A subjective look at Cosina AF 19-35mm F/3.5-4.5 MC @ Canon EOS 5D. Part 2 — Design and Features. Autofocus

Cosina AF 19-35mm F/3.5-4.5 MC was made in Japan approximately from the late 1990s and up to 2006 for 35mm SLR cameras with Canon EF, Nikon F, Pentax K and Minolta/Sony A mounts. It’s a full frame wide-angle zoom lens suitable for shooting landscapes, architecture and interiors.

The build quality of the lens is definitely good. The lens barrel is painted black (but the lens was also produced in fashionable silver color), made of durable polycarbonate and the mount is metallic. Both the zoom and focusing rings are made of cheaper plastic while the rings of modern lenses are typically rubberized. There are no dust or moisture seals. The lens has a moderate weight of 300 g, maximum diameter of 82 mm and moderate length of 69.5 mm.

The zoom ring is located near the center of the barrel, has width of 15mm, is well damped, rotates smoothly and with proper resistance. The zooming method is rotary. The length of the lens is minimal at focal lengths of ~24-29mm and the front element extends only by 2-3 mm with zooming to 35 or 19mm.

The focusing ring is located near the front of the lens, has width of 10mm, rotates smoothly and has the angle of rotation of only 30-35 degrees. However it is sufficient to perform accurate focusing due to narrow depth of field provided by this lens. There is a distance scale on the barrel of the lens. The front element extends by additional 2-3mm with focusing to the closest distance of 0.5m. In other words, the lens does not have internal focusing (I really don’t think that it’s a serious flaw in this case).

The interval between zoom and focusing rings is only 16-17mm and if you have a big hand and big fingers, then you may accidentally touch the focusing ring instead of the zoom ring and start to rotate it by mistake. Please don’t do it: the ring rotates automatically during autofocus and you can harm the micromotor (built-in for the Canon version of the lens).

Full Time Manual Focus is not supported by this lens (as you probably already realized that). To focus manually, switch the lens to the manual mode using the AF/MF switch located on the lens barrel (at least for the Canon version of the lens).

The front element and the filter thread also rotate during autofocus which does not allow to conveniently use gradient and polarizing filters. The diameter of the filter thread is 77mm — filters of such diameter are usually screwed to the professional and/or expensive lenses. Only the round lens hood of small depth can be used with this lens due to rotating front element. A petal lens hood (for example, one for Tamron or Tokina lenses) will rotate during autofocus and partially block the image.

There’s no aperture ring for Canon version of the lens (the aperture control is fully electronic) but Nikon, Pentax and Minolta/Sony A versions of the lens are equipped with such ring. The aperture has 8 blades, its minimum value is F/19-27 depending on the focal length. «Digital» version of this lens sold by German distributor «Walimex» had minimum value of F/22 despite the focal length (this seems to be the only difference from the original version of the lens).

Optically the lens consists of 13 elements in 11 groups including 1 low-dispersion HLD element to minimize chromatic aberrations and provide great sharpness and contrast even wide open. The front element is slightly convex but allows to use front filters. The proprietary Cosina’s multi-layer coatings are used in optical formula.

The closest focusing distance of the lens is 0.5m — that’s a bit too much and does not allow to make impressive close-up shots.

The buyers of this lens used to get both caps and a round lens hood of small depth (approximately 18mm). The hood can be mounted in reversed position for transportation purposes.

Canon version of the lens is equipped with micromotor. As for the Nikon, Pentax and Minolta/Sony A versions — they rely on in-camera autofocus motor (so called «screw drive»). Canon version of the lens has moderately fast autofocus (but of course it lags behind the lenses with ultrasonic motor). The focusing occupies at worst not more that one second — that’s in case when the focus should be moved from the closest focusing distance to the distance close to infinity (or backwards). However, the specifics of shooting with wide-angle zoom lenses is that most of subjects are located far away, and the autofocus motor in most cases does not need always to move from the closest focusing distance to the distance close to infinity and simply must make only a little step on the distance scale. Therefore, in most cases the autofocus of this lens is instantaneous or takes only a split second!

If you are shooting low-contrast objects (eg, uniformly colored building with no windows), the autofocus can start to hunt from infinity to the closest focusing distance and back and won’t be able to find the right position on the distance scale. Not often, but still it happens. But when shooting in low light conditions, the autofocus always works very reliably and has no problems even with such camera as Canon EOS 5D, which, for some strange reasons, is blamed among the amateurs for alleged «horrific» imperfect autofocus algorithms. No (!) problems with autofocus accuracy of the tested Cosina AF 19-35mm F/3.5-4.5 MC lens were observed on Canon EOS 5D.

The micromotor of Canon’s version of the lens is low-noisy and soon you cease to notice its sounds even when you are the only one person indoors.

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