Olympus SHG 14-35mm f/2 ED — Does It “Cover” more than a Four Thirds/MFT Sensor? (Updated, Camera Obscura)
This is an update to my Sept 19 entry. Somehow I made a measurement error for the image circle (not sure how), thanks to the readers who pointed out my error.
So this time I built a crude camera obscura (tracing paper for the image end), and checked things at 14mm, 18mm, 25mm and 35mm. I had only crude materials to work with, but I can be certain of the results.
The image circle projected by the lens has a soft outline, so precisely where it ends is somewhat ambiguous (stopping down a lens extends the image circle slightly and better defines its edge, but there is no way to stop down the Olympus 14-35mm because it uses an electronic aperture control).
Below is what I measured at infinity focus. Figure ±1mm depending on how one counts the blurry and vignetted edge of the image circle (which can be seen below).
14mm zoom: 26mm image circle 18mm zoom: 30mm image circle 25mm zoom: 32mm image circle 35mm zoom: 32mm image circle (figures below could be off slightly, lens focus indeterminate) Panasonic 25/1.4: 27mm image circle
Panasonic 45/2.8 macro: 25mm image circle
Olympus 45/1.8 ED: 31mm image circle Olympus 75/1.8 ED: 29mm image circle
I also surveyed four other lenses as shown above, but since these have no distance scale or manual focus as does the 14-35mm f/2, where the lens actually was focused is not known, and I also held these by hand to make the measurement (tick marks on the tracing paper every 5mm). So they might be off just a little.
One speculation is that part of the world-class performance of the Olympus 14-35mm f/2 ED on Four Thirds is due to cropping from a central “sweet spot”. But the measurement of these other lenses suggests that an image circle substantially larger than the Four Thirds sensor is the norm, and nothing peculiar to the Olympus SHG lenses.
In theory the 14-35mm f/2 ED could “cover” an APS-C sensor over most of its range excepting the 14mm wide end, but whether the image quality holds up outside the Four Thirds sensor area would have to be seen. Also, the supplied lens shade cuts off portions of the image circle.
|Sensor size||Sensor diagonal|
|Micro Four Thirds, Four Thirds
17.3 X 13.0 mm
23.5 X 15.6 mm
The image below is with the Olympus SHG 14-35mm f/2 ED set at infinity focus at 35mm (at ƒ/2); it is of course upside down in a camera obscura, it has been flipped here.
Projected onto tracing paper, I photographed the image on the tracing paper (taped across a hole in a stiff piece of gatorfoam, cardboard would do also). With something smoother like vellum, perhaps the structure of the paper would intrude less, but the effect is fun nonetheless.