Fish-eye to Normal Prime Lenses on the Pentax K-1

Introduction

In the time I’ve had my Pentax K-1, I have tried a variety of lenses on it, mostly to ascertain which focal lengths I would find useful on it. Due to the cost involved in sourcing new lenses, I have primarily focused on the second-hand market, purchasing stop-gap lenses until I can afford to upgrade. Not only does this lower the cost of experimenting with different lenses, it also allows me to see how well older lens designs can perform on a 36 megapixel sensor.

This post will provide a brief summary of my thoughts on four fixed-focal length lenses, ranging from a fish-eye lens through to a normal focal length lens. Specifically, these are: an MC Zenitar 16 mm f/2.8 fish-eye; an SMC Pentax-A 28 mm f/2.8; a Sigma Art 35 mm f/1.4 DG; and an SMC Pentax 55 mm f/1.8.

MC Zenitar 16 mm f/2.8 Fish-Eye

Up until the purchase of this particular lens, my experience with fish-eye photography had been limited to the Olympus 9 mm f/8 fish-eye body cap lens. Seeing potential for a fish-eye lens in my kit, especially for coastal scenes, I jumped at the opportunity to buy an affordable one with a reasonably good reputation – especially given how much the latest Olympus one costs.

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Daisies in the sand dunes at St. Kilda beach, Dunedin. Photo taken with a Pentax K-1, fitted with an MC-Zenitar 16 mm f/2.8 fish-eye lens. 1/100 s, aperture not recorded, ISO 100.

The first time I handled the Zenitar, I was surprised by how small and light it was. However, the build quality was good, with a tight fit between the components, and a decent grade of metal used throughout. Manual focusing is easy thanks to a well-weighted focusing ring. Since it lacks automatic aperture control contacts, it has to be used with the camera in manual mode, with stop-down metering achieved by the green button. The selected aperture can’t be recorded by the camera, which can cause issues when trying to figure out which camera settings were used.

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Water lapping the base of a stack at Lawyer’s Head, Dunedin. Photo taken with a Pentax K-1, fitted with an MC-Zenitar 16 mm f/2.8 fish-eye lens. 1/200 s, aperture not recorded, ISO 100.

Images from the Zenitar were pleasantly surprising: I didn’t expect them to be as sharp as they are. The sharpness doesn’t reduce excessively towards the edges of the frame, especially at f/5.6-8. Wide-open, there is some noticeable loss of sharpness towards the edges, but the results are still fully usable; I’m excited to see how well this lens performs wide-open when shooting star trails. Colours, especially blues, are very saturated without post-processing, and don’t suffer from any unpleasant casts. Chromatic aberrations are present, but they can be fully corrected, especially from f/4 onward.

SMC Pentax-A 28 mm f/2.8

I’ve always found 28 mm lenses to be quite useful for landscapes; they can fit a lot into the frame, and they don’t exaggerate perspective quite as much as a 24 mm lens. This particular one was also meant to be very compact, so I thought it might be a good option for trips where travelling light is a necessity.

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The University of Otago Registry Building, as seen from the Staff Club. Taken with a Pentax K-1 and an SMC Pentax-A 28 mm f/2.8 lens. 1/40 s, f/8, ISO 100.

The lens is certainly light, even with the accessory lens hood fitted. Build quality is not the greatest, but it isn’t awful, and the plastics used at least feel quite durable. The hood doesn’t clip into place very tightly, and rotates a little; being a rectangular hood, the orientation needs to be checked. Since the hood clips into the filter threads, lens caps can’t be mounted with the lens hood in place. Being as the lens has an “A” position on the aperture ring, it is fully compatible with all auto-exposure modes on Pentax DSLRs; for an old lens, it is quite straightforward to use. Focusing is manual-only, but the focus ring move smoothly, and has a sufficient level of resistance to help with accuracy.

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A tree catches some early evening sun filtering into the Dunedin Town Belt. Captured with a Pentax K-1, fitted with an SMC Pentax-A 28 mm f/2.8 lens. 1/20 s, f/2.8, ISO 100.

Sharpness is sufficient in the centre of the frame with the aperture wide-open, but the image does noticeably soften towards the corners. Stopping the aperture down to f/4 or smaller yields a noticeable improvement in both centre and corner sharpness. Backlighting is not this lens’ strong suit wide open, but performance does tend to improve a bit when stopped down. Colours are handled nicely, although the RAW files lack the punch of those shot with other Pentax prime lenses I’ve tried, and the overall rendition seems a little flatter; it’s not awful, but it’s hardly exciting, either.

Sigma Art 35 mm f/1.4 DG HSM

One of only two brand-new lenses I ordered with my K-1 is the Sigma Art 35 mm f/1.4. I chose it because I know that I find the 35 mm focal length very useful; my most frequently used focal length on Micro Four Thirds is equivalent to 35 mm.Sigma’s Art series 35 mm lens has an excellent reputation for sharpness, so I thought it would be a wise option for landscape use.

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Mist receding over the hills to the southwest of Hoopers Inlet, Dunedin. Taken with a Pentax K-1 and a Sigma Art Series 35 mm f/1.4 DG HSM lens. 1/125 s, f/7.1, ISO 100.

My first impressions on taking the lens out of the box were that it is made from high quality plastics, very well assembled, and supplied with an excellent lens hood. It is fairly large and heavy for a 35 mm lens (in terms of the ones that I have handled to date), although much of this is due to the large maximum aperture. In use, the autofocus is quick and silent, with a well-damped manual focusing ring, and a clutch to allow manual intervention at any time. However, the manual focusing ring does move in the opposite direction to most Pentax prime lenses; this can be confusing when switching between the Sigma lens and Pentax lenses.

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Stars in the sky, viewed from Aramoana, Dunedin. Captured with a tripod-mounted Pentax K-1, a Sigma Art Series 35 mm f/1.4 DG HSM lens, and a remote release. 4 s, f/1.4, ISO 6400

In terms of image quality, this is one of the best lenses I have used. It is very sharp wide open, and improves further upon closing the aperture down. There is some softening due to diffraction at the lens’ minimum aperture of f/16, although the sharpness here is still more than acceptable. Bokeh is generally smooth, unless the background is “busy,” such as direct sunlight filtering through tree branches. I have noticed vignetting at f/1.4, though nothing that can’t be correct in post-processing.

SMC Pentax 55 mm f/1.8

Originally, I’d planned on buying the latest Pentax 55 mm f/1.4 lens. However, upon seeing the price, I decided that a vintage lens was more affordable, and ultimately, the way to go.

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Receding light threw this tree at the Dunedin Botanical Gardens into the shadows. Shot with a Pentax K-1 and an SMC Pentax 55 mm f/1.8 lens. 1/50 s, aperture not recorded, ISO 100.

Being from the original series of K-mount lenses, the 55 mm f/1.8 lacks an auto position on the aperture ring; like the Zenitar, it has to be used in manual mode with stop-down metering. However, it is lightweight, and built to a very high standard, with tight tolerances, and good quality metal throughout the barrel. The focus ring is incredibly light and smooth; it’s the fastest moving focusing ring I have ever used. I managed to locate the optional square lens hood, which is made of good quality plastic, and has a firm mechanism for clipping into the filter threads. However, it means that the lens cap and hood can’t be used at the same time, and filter use is a little more difficult – the hood orientation will need to be checked carefully when using circular polarisers. Like the Zenitar, the 55 mm doesn’t transmit the selected aperture to the camera, making it hard to determine exactly what the camera settings were when reviewing files.

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Growing out of a grassy bank in the Dunedin Town Belt is a tree whose trunk is forked remarkably close to the ground. Shot with a Pentax K-1 and an SMC Pentax 55 mm f/1.8 lens. 1/60 s, aperture not recorded, ISO 320.

WIde open, the Pentax 55 mm f/1.8 makes a good portrait lens, with sufficient centre sharpness, softening towards the edges of the frame, and smooth bokeh, except for areas with fine detail, such as blossoms. Colour fringing in high contrast areas is reasonably pronounced at f/1.8, and can be difficult to fully remove. The same can be said of the colour fringing in harsh light, although the use of the lens hood seems to address this. However, when stopped down to f/4 or smaller, the lens changes character; it is sharp across the frame, making a transition from a large-aperture lens for portraiture to a capable lens for landscape work. One characteristic which does not change with aperture is the colour rendition; colours are rich, and very pleasing, at all apertures.

Final Remarks

Of all the lenses described above, only one has been a slight disappointment: the Pentax-A 28 mm f/2.8. It is certainly capable, but the rendering is not quite as appealing as the other lenses I have tried. This particular lens will be staying on as a compact wide-angle lens for use with my Pentax film bodies, but if a more interesting alternative is found, the 28 mm may well find itself up for sale. The other lenses (the Zenitar 16 mm, Sigma 35 mm, and Pentax 55 mm) will have a permanent place in my lens collection; they are characterful, and perform well, especially when stopped down for landscape work.