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Sigma 14mm F/1.8 Dg Hsm Art

By | 23/11/2022

As an astronomer and science filmmaker, I have been photographing the night heaven and astronomical observatories professionally for more than 10 years. I have photo-documented more than than 30 scientific discipline research sites around the globe in remote places such every bit the South Pole, the Atacama desert, the South African Karoo, and a lab almost 1 mile underground in South Dakota.

For wide-field night-sky photography my principal lens has been the Nikkor 14-24mm F2.8G ED. Its broad, sharp, and rectilinear field of view (FOV) of 114 degrees makes information technology the ideal lens to capture every bit much of the sky as possible in the context of a natural landscape — or equally much of an astronomical telescope every bit possible when shooting inside an observatory. Its wide aperture of F2.8, combined with proficient DSLR performance at loftier ISO, lets one capture features such every bit The Milky Way in a short amount of time, while avoiding or minimizing star trails due to the Globe’south rotation.

When the new Sigma 14mm F1.eight DG HSM Art was appear, it got my immediate attention because of its obvious applications in astrophotography. It’southward 1.three EV faster than the Nikkor lens, which ways an image that needs a 25 second exposure at F2.8 requires just 10 seconds at F1.8. I was able to test this lens on a Canon EOS 5D Marker Iv before this month in Badlands National Park, South Dakota. Here are my offset impressions of using it in the field.

I’ll give you my impressions of using this lens in the field, merely for those who really desire to see the type of images it produces, I won’t brand you lot await.

Photos taken with the Sigma 14mm F1.8 DG HSM Art lens and Catechism 5D Four. Images were processed in Lightroom with no lens correction applied.

Image Brightness at F1.8

First, let’s see how much brighter a scene looks at F1.eight than at F2.8 in these straight-out-of-the-camera (SOOC) images (no vignetting or lens correction practical). Naturally, the increase of ane.3 EV is highly appreciated.

Side by side, let’due south accept a look at some other scene shot at F1.8 and finish down the lens to F2.8 in 1/iii f-end increments while increasing the exposure times accordingly in order to continue the same EV.

This series of images shows an aperture progression from F1.8 to F2.eight in 1/3 f-end increments, while increasing exposure times appropriately in order to maintain the same EV. The right-most image shows the event of applying vignetting correction to the F1.viii image in Lightroom (Corporeality +l, Midpoint 0).

Vignetting and Lens Flares

As one would expect, vignetting is stronger at wider apertures only I like how soft the vignetting gradient is. On site, it was credible how much brighter the image at F2.8 appeared on the LCD screen compared to the one shot at F1.eight. Subsequent assay in Photoshop demonstrated that although the primal portions of the images are equally bright, overall, the image at F2.eight is 27% brighter than the one at F1.8 due to the issue of vignetting. This was hands corrected in Lightroom’s Lens Correction console, albeit more than aggressively than what I would commonly practise.

You can see a lens flare acquired by the off-frame Moon. Although it is pocket-sized and faint, I noticed (anecdotally) that the Sigma lens was more susceptible to the Moon’s glare (when located at very shallow off-frame angles) than the Nikkor lens. You can see the flares in the 100% crops below. Also, notice how much you can reduce star trails by cutting the exposure time to ten seconds. This makes stars announced much closer to pinpoints of lights and makes other astronomical objects like the M4 globular cluster less smudged. Of class, the latter bespeak is relevant depending upon the final size at which the epitome volition be displayed and the altitude at which the image will be seen.

100% crops showing lens flares and star trails (or lack of). The prototype on the left is a 10 sec exposure while the other prototype was exposed for 25 sec. Observe how at x sec the star trails virtually disappear and objects similar the M4 globular cluster appear more clearly.

M4 (the fuzzy patch of calorie-free to the left of its label) is located only 1.3 degrees west of Antares, the brightest star (to the right of its label) in the constellation of Scorpio. M4 is approximately 7,200 light years away, making it ane of the closest globular clusters to u.s.a..

Comatic Aberration

Now, let’due south take a look at the presence of coma, an optical aberration which causes point sources such as stars appear distorted and display a tail (coma) like a comet. This kind of aberration is worst at the widest apertures and, just like vignetting, can exist reduced past stopping down the lens, which might become against the motivation of investing in a fast lens! Therefore, it is very important for a fast lens to exhibit very depression coma.

Beneath are 100% crops of the boardwalk scene shown higher up shot at F1.8 and F2.eight. For such a fast lens, the amount of blackout is very small. In the upper row, notice that at F1.8 coma is only apparent in the bright stars and when the lens is stopped downwards to F2.eight the coma disappears altogether. That is, unless the “star” is extremely bright as it is in the example of planet Jupiter in the lower row. (Click to enlarge.) The upper row shows the tiptop-left corners of the F1.8 and F2.8 images, while the lower row shows the top-right corners. Both sets of SOOC images were exposed for x sec at ISO 1000.

100% crops of the upper corners of the two images shot at F1.8 and F2.viii. Both sets of SOOC images were exposed for 10 sec at ISO one thousand.

Fifty-fifty at F2.8 Jupiter exhibits a significant amount of coma, but this does not concern me much since the odds of having multiple very vivid stars or planets well-nigh the edge of the FOV are not high. Accept in mind, the amount of coma decreases quickly every bit you move abroad from the edges of the FOV. You lot can see this behavior in the following full-resolution images.

In these F1.8 SOOC images you can see comatic abnormality functioning across the entire FOV. In club to evidence point-like stars equally much every bit possible I am including two 10-sec exposures (minimizing star trails), a thirteen-sec, and a 20-sec exposure. To show lens performance as best every bit possible none of the Raw images were processed or corrected in any way. In terms of blackout, these images tin be considered worst-case scenarios since they were all shot at the widest aperture. The results are impressive and, for those interested in seeing a full-frame star field paradigm, I am including one below. (Click to enlarge)

F1.eight, x sec, ISO 200, SOOC F1.viii, 10 sec, ISO 2500, SOOC
F1.viii, 13 sec, ISO 1000, SOOC F1.eight, 20 sec, ISO 3200, SOOC

Boosted Thoughts

Every bit I mentioned earlier, I bask wide-field astrophotography because it lets you nowadays the nighttime sky in the context of beautiful and dark locations effectually the planet. Badlands National Park provides very dark skies over a rugged and fascinating terrain.

My favorite time for doing this kind of photography is near the Kickoff and 3rd Quarter Moon, because yous get moonlight during roughly half of the night. This lets y’all capture the beauty of the mural bathed in moonlight during half of the nighttime and the glorious starlight and The Galaxy during the other half.

Of course, the dazzler of the Badlands doesn’t end at dawn and the combination of daylight and clouds give another dimension to the landscape. The wide FOV of this lens helps you hands capture the vast grass prairies intermingled with sharply eroded buttes and pinnacles. And when these are covered by afternoon stormy clouds you are in for a treat.

You can see some examples that illustrate these things in the gallery at the top of the article.

Time-Lapse Sequences

Another advantage of photographing during the First and Quarter Moon is that you can capture the irresolute light of a moonset or moonrise during a time-lapse sequence. Beneath are three unlike sequences captured with the Sigma 14mm F1.8 DG HSM Fine art, processed in Lightroom, and edited in Subsequently Effects.

Conclusion

Every bit I mentioned, my get-to lens for wide-field astrophotography is the Nikkor 14-24mm F2.8G ED. If I needed to pick simply one lens to photograph the night sky, would I merchandise information technology for the Sigma 14mm F1.8 DG HSM Art? The answer is yep. Although I often use the Nikkor lens at different focal lengths to photograph buildings and monuments (it’south the perfect lens for cathedral interiors), I rarely utilise it to photo the sky at focal lengths others than 14mm. When taking unmarried shots of the night sky (something I ofttimes do while other cameras are shooting time-lapse sequences) the extra 1.three f-stop would allow me to take shorter exposures and use that gained time to creatively experiment with different compositions and angles.

When it comes to taking fourth dimension-lapse sequences of the rotating night sky, you wouldn’t necessarily proceeds much by shortening the exposure time (and acquiring more frames per minute) since yous could end upwardly oversampling the charge per unit of motion of the sky. After all, the idea of time-lapse photography is to speed up time and show things that happen too slowly for us to appreciate. Just it would let you apply a lower ISO and go cleaner images — or a combination of slightly lower ISO and shorter exposure times.

Now, I can see one phenomenon where the wide aperture of F1.8 would allow me shorten the exposure time and increase the temporal sampling of my time-lapse sequence: the Northern Lights! When auroras quickly increase in brightness they besides move faster, and the extra 1.three f-terminate will let me shorten the exposure time by a factor of ii.5 without the need to push the ISO. Or, alternatively, to shoot video of the Northern Lights. I tin can’t wait to try this lens for aurora photography in September. Stay tuned!

The Sigma 14mm F1.viii DG HSM Art lens is available in Canon, Nikon and Sigma mounts. I’m looking forward to hearing your thoughts in the comments department.


José Francisco Salgado, PhD is an Emmy-nominated astronomer, science photographer, visual artist, and public speaker who creates multimedia works that communicate science in engaging means. His Scientific discipline & Symphony films through KV 265 have been presented in 175 concerts and lectures in xv countries.

José Francisco is a seasoned nighttime sky and aurora photographer and filmmaker. If you would like to view, photograph, and learn about the Northern Lights so you can inquire nigh his Borealis Science & Photo Tours in Yellowknife, Canada.

You lot can follow him on: Flickr, Instagram, 500px, Facebook, and Twitter

Source: https://www.dpreview.com/articles/1717621214/astrophotography-with-the-sigma-14mm-f1-8-art-lens