Irix 11mm F4 Firefly & Blackstone

Focusing

The Irix 11mm F4 is a fully manual focus lens, but it does have a few tricks up its sleeve. This section will closely ressemble that of the Irix 15mm's review, since the lenses' design and operation are almost identical.

Manual Focus

Given that the lens is manual focus, users will have high expectations for the operation of the focus ring. Just like its 15mm sibling, the 11mm delivers.

The movement of the focus ring is fluid and with good friction, even with the lock completely released. It makes focusing easy and reliable. The throw is long, at 135°. Of this, 10° cover the range from infinity to 1 meter (the same as with the 15mm), and the remaining 125° cover one meter to 0.25 meters. This again gives a high level of accuracy at close distances, and much less at longer distances (where the lens quickly enters the range of hyperfocal distances anyway). The focus ring comes at a hard stop at close distances, and a soft stop at infinity. On our two samples, the distance between infinity and the final, hard stop was slightly different. It is also longer, on both our samples, than what we observed on the 15mm.

The short focal length means that hyperfocal, or something close to it, is comparatively easy to achieve. In particular for distant subjects, the lens mostly allows a "set and forget" attitude. Our comment about the 15mm stands: the designers clearly understood how users were most likely to operate the lens.

The Blackstone and Firefly versions differ in one element: while the former has a ribbed, regular focus ring, the latter has a dotted pattern with a large raised notch. This is a rare feature in lenses both old and new, and genuinely helps to operate the ring. It is something that we wouldn’t mind included on more lenses. It is surprising that only the cheaper version includes this element.

We have observed no difference in the focus operation of the Blackstone and Firefly, as well as between the 11mm and 15mm Irix lenses.

Focus lock

The Irix 11mm (and its 15mm sibling) includes a focus lock. Located above the focus ring, this lock is controlled by turning a second, narrow ring. A quarter turn gets the lens from fully unlocked to fully locked, probably by the simple application of friction. A partial rotation of the lock increases the ring’s resistance and acts as a clamp (like, for instance, on the older FA 50mm macro).

The location of the lock close to the focus ring means that, sometimes, rotating the lock also changes the focus (especially true with larger fingers). We would have preferred more distance between the two rings. The feature is still useful and a rarity. At least the lock is raised higher than the focus ring, helping its operation to some extent.

Infinity focus adjustment

Another differentiating feature of the Irix lenses is the inclusion of an infinity focus adjustment. Described in detail in the online extended manual, this allows the user to tune the position of “infinity” if images set at infinity do not look as sharp as they should. This is done in factory and, in theory, should not have to be performed ever again. If it does need to be done, removing a screwed cover and following the instructions will let the user perform the correction without sending the lens back to the factory. Note that Irix puts a clear warning sign on this cover, and the manual clearly mentions that this adjustment should be performed only if needed.

Verdict

The Irix 11mm is a fully manual lens. Its focus rig is large, well dampened and fluid. Its range allows precise adjustments at close distances, and easy corrections at longer distances.

The inclusion of the focus lock and infinity adjustment are interesting perks. The former is not new, but quite rare nowadays. The latter probably comes from a manufacturing need, which was then transferred to customers as a lens feature. In any case, those elements help operate the lens and achieve precise focus.