Irix 15 mm f/2.4 Blackstone review - Focusing

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Irix 15 mm f/2.4 Blackstone

27 September 2016

Arkadiusz Olech

10. Focusing

You set the focus using a comfortable ring which working range amounts to 145 degrees. That value hardly befits a manual lens of good quality – for example the slower Samyang had a ring with a range of 250 degrees and fully manual Zeiss lenses feature rings with 300 degrees of working range. Because of that narrow range the depth of field is also less useful, including marks only by f/16, f/11 and f/8.0; the rivals feature marks even up to f/2.8.

Still it would be hard not to appreciate the efforts of the producer to enhance the comfort of work. You get hyperfocal distance marks, you get an infrared infinity mark and the focus ring can be blocked in any place; additionally you get a tactile click feedback when the ring exceeds infinity. Still you have to keep in mind the fact that the feedback is just an approximate indicator because the precise value of the infinity position depends on the temperature and the length of the wave. On the other hand Irix is the only producer that offers you an opportunity to calibrate the resolution scale on your own so the position on the scale (the mark) and the infinity click always indicate the real infinity for given working conditions.

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It’s also worth mentioning that operating the Irix is really simple. The depth of field provided with such parameters is so high that it forgives a lot – both the errors of a photographer and the narrower working range of the ring. Even at the maximum relative aperture it’s enough you set the focus for a bit over 3 meters and you get sharp images from 1.6 meters to infinity. By f/5.6 you can practically forget about turning the ring at all. Setting it at 1.4 meters ensures you’ll get sharp images from 70 cm to infinity.