Tuesday, May 28, 2019

50mm EF Lens Comparison: Sigma f/1.4 Art vs. Canon f/1.4 USM - Wide Open

50mm EF Lens Comparison Canon Vs Sigma

Recently at RELATE, we were using the Canon 50mm EF f/1.4 USM and Sigma 50mm f/1.4 Art DG lenses with our EOS R and the EF-EOS R adapter. This got us thinking: are the results really that different?

Therefore, we did a small test with portraiture, which is the type of shot we typically use these lenses for. Camera settings were at 1/125 sec. shutter and ISO 1000, while both lenses were at f/1.4. We've heard that the differences between these lenses are most pronounced when wide open.

This is because the Canon has 7 lens elements, while the Sigma has 13 lens elements. The Sigma includes an aspherical element, which should reduce spherical aberration when wide open. This is the softness that many lenses suffer at large apertures. However, due to these additional elements, the Sigma is twice the size, thrice the price, and three times the weight.

Sigma 50mm Art And Canon 50mm USM

The Canon 50mm EF f/1.4 USM is around $325-350 USD new, while the Sigma 50mm f/1.4 Art DG is ≈$950 USD new.

Therefore, we'll take a couple photos from each lens and compare:

1. The overall look of the photos.
2. Resolution of fine details.
3. Chromatic aberration.

Lens Comparison #1: Overall look

Canon 50mm USM Overall Shot 1
Canon 50mm EF f/1.4 USM (click for full resolution)

Sigma 50mm Art Overall Shot 1
Sigma 50mm f/1.4 Art DG (click for full resolution)

Canon 50mm USM Overall Shot 2
Canon 50mm EF f/1.4 USM (click for full resolution)

Sigma 50mm Art Overall Shot 2
Sigma 50mm f/1.4 Art DG (click for full resolution)

You can click the links in order to view these at full resolution, and I recommend you do so! Towards the center of the frame (which is around Rick's chin) the images are pretty similar. As you move further out, though, the effect of the Sigma's aspherical element allows it to stay sharper. I'll detail this further in the next section, and show some close-ups.

Lens Comparison #2: Resolution of fine details

In this image, I'll start by comparing zooms near the center of the frame. This is where the two should be most similar in terms of fine detail. Again, you can use the links above to see the photos in full resolution, if you prefer.

Canon 50mm USM Detail Shot Chin
Canon 50mm EF f/1.4 USM

Sigma 50mm Art Detail Shot Chin
Sigma 50mm f/1.4 Art DG

As we can see, at the very center of the frame, the lenses are similar, even wide open. Therefore, we'll go a bit further up in the image.

Canon 50mm USM Detail Shot Eye
Canon 50mm EF f/1.4 USM

Sigma 50mm Art Detail Shot Eye
Sigma 50mm f/1.4 Art DG

This is the eye that was slightly further from the camera. Hence, on both images, we're seeing slight blurring due to the extremely shallow depth of field at f/1.4. Still, with the Canon lens we're starting to see the effects of spherical aberration. Here, it manifests as a slight "smearing" of the image. Even so, they're not that far off from each other. The final crop will be much closer to the edge of the photo.

Canon 50mm USM Detail Shot Hair
Canon 50mm EF f/1.4 USM

Sigma 50mm Art Detail Shot Hair
Sigma 50mm f/1.4 Art DG

Here, the difference is most pronounced. On the Sigma shot, the hair towards the foreground is quite sharp, and blurs further back due to shallow DoF. On the Canon lens shot, though, the whole thing is noticeably blurry.

Lens Comparison #3: Chromatic aberration

Our final comparison is chromatic aberration. There are a few points where we'll compare, but this particular type of photo isn't the best to showcase this. This is because there are no objects with sharp edges or a lot of bright points of light. Therefore, this would be more of a concern with still lifes, macro photography, and night shots.

Landscapes and other outdoor photos might have bright points of light and sharp edges, but it's less of a concern there. That's because you'll usually shoot those at smaller apertures, both for deeper DoF and because daylight is so bright.

First, we'll compare the eye highlights.

Canon 50mm USM Eye Highlight Crop
Canon 50mm EF f/1.4 USM

Sigma 50mm Art Eye Highlight Crop
Sigma 50mm f/1.4 Art DG

Chromatic aberration is probably more evident here than anywhere else in the picture. Even so, it's not obvious. The eye glint looks like a white disc with several faint colored discs slightly overlapping. Separating the channels, I found that in this area of the image, blues shifted lower-left, while reds shifted slightly upwards.

The animations below show this crop in each color channel.

Sigma 50mm Art Color Channel Comparison
Canon 50mm EF f/1.4 USM

Sigma 50mm Art Color Channel Comparison
Sigma 50mm f/1.4 Art DG

As you can see, the highlight shifts slightly more on the Canon shot, while the Sigma's highlight stays in place. There is a slight amount of chromatic aberration on the blue channel even with the Sigma, though.

Our next chromatic aberration test is on the edges of shapes. As we mentioned earlier, this will be less noticeable on a portrait. This is because the edges of a face will blur more at a larger aperture. Meanwhile, chromatic aberration is less pronounced at smaller apertures.

Canon 50mm USM Edge Chromatic Aberration
Canon 50mm EF f/1.4 USM

Canon 50mm USM Edge Chromatic Aberration
Sigma 50mm f/1.4 Art DG

While a slight shift of the green channel is visible in this area of the Canon photo, it's relatively mild. Towards the edges of the picture, spherical aberration dwarfs the chromatic aberration effect, so it's harder to tell how pronounced it is.

Therefore, I don't think the difference in chromatic aberration will be a major problem for the majority of photo types. Only specific types of shots would highlight the difference here. For example, if you photographed a stark black-and-white polka dot pattern wide open, it may become noticeable.

After all these tests, we come back to the question: is the difference noticeable? Although I didn't notice much difference at first, after closer examination, it's somewhat obvious. However, keep in mind that these were shot at conditions where an aspherical lens element would make significant difference. At smaller aperture values, the differences between the lenses become less and less pronounced.

Overall, your best bet is to compare these lenses and their potential differences against your needs. Do you shoot at large apertures often, and are fine details and sharp edges all throughout the frame essential? If so, does this outweigh the big differences in price, weight, and size?

If you often travel with your camera, weight and size could be a major consideration. One lens is slightly over half a pound, the other is nearly two, the Canon at 290g and Sigma at 815g.

Sigma 50mm Canon 50mm Front Elements
Note the difference in size of each lens' front element.

In terms of dimensions, the Canon is 2.9" x 2" dia. or 73.8mm x 50.5mm dia. Meanwhile, the Sigma is 3.9" x 3.4" dia. or 99.9mm x 85.4mm dia. This means that the Canon lens takes three-quarters of the volume in your camera bag. This doesn't include lens hoods. The Canon 50mm doesn't come with a lens hood, while the Sigma does. While hoods add bulk to your kit, they're a good idea if you're going traveling. Of course, lens flares can be quite trendy in photography nowadays when used consciously!

We tend to take the Canon lens on trips, but the Sigma is an excellent studio lens with crisp resolution of details.

Hopefully this article, though somewhat limited in scope, was helpful to you!

If you found it useful, you can find my other articles on photography and design here.

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