Photography: 14mm vs 20mm vs 24mm (pt. 2)

A lens for Nightscape Photography

I love photographing the night sky with the landscape, commonly referred to as Nightscapes. I love shooting these photos really wide because the stars help bring a ginormous sense of scale to the photo. I have been shooting with a basic Rokinon 14mm f/2.8 lens for the last couple years, and while I love it it’s time for an upgrade.

So, I rented three Sigma ART Prime lenses:

  1. 14mm f/1.8: It’s a direct replacement for my existing Rokinon 14mm, I wanted to get a better quality 14mm.
  2. 20mm f/1.4: I wanted to try this lens because I felt that the distortion I was experiencing with 14mm was an aspect of the wide angle, so I got this lens. Additionally, light is really important for nightscapes, so I wanted to try out a faster lens as well.
  3. 24mm f/1.4: I have no intention of purchasing this lens. I rented it because I wanted to compare it to my 24–105mm f/4.0L from Canon. I also have taken a few nightscape shots at 24mm.

The 14mm Comparison

My main goal was to compare the Sigma wide open versus at f/2.8 to that of the Rokinon. I have done heavy research into the ideal aperture before hand, so I knew shooting wide open would introduce coma. That’s also why I was looking at such fast lenses, I knew I’d have to stop down in order to get sharper stars and I don’t want to shoot slower than f/2.8.

Figure 1: Rokinon 14mm vs Sigma ART 14mm wide open

In the photo above I’m comparing the Rokinon 14mm @ f/2.8 (left) to the Sigma ART 14mm at f/1.8 (right). These pictures are 6 minutes apart and the only editing I’ve done was adjust the exposure to ensure they’re as identical as possible.

In the Rokinon the distortion creates these streaks that point towards the corners. It’s easy to mistake it for coma. It may very well be a very strong coma but I believe it’s related to distortion the lenses inability to correct it.

Then we have the Sigma, at f/1.8 we have really obvious coma streaks that appear to go left-to-right, but otherwise the stars themselves appear as really clear points.

Figure 2: The Sigma 14mm at f/1.4 vs f/2.8

Now, when we stop the Sigma down to f/2.8 things get much better. There’s still some coma but it’s tolerable. I took a photo at f/1.4 and posted it to Facebook and the choma is clearly visible. On the other hand, almost everyone is going to overlook it since they’ll either be viewing on a smartphone, or not inspecting the photo very closely.

My 20mm Impressions

I’m going to break from the focus of this article for a bit. I used this lens almost exclusively during my rental period. I loved the field of view this lens provided, the photos looked amazing and the shallow depth of field from the f/1.4 aperture provided a very “Lifestyle Magazine” feel. I went to a friends on Friday evening for a BBQ before we headed out to play with the lenses. The results from this lens feel incredibly natural.

Figure 3: Diptych from the Sigma 20mm @ f/1.4

My impressions with lens continued into the night as we went to go photograph the stars. It still suffered from heavy choma at f/1.4 but it pretty much disappeared when stopped down to f/2.8, much like the 14mm before it.

My Impressions with the 24mm

It’s not a lens I’m going to purchase anytime soon, the fast aperture is amazing but I wasn’t wow’d with this lens like I was with the 20mm. I have a capable 24mm as it stands, and I haven’t been using the lens enough to really warrant an upgrade.

The Trifecta

Continuing the comparison from my last article on this, here I have an overlay of all three focal lengths. The 20mm isn’t that much larger of a field of view than the 24mm; the 14mm is the one to beat. I like 14mm because it gives me plenty of room to crop, to tweak, to skew, and to distort the image so lines are straight and level. As long as I’m aware that I’ll need to leave space around the edges to account for any post-edit cropping and clipping, I’ll be good and any distortion on the edges will be minimized.

The only real advantage a narrower field of view gives me is a full size image with out cropping. If I take a 14mm image but crop it down to 20mm, I no longer have a 20MP image but I don’t find myself ever cropping my images that severely in post.

Now, I have another factor to consider. Cost and Affordability. The 14mm is a whopping USD$1,500 while the 20mm and 24mm are USD$900. I need to really think long and hard if the extra six millimeters are worth the extra $600. Judging by my reactions, the 20mm is the lens I should get. I was impressed with the every day use of the lens and it more-or-less captures incredible nightscapes.

Figure 5: Sigma 20mm @ f/1.4 with obvious choma

So, what am I going to do?

I’m not going to buy any of them just yet. I went in to this expecting to make a purchase either immediately or in a few weeks. I’ll cover this in another article but I’m actually going to go narrower. I have a 50mm f/1.4 and an 85mm f/1.8 lens that I decided to use in my Nightscapes this year. So, I’m going to focus on getting close and personal with our Milky Way this Summer.

When the time comes, I’ll be buying the 20mm though.

Be on the look out for that article soon!

Photography & Technology is my thing.

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