Another SONY α System: Utilize Mount Adapter(1)

By Junichi Date / CAPA asia

In the first article of this series, we take a look at how to master camera settings when using a third-party mount adapter with the α7RII Interchangeable Lens Camera

α7RII with Nikkor lens

The basic knowledge you need to know before using third party lenses and mount adapters is that most of the mount adapters available are simply extension cylinders for converting the mount form. Therefore features like AF and image stabilization will not work, and even aperture cannot be controlled from the body side. Basically, shooting is done after focusing with manual focus, and stopping down to the set F-stop using the lens’ aperture ring.

α7RII has a short flange-back distance, so even lenses with a different mount standard can be used

A distinguishing feature of the α7RII (and other α7 Series), is the short flange-back distance. This is the distance from the mount plane to the imaging plane (sensor or film), and the flange-back distance of the E-mount of the α7RII is just 18.0 mm. In contrast, with a single-lens reflex (SLR) camera, a quick-return mirror mechanism is necessary for guiding light to the phase-detection AF sensor or optical viewfinder, and space is needed to house this mirror mechanism. Flange-back distance is roughly 45 mm for all mount standards: 44.0 mm for the Canon EF-mount, 46.5 mm for the “immortal” Nikon F-mount, and 45.5 mm for the former M42 mount.

A shorter flange-back distance enables a slimmer and more compact camera body. The shorter distance is also advantageous for designing lenses with short back focus (distance from the rear lens plane to the imaging plane), and enables easy design for ultra-wide-angle and wide-angle lenses without any loss of performance.

Also, some mount adapters for the SONY α system are specially designed for APS-C models and these pose a risk of vignetting at the perimeter of the image, so be sure to purchase after checking compatibility with the α7RII.

Many lenses from the film era have a long minimum focus distance, and do not allow shooting from very close up, but some mount adapters have a built-in helicoid. If this type of adapter is used, shooting can be done from a position closer than the lens’ original minimum focus distance.

α7R II with back-illuminated full-frame image sensor


LENS COMPATIBILITY: Sony E-mount lenses
SENSOR: 35mm full frame (35.9 x 24.0mm), Exmor R CMOS sensor
ISO SENSITIVITY: Still images: ISO 100-25600 (expandable to ISO 50–102400 for shooting still images), AUTO (ISO 100-6400, selectable lower limit and upper limit), Movies: ISO 100-25600 equivalent, AUTO (ISO 100-6400 equivalent, selectable lower limit and upper limit)
BATTERY LIFE (CIPA, STILL IMAGES): Approx. 290 shots (viewfinder) / approx. 340 shots (LCD screen) (CIPA standard)
VIEWFINDER TYPE: XGA OLED, 1.3 cm (0.5 type) electronic viewfinder (colour)
SCREEN TYPE: 7.5 cm (3.0-type) TFT drive
DIMENSIONS (W X H X D): 126.9 x 95.7 x 60.3 mm
WEIGHT: 582 g (Body Only) / 625 g (With battery and media)

Product Review: Sony α7R II

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Next story: Utilize Mount Adapter(2)

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