Allen is a retired Chemistry teacher and avid Astro and starry sky photographer. His passion for Astrophotography started several months into the first wave of the 2020 Covid pandemic, and now devotes most of his spare time to capturing skies, landscapes and nature.
Having been an avid landscape photographer for most of my life, I now tend to spend most of my time indulging in Astrophotography or as I usually refer to it as “Starry Landscapes”. Starry landscape images are best taken when the Moon is absent from the night sky, making the sky as dark as possible.
The aim for the astrophotographer is to obtain as much shadow detail as possible as well as stars that are round in shape. These images depend upon exposure length and how much light the lens can gather, in other words the size of lens’ maximum aperture. This light-gathering ability is the reason wide-angle lenses are preferred over zoom lenses for Astrophotography. Fast prime lenses offer much larger apertures than zoom lenses of a similar focal length making them better at allowing light to reach the sensor of the camera.
Unfortunately, not every prime lens is capable of producing correctly shaped stars, especially in the corners of the image, when the lens is close to its widest aperture. Often, the corner stars become distorted, usually due to coma distortion or astigmatism, at wide apertures. This is because most lenses are generally designed for daytime use and not usually for photographing stars. For this reason, it can be a challenge for astrophotographers to find lenses that are free or almost free from these distortions. The most popular focal lengths with astrophotographers are 14mm, 20mm and 24mm (35mm equivalent). This is not to say that other focal lengths cannot be used. The 14mm focal length tends to be the go-to “workhorse” lens of the astrophotographer.
I originally owned the SIGMA 14mm F1.8 DG HSM | Art which was the predecessor of this new SIGMA 14mm F1.4 DG DN | Art. The original 14mm F1.8 was certainly the best 14mm lens available when it was released and was immediately sort after by astrophotographers. The lens was a revelation at the time but it was not perfect. At F1.8, the corner stars were slightly stretched due to astigmatism. This star stretching improved by stopping down the lens and had totally disappeared on reaching F2.8. Despite this problem, the lens was extremely sharp across the whole frame and its wide F1.8 aperture made it ideal for focusing manually at night. The lens remained the best 14mm focal length available for astrophotography for many years.
In recent years, SIGMA had released two newly revised lenses, the SIGMA 20mm F1.4 DG DN | Art and 24mm F1.4 DG DN | Art lenses. I had read that these lenses received spectacular reviews by astrophotographers and that they were markedly improved over the previous versions. When I heard SIGMA was revising its 14mm F1.8, I knew it was going to be good. When I read that it was going to be an F1.4 aperture, I was amazed and couldn’t wait to try it out.
SIGMA asked me if I would like to borrow their new 14mm F1.4 DG DN | Art to capture some “starry landscapes” and, needless to say, I was thrilled. The lens arrived at the beginning of August when the nights are longer, ideal conditions for capturing the Milky Way. On opening the box, I was immediately impressed with the quality of the lens’ build. It seemed typical of all SIGMA Art lenses that were always built to a very high standard, feeling strong and durable. The next step was to hope for a clear night sky to carry out some preliminary tests on the lens.
The lens has a few features that are unusual for a wide-angle. Firstly, the lens barrel incorporates a tripod ring. The sort of feature is typically only found on telephoto zoom lenses. This allows the tripod head to be attached to the lens and not to the camera body. The ring is close to the nodal point between the front element and the sensor plane. This is a great advantage when taking panoramas with the lens as it alleviates parallax problems.
In typical British fashion, I had to wait a few nights before the sky was clear enough to venture out to test the lens. My first visit was a very dark site about 8 miles from home. I set my Sony mirrorless camera and the SIGMA 14mm F1.4 DG DN | Art onto a sturdy Gitzo tripod by means of the lens’ tripod foot. The camera and lens balanced beautifully.
The first thing that I noticed was how much brighter the viewfinder image was with the extra light gathered by the F1.4 aperture. This was a big advantage when focusing the lens, after which I engaged the “Focus Lock” switch which disengages the focus ring. As described, I found that no matter what I then did to the focusing ring, the focus of the lens remained totally unaffected. Using this switch meant that there was no need to check lens focus after different sets of images. Brilliant!!
The first opportunity to attempt some astrophotography shortly followed. There was a 77% Moon rising at about the time that I was taking any images. This would make stars difficult to record under these bright conditions. Never the less I set out to Skenfrith Castle in my home county of Monmouthshire.
I began photographing at around 11pm as the moon was rising to my left. I focused on the stars and settled for an exposure of 13 seconds at F1.8, ISO 800. The image looked great on the preview screen but I guessed that at F1.8 there would be insufficient depth of field to keep the castle tower in perfect focus. For this reason, I took a second image with identical settings but focused on the castle tower. The image above (1) shows the result of the two images merged together with a simple mask in Photoshop.
My second excursion with the lens involved a visit to Stonehenge. Conditions were better than Skenfrith (2), as the moon had now shrunk to 34% and the images would be taken well before the moon had begun to rise in the sky. The exposure I used was 15 seconds at F2.2, ISO1600. This shot also required a second image of identical exposure, and focused on the heel stone which is quite close to the perimeter fence.
The third adventure with the lens was a long journey to Carew Castle in Pembrokeshire (3). It was an ideal night for astrophotography as the New Moon was only 1% and nowhere in sight, little local light pollution, completely cloudless night and absolutely no breeze. The exposure that I settled upon was 13 seconds at F1.8, ISO 1600. There was no need for a second exposure this time round as the reflection would be adequately sharp in the star focused image.
The following night, I set off to the Elan Valley (4), the “International Dark Sky Site” near Rhayader in Radnorshire, Mid Wales. The site is a series of man-made reservoirs, built to supply Birmingham.
The area is extremely dark so a torch is essential. I set up my tripod at the northern end of the Valley and opted for an 8 second exposure at F1.4, ISO 3200.
The very first thing that I noticed when reviewing the images straight out of the camera was that there was practically no sign of vignetting in most of the images. Images at F1.4 showed some vignetting, which is expected from any wide-angle lens at full aperture. On stopping the lens down to F1.8, vignetting was barely detectable and by F2 it had totally disappeared. This was very impressive!!
Then the important examination of the corners of the images at 200% magnification to search for poor shaped stars. The results were amazing! Wide open, at F1.4 the stars in the very corners of the image were almost perfect – this is almost unheard of. They were in fact so good at F1.4 that I would have no hesitation in using the lens wide open for astrophotography. The images were also impressively sharp across the whole frame. On stopping down the lens by 1/3 stop, the corner stars were absolutely superb by F1.8.
Well, what is my opinion of this lens? It is magnificent, a real game changer for astrophotography. It enables quality images to be obtained by astrophotographers, even with single exposures. The lens handles and balances beautifully. The Focus Lock Switch is a great time saver. The only “negative” of the lens is its large size and weight! But what would you expect from lens as fast and as perfect as this, you are certainly not going to be able to cut corners with its build. It’s certainly the very best 14mm lens available for astrophotography currently on the market.
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