Samyang 10mm F2.8 ED AS NCS CS

Focusing

Ultra-wide lenses such as the Samyang 10mm enjoy an extremely wide depth of field.  Even wide-open, this lens offers a hyperfocal distance of approximately 1 meter, which means that in theory, everything beyond 1 meter will be acceptably sharp when the focusing ring is turned just shy of infinity.  Stop down to F5.6 and your hyperfocal distance is just half a meter.  This means that oftentimes, you can set the focus and then forget about it while you shoot, which is convenient given that this is a manual focus lens.

The Samyang 10mm F2.8 focused for a hyperfocal distance of 0.5m at F5.6 (click to enlarge)

There are two caveats, however. First of all, focusing through the viewfinder becomes extremely difficult when shooting close-ups (objects between 0.24 and 0.5m away) because of the low magnification that this lens offers: your subjects will simply be too small for you to make precise focus adjustments.  Things might even appear to be in focus when they really are not.  We had trouble shooting hand-held close-ups with this lens, and would not recommend it for this purpose- it is simply too wide.

Second, when shooting wide-open, we found that fine-tuning the focus setting was extremely important.  For optimal sharpness at F2.8, you cannot rely on the depth of field or the distance scale. The best thing to do is to use live view to zoom in on your subject and ensure that it's in focus; even this can be a challenge at times due to the small size of objects in the distance.  We recommend using this technique when shooting landscapes as well as subjects that might only be a few meters away from the camera.  A tripod comes in handy.

As for the focusing ring itself: it turns smoothly, stays in place, and has no play or creep.  However, we feel it could have been made a bit stiffer to make micro-adjustments easier.

The Bottom Line

When stopped-down, focusing with the 10mm is rather easy, as you rarely need to worry about the focus setting thanks to the wide depth of field.  This is especially true when you go to use the lens to shoot tight spaces such as the interiors of buildings, cars, or vehicles.  Things only become problematic when shooting close to the minimum focusing distance or at wide apertures.  In these cases, we recommend using live view magnification and a tripod to ensure optimal sharpness, especially when your scene contains fine details.