Venus Optics has made quite a name for itself with its collection of very wide angle lenses, and especially for the Laowa Zero-D series that features optical designs with very little curvilinear distortion. This little 9mm lens isn’t one of the Zero-D range, but it is still remarkable as the widest rectilinear focal length lens available for full frame cameras.
The 9mm F5.6 FF RL lens has an extraordinary angle of view of 135°, so you'll need to be careful your feet don’t make an unscheduled appearance in the bottom of the frame.

The angle of view is so dramatic that users will have to be careful not to appear in their own pictures when the sun is low in the sky.

In fact, checking what is and isn’t in the frame is more important than ever when using this lens as it seems to want to include the whole world. It isn’t just your feet or the things on the ground near where you're standing you have to watch out for – your own shadow, or that of your tripod, can cause quite a problem as well when the sun is low in the sky. This restricts the directions in which the lens can be pointed according to the time of day, and turning the other way to avoid your own shadow will almost inevitably include the sun in the frame.

It took me some time to get in the habit of finding the shadow of something else in which to stand so I wouldn’t cast an obvious shadow on the ground and to begin thinking about composition to take this into account. I actually considered buying a tree costume at one point to disguise my human form. You have to find buildings and trees to block the sun from striking the front element, and if you're recording video, and intending to move around, I recommend doing a practice run to make sure you are in control of the content of the frame is essential.

The lens is nice and small (62.4 x 66 mm/2.45 x 2.6") as well as quite lightweight (350g/12.4oz) given its full-metal body. The aperture ring clicks with stops in each full aperture value with no half or third stop positions, and the distance between F5.6 and F8 is about equal to the distance between F8 and F22.

The focusing ring has a throw of about 90° and is marked in feet and meters from 0.12m (0.4ft) to infinity. The depth-of-field scale suggests that a setting of F22 will allow rendering of 0.19m (0.65ft) to infinity in acceptable focus, and that even F8 will deliver 0.33m (1ft) to infinity – so you may feel focusing is somewhat unnecessary.

The underside of the lens features a tab for finger-focusing the lens. The focus ring turns very nicely indeed, so this tab does provide a useful means of focusing quickly. It is hard to rely on peaking though to find focus without the further assistance of a magnified view, as it can seem that the whole world is in focus as the peaking outlines come to life all over the frame. However, with a good magnified view it is possible to see more clearly what is sharp and what only might be sharp.

With the extensive depth of field of the lens, marks on the front element have a significant impact on the image

The front element is extremely bulbous and protrudes some distance from the main part of the barrel. Although protected in part by the petals of the lens hood it is still quite exposed and a magnet for rain, dust and fingers. With the extensive depth of field of the lens, especially when focused relatively closely, marks on the front element have a significant impact on the image, so it’s particularly important to check it regularly. Sharp-eyed viewers will also notice evidence in the gallery that the sensor of the camera I was using wasn't spotlessly clean – another thing that shows up with an ultra-wide lens.

It isn’t easy to use filters with this lens without the dedicated filter holder from Laowa – and even that isn’t especially easy. It fits over the lens hood and clamps into place. The holder has a striking resemblance to an H&Y filter holder and uses the same magnetic frames and tightening screw. Even though the holder is designed specifically for this lens it needs to be used with caution because if it's misaligned only slightly, or if the holder isn’t pushed back far enough, the filter will appear in the edge of your pictures.

I used the L-mount version of the lens and found the 47MP resolution of the Panasonic Lumix S1R slightly punishing, though when viewed at less than 100% the majority of the images look sharp enough. Resolution in the center of the frame is very good, but it drops off significantly towards the corners.

The lens generally performs better with a close subject, at F8 or F11 and when used on a tripod. Subject motion towards the edges of the frame is also exaggerated, so a faster shutter speed is needed to arrest movement and to produce clean detail.

And if you think you don’t need to pay attention to the focusing ring, you do. The depth-of-field scale is slightly generous regarding ‘acceptable’ sharpness and I found things looked better when I actually focused on the subject rather than relying on all-encompassing hyperfocal distances.

Vignetting, corner smearing and a color shift at the edges are all issues that you should expect when using this lens. Most of the nasties are right at the edge of the frame so it's fairly easy to take them into account when shooting. Trimming the edges gets rid of the worst of the problems and vignetting and the color shift can easily be removed in Raw editing software, leaving a very nice result still with an extreme wide angle view.

Exposure is also tricky when using a lens with such a wide view as no camera system is designed to cope with it

Remarkably, it is possible to achieve some differential focus at F5.6 when focused quite close, and there is a definite depth-of-field progression moving up the aperture range. All the shots in this gallery were taken at F8 or F11, but actually the F5.6 position delivers equal resolution and more light, while diffraction reduces resolution at F16 and F22. Vignetting and chromatic errors are most obvious in the wider apertures and gradually lessen, though by no means disappear, when the lens is stopped-down.

Exposure is also tricky when using a lens like this with such a wide view as no camera system is designed to cope with it. Evaluative/matrix/honeycomb/pattern systems will inevitably be confused when used outside by the range of brightnesses and the areas from which they are coming, so spot and selective metering arrangements work best.

Curvilinear distortion is pretty well controlled considering the angle of view of the lens, but it is still a significant characteristic of the lens. When focused on a distant subject, barreling is generally quite mild, but it increases dramatically at closer focus distances, as shown in the clip above.

The lens is available in mounts for Leica M, Sony FE, Nikon Z and Leica L, and it costs £869/$799. The Leica M version comes in silver or black and costs £979/$899. The optional 100mm magnetic filter holder comes with one set of magnetic filter frame edges and costs £129/$149. For more information see the Venus Optics website.