Field Report
by Gary Gray
Some folks prefer primes, others prefer zooms.
If you are looking for a sharp image on a budget, primes are a good bet but are they really sharper than the zoom lenses?
Here, I take a look at two budget primes and two highly regarded zoom lenses and make my analysis.
The 50mm Showdown
Canon EF 50mm f/1.8 II Lens @ $80
vs
Sigma 50mm f/2.8 EX DG Macro Lens @ $269
vs
Tamron SP AF 28-75mm f/2.8 XR Di LD Lens @ $379
vs
Canon EF 24-105mm f/4 L IS USM Lens @ $1,059
Center Sharpness
The crops below are based on the above scene. All photographs were made in bright sunlight with a Canon EOS 5D, from a tripod using mirror lockup and a remote release.The exposure was set for spot metering on the center of the fence in the background, AV control and manual focus mode. Images were recorded using the L-jpg and the faithful color setting.
I manually focused on the spot indicated in yellow above and focus was confirmed by reviewing depth of field in the rocks at the bottom of the scene. I didn't pick a spot exactly in the center of the image, as I consider center sharpness to involve any cross portion of the image where a primary subject may be positioned in the scene.This is a complex scene with plenty of detail, typical of a landscape shot and should provide a real world approximation of what these lenses are capable of resolving in bright sunlight.These crops aren't intended to show everything I looked at when I analyzed the photographs. My intention is to illustrate my personal observations from my review of each photo made by each lens. Each image was compared side-by-side with the other images in Adobe Lightroom at magnifications up to 8:1. My analysis and conclusions are based on these thorough observations.
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| Aperture | Canon EF 50mm f-1.8 | Sigma DG 50mm f-2.8 Macro | Tamron 28-75mm | Canon 24-105 L IS |
| f/1.8 |  |
n/a | n/a | n/a |
| f/2.8 |  |
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n/a |
| f/3.5 |  |
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n/a |
| f/4.0 |  |
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| f/5.6 |  |
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| f/8.0 |  |
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| f/11 |  |
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| f/16 |  |
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| f/22 |  |
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| Center-sharpness conclusions:
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| Aperture | Canon EF 50mm f-1.8 | Sigma DG 50mm f-2.8 Macro | Tamron 28-75mm | Canon 24-105 L IS |
| f/1.8 |  |
n/a | n/a | n/a |
| f/2.8 |  |
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n/a |
| f/3.5 |  |
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n/a |
| f/4.0 |  |
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| f/5.6 |  |
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| f/8.0 |  |
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| f/11 |  |
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| f/16 |  |
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| f/22 |  |
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| Corner sharpness conclusions: Again, we can see here that the Canon ef 50mm f/1.8 is soft up until about f/5.6, and from that point up to f/22 stays pretty consistent and not far from the other three lenses. I also noticed that the Canon 1.8 shows a significant amount of distortion on the edges compared to the other three lenses. CA though is very good on the Canon, maybe the best of the bunch.
Corner sharpness is where the zooms have their biggest problems. It's just difficult to design a zoom lens that can hold it together everywhere at every focal length and aperture. Looking at the two zooms, the Tamron 28-75 is really struggling in the corners up to f/8 and even then it isn't as sharp as the Sigma prime nor the Canon 24-105L. The Canon 24-105 is showing why it is a good zoom lens, as it stays pretty sharp across the board. As we get more stopped down to f/16 the two zooms and the Canon 50mm are about equal, but the Sigma 50mm is still a notch sharper in my estimate. The Sigma does have a slight amount of CA in the corners, but it is as low or lower than the two zooms at most apertures.
Once again, if I had to choose a lens based on corner sharpness, it would be the Sigma 50mm Macro prime. It just holds better sharpness, less distortion and very low chromatic aberration. The Sigma doesn't begin to lose sharpness until f22, at which point the Canon 50mm and the Tamron seem to be on top. Light Falloff / General Open Aperture Images
Light-falloff conclusion: The Canon 50mm prime shows substantial light falloff at f/1.8 but is pretty much cleared up by f/4, and is actually a little better than the Tamron Zoom at f/2.8 The Sigma 50mm prime again shows some light falloff at f/2.8 but by f/4 is clean. The Canon 24-105 is known to vignette at open apertures but by comparison to the two primes and the Tamron at f/4.0, it is right there with them. Oddly enough, the cheapest lens of the bunch, the Canon 50mm f/1.8 prime has the best light-falloff resistance, followed by the Sigma 50mm.
The additional images of the rocking chair are all shot at f/4.0 just to give you the general feel of each lens with an identical shot. Contrast is about the same on each, with the Sigma being a little flatter I think. As you can see, there is very little functional difference with an image size formatted for the internet. For prints up to 8x10, you won't see much difference in any of these lenses. Start printing large format and you'll spot the corner problems with the zooms very quickly compared to the primes. For large prints, I'd avoid the Canon EF 50 II f/1.8 all together at any aperture more open than f8 due to distortion and general softness on the edges.
Final thoughts: Can inexpensive primes compete with quality zooms? You bet, and then some. Based on my comparisons of these four lenses, if I had to chose one lens of the bunch for doing quality landscape photography at 50mm, it would be the Sigma. A close second would be the Canon 24-105L (a lens that costs at about 4 times as much as the Sigma), followed by the Tamron and then the Canon 50mm f/1.8. In defense of the Canon 50mm f/1.8, this lens only costs about 80 dollars brand new and is totally plastic. What amazes me is how well it did compared to a top grade L lens. For what you pay and for what you can expect with image quality, it's a bargain. Would I use it for large format gallery prints...nope...it just isn't good enough.
So, my initial opinions haven't changed. I'll take a good prime lens over a good zoom any day of the week for large format printing. For anything less, just about any lens will do. If a $300 Sigma prime can perform this well, just imagine the quality you can get from the Canon L primes. You're going to pay for it though. If you are looking for an inexpensive and high quality image though, the budget primes are worth the savings and worth investing in. |
