Irix 11mm f/4 Firefly Review

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  • Very good sharpness
  • CA well corrected centrally
  • Widest rectilinear lens available
  • Very little chance of flare
  • Moisture and dust resistance
  • Well priced
  • Some edge CA
  • Manual focusing via the camera screen very difficult

Irix 11mm F4 Firefly Front Oblique View

It is clear from the moment we receive the classy packaging that this Irix lens is seriously aiming to compete with the best. Nestled within the unusual tin box lies the widest rectilinear (nearly) lens on the market, an incredible 11mm f/4, suitable for full frame Canon, Nikon and Pentax DSLR cameras. There is a choice of Blackstone and Firefly versions, both optically identical and both weather sealed, and here we try out the lighter Firefly version on a Canon EOS 5DS R body. This should be interesting, so let’s look a little more closely at what we have.

Handling and Features

Irix 11mm F4 Firefly Vertical View

A huge plastic snap-on lens hood protects the equally huge, bulbous front element. When in use, this vulnerable front element is protected from impact and from flare by the efficient looking petal lens hood. The hood is fixed and a part of the lens barrel so there is no possibility of using filters. In any event, keeping feet and the photographer’s shadow out of the images is something to watch and a filter mount would almost certainly intrude on the field of view.

This is a manual focus lens and just behind the hood is a locking ring that can be used to fix the focus at a desired position. Immediately behind this is the focusing ring, wide enough to give a good grip and very smooth in operation. On the Firefly version, this also has a raised area to assist grip even further. The distance scale is marked in feet and metres, from infinity down to 0.275m, or 0.9 feet. This is close, but the lens is so wide that initially, it is quite surprising how much is actually included in the frame.

An unusual feature of the distance scale is the inclusion of a Hyperfocal Distance scale. Just lining up the aperture in use with the focus index mark sets the lens to the hyperfocal distance for that aperture. This is a simple and ingenious thought that will be very helpful when seeking to maximise depth of field. It is also useful to set a “snapshot” setting as focusing the lens by eye is well nigh impossible. Modern AF screens do not have the acuity to see the point of focus, and many eyes won’t either. The only real way to focus is to set the scale to the estimated or measured distance. Fortunately, the enormous amount of depth of field allows this to be a practical way to achieve good focus.

There is also a very clear depth of field scale, and an innovative light click stop at the infinity point of the focusing ring, so this can be set even in poor light by feel. The Firefly version of the lens has painted markings, but the more expensive Blackstone has engravings filled with luminous paint, a feature that is really useful in low light.

Finally, the position of the focusing scale can be adjusted as well. Just behind the front of the lens, there is a small access point and by screw adjustment, the position of the focusing scale can be fine tuned for maximum accuracy.

Irix 11mm F4 Firefly On Canon 5dsr

Even the original 15mm f/3.5 lenses of the early 1970s used aspheric elements, so it is no surprise that this 11mm f/4 lens has an optical construction of 16 elements in 10 groups and includes 4 HR (High Refractive Index), 2 ED (Extra Low Dispersion) and 3 Aspherical elements. Neutrino coating helps make this possible, the Irix version of nano coating. 9 rounded diaphragm blades result in a more circular aperture, for improved bokeh.

This is a chunky, heavy lens, the Firefly version weighing in at 783g. There is sealing against dust and moisture, another welcome feature in any lens.

The biggest handling issue, if it is an issue, is likely to be focusing. As mentioned, using the viewfinder or Live View is not really possible, so measuring or estimating distances is a way forward. For most outdoor shooting selecting the hyperfocal distance for the aperture in use works very well. After that, just shoot away, with no need to worry about any further focusing.

Other than that, if you like wide angle lenses then this one is so wide that it opens all sorts of creative possibilities. The wide breadth of sweeping landscapes is incredible, but do watch that there is a strong foreground interest to avoid wide swathes of empty space. It is also necessary to get in close, closer, closer….and still the subject can be too small. The sample images of buildings were shot at incredibly close distances to fill the frame, and, of course, this presents all sorts of challenges regarding perspective and the “drawing” of the straight lines. Things look normal but very wide when the camera back is parallel to the subject, but tilt it even slightly and we enter a new world.

Firefly & Blackstone Comparison Table
Firefly & Blackstone Comparison Table

Firefly and Blackstone versions use the same optics and the same precision, but this table, from the Irix website, summarises the differences.

Irix 11mm F4 Firefly Rear Oblique View


Looking at sharpness, the centre starts off as very good at f/4, becoming excellent at f/5.6 and f/8. Results are still very good at f/11, falling to good levels at f/16 but becoming quite soft at f/22.

The edges are good at f/4, very good at f/5.6 and f/8, good at f/11, becoming soft at f/16 and very soft at f/22.

Irix 11mm f/4 MTF Charts

How to read our MTF charts

The blue column represents readings from the centre of the picture frame at the various apertures and the green is from the edges.

The scale on the left side is an indication of actual image resolution as LW/PH and is described in detail above. The taller the column, the better the lens performance.

CA (Chromatic Aberration) is not easy to correct in such a wide lens, but Irix has done a good job. Centrally, CA is well held to under half a pixel. At the edge CA is visible, but this can be tackled in software. A good result.

Irix 11mm f/4 Chromatic Aberration Charts



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