a distant field; a field conspicuously littered with Mole hills; Fairy inkcaps in a decaying Oak, berry laden Hawthorns, hill ponies grazing, scat on a prominent boulder - the lichen community reflecting a nutrient rich environment and hinting strongly that this boulder has demarcated an animals territory for a while ...

There's also the benefit of stretching the legs and schlepping the photography kit helps puts some debit in the calorific bank, with the festive season calorific binge looming...

Fairy Inkcaps ~ Leica apo macro elmarit 100/2.8

Leica vario elmar R 21-35mm Asph

Then there's the creative itch to be scratched, making a photograph, especially with the quality of light around the winter solstice, when the sun is at its lowest zenith, with a backdrop of broken cloud, rain showers, sunset and with good fortune, there's real potential for atmosphere. The good fortune is light shining through a break in the cloud illuminating the scene. My fortune on this trip was mixed, well broken cloud on the ascent, the first image captures the last light before a hill spur shadow falls across the boulder lobe. The second image has warm but weak sunlight filtered through cloud, the main sunbeam was slightly higher up the hillside, the cloud was failing to breakup sufficiently over the Brecon Beacon massif to the WSW.

Leica vario elmarit R 28-90 Asph

I thought that was the light gone for this trip, the cloud seemed unbroken to the south west, obscuring the sunset and so made my way back across the block slope, as I wanted to look at possibilities for a dawn scenario. On the way some 'Dog Lichens' (Peltigera membranacea) caught my eye.

Dog Lichens ~ Leica vario elmarit R 28-90 Asph

Sunset was a non event, but the cloud was breaking up to the south and dusk provided a display of red/magenta lighting reflected from and diffused by the clouds, a welcome and unexpected bonus. The wind eased too, which was helpful as exposure times were in the order of 4 to 8 seconds duration in the gloaming light.

 Leica vario elmarit R 28-90 Asph 

 Leica vario elmarit R 28-90 Asph 

The opportunity doesn't arise that often, but it is interesting to make images in the colours of dusk, the human eye doesn't pick up the colours as well as the camera sensor and for this trip it was definitely worth waiting around for.