Another SONY α System: Utilize Mount Adapter(10)

By Junichi Date / CAPA asia

The α7RII can shoot clear images with less color cast, even with lenses for rangefinder cameras


Sony α7RII,
Voigtländer, Super Wide-Heliar II 15mm, F4.5, Aperture priority auto, F8, 1/60 seconds, +0.3 correction, ISO 6400, WB: Auto

Even though old lenses or rangefinder lenses can be mounted, the previous α7R had problems because the pixel pitch decreased with the larger pixel count (36.4 mega pixels). It was difficult to properly capture oblique incident light from the periphery of the image, and a magenta color cast appeared at the periphery. This sort of color cast does not occur with the α7S, which has a low pixel count and a large pixel pitch. Therefore, with the α7R, which has a high pixel count, compatibility was poor with some old lenses and rangefinder lenses.

The α7RII, on the other hand, uses the back-illuminated CMOS sensor, and the number of pixels has been increased over the α7R. Even though the pixel pitch is smaller, the opening of the light reception area is large so oblique incident light can be fully captured. Therefore, even with the Voigtländer Super Wide-Heliar 15mm F4.5 II, with which there was severe color cast with the α7R, color cast is reduced to a level which presents no practical problems with the α7RII. In other words, with the α7RII, it is hard for peripheral color cast to occur, even with old lenses and rangefinder lenses. This is a unique camera which can shoot at a high resolution of 42.4 mega pixels—an extremely attractive choice for fans of old lenses and the Leica M.

At the “Uroko House” an Ijinkan (foreigner’s residence) in Kitano, Kobe. Shooting was done with close attention to horizontal and vertical by using the digital level of the α7RII. Some vignetting is evident, but the lack of distortion aberration is remarkable considering the wideness of the lens.

deal for old lenses thanks to superior performance with oblique incident light

Sony α7R
Color cast at image periphery
Sony α7RII
No color cast at image periphery

In both photos, the Voigtländer Super Wide-Heliar II 15mm F4.5 was mounted, and shooting was done with the lens stopped down to F8. With the α7R, there is a magenta color cast at the periphery, and significant vignetting. With the α7RII, in contrast, there is almost no peripheral color cast, and only mild vignetting. This is the power of a back-illuminated CMOS sensor with superior performance for oblique incident light.

α7R II with back-illuminated full-frame image sensor

Higher resolution, sensitivity, and readout speed
As the world’s first* 35mm full-frame image sensor with back-illuminated structure, this 42.4-megapixel CMOS sensor enhances light collection efficiency, expands circuitry scale, and, with the help of a quick-transmission copper wiring layer, outputs data about 3.5 times faster**, while minimizing image noise to reveal fine details in every picture.

*Among digital cameras with a full-frame image sensor. As of June 2015 press release, based on Sony research.
**In comparison with the α7R.

Previous story: Utilize of Mount Adapter(9)
Next story: Utilize of Mount Adapter(11)

Page Top