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Three Way Shootout Part 2: Resolution

Dustin Abbott

April 13th, 2015

Red vs. TungstenThis article will seek to examine what is probably the single biggest burning question for us all:  can the Tamron SP 15-30mm f/2.8 Di VC USD live up to the superlative standard for sharpness (particularly in the corners) set by the Canon EF 16-35mm f/4L IS?  I first want to give a shout-out to Tamron of Canada (Amplis Foto) for providing the copy of the Tamron for this comparison and B&H Photo of New York for providing the 16-35mm f/4L IS and the 16-35mm f/2.8L II for this comparison.  The copy of the Rokinon 14mm f/2.8 that I use for comparison was purchased from the great people at Amplis Foto a few years ago.  Reward these companies that provide the answers to your questions by shopping there.  Back to the question of whether or nor the Tamron can optically compare to the Canon…

Before answering that question, let me first say this:  There is only one loser in this comparison, and that is the Canon EF 16-35mm f/2.8L II. It tells its age in many ways, including very poor performance in the corners, noticeably inferior contrast (even stopped down), poorer flare resistance, and much more chromatic aberrations (both green and purple fringing).  One thing that I have learned as a reviewer and one who actually does photography with a huge variety of lenses is that field use is kinder to many lenses than chart testing.  Some lenses don’t chart very well, but compensate by producing good pictures when actually used.  Some of you may own the EF 16-35mm f/2.8L II and probably have produced some stunning photos with it.  I have certainly seen a number of amazing images from it.  If you own it and like it, then just go on enjoying it; the existence of these other lenses doesn’t make yours worse!  I have had to the same thing with my EF 135mm f/2L despite its optical performance being passed by both the Zeiss APO Sonnar T* 2/135mm and the Samyang 135mm f/2 ED UMC.  But when this lens has to go head to head with the new Canon or the new Tamron, it comes away looking pretty bad by comparison (with a few notable exceptions that will show up in the next articles).  When I took it and f/4L IS out I could definitely tell a difference between the images.  The difference was immediately noticeable when comparing images, as both the sharpness and contrast differences (along with chromatic aberrations) were quickly apparent.

Not so with the Tamron and the f/4L. These are both amazing optical instruments. There is a bit of give and take:

  • The Canon has better chromatic aberration control (almost none). The Tamron has very little, but more than the Canon.
  • The Tamron is much better in the vignetting department, with noticeably less shading in the corners. That difference is even more apparent when it is stopped down to f/4.
  • The Canon is marginally sharper in the extreme corners, with the advantage virtually gone by the time the Tamron is stopped down to f/4.
  • The Tamron produces slightly more micro-contrast.
  • The Tamron (obviously) produces a more blurred background at or close to minimum focus.
  • The Tamron (surprisingly) has less distortion.

Most of these differences, however, are only distinguishable by comparing images taken in controlled environments side by side.  In fact, it is very hard to distinguish images taken by these lenses from each other except if they are shot with narrow depth of field (the f/4 backgrounds are a little busier due to the smaller aperture). The color rendition is quite similar. There were a few situations where the Canon had some motion blur because it would drop to a lower shutter speed due to the slower maximum aperture, but under normal circumstances I would just raise the ISO to compensate. This is really only an issue if you are a low light situation where that isn’t an option.

In subsequent articles we will look closer at:

  1. Angle of view
  2. Distortion
  3. Coma and shooting the stars
  4. Bokeh
  5. Flare Resistance
  6. Handling

This article is going to take a closer look at resolution, however.  The best way to visualize this comparison is by watching the video below where I go through the process of acquiring the images and then interactively look at the results.  I think you will find this very interesting:

None of these images have received any processing or correction.  I shot them as RAW images so that there would be no in camera processing.  There is not additional sharpness, chromatic aberration correction, distortion correction, or vignette correction.  As you can see, the optical difference between our two top competitors is marginal.  Both the Tamron and the Canon f/4L IS offer extremely impressive resolution.  If you would prefer to do this comparison yourself, here are the full size images of the Tamron at f/4 (top) and the Canon EF 16-35mm f/4L IS at f/4 on the bottom – if you will click through you can go to a page with the full size images that you can zoom into at any point.  One thing to note:  the focus point was the poles in the center of the image, which means that at this aperture the bottom corners (and bottom quarter of the image) are not yet in focus, so don’t draw any conclusions on any of the lenses from that.

Tamron f-4Canon f-4

Here are the pertinent crop comparisons.  In this series, the Tamron is on the left (as marked) and the Canon is on the right.  Other than the heavier vignetting of the Canon and a minute amount of additional fringing on the Tamron, making a visual distinction between the lenses is difficult.  I do think the extreme left still slightly favors the Canon, but every other portion of the image is a draw.

As a final comparison, here is the f/4 image from the older Canon EF 16-35mm f/2.8L II:

Canon II f-4You can quickly see that the newer lenses outresolve the older f/2.8L lens in a dramatic way.  That is particularly true in the corners, but is true throughout the frame as well.  The older lens also demonstrates far more chromatic aberrations and reduced contrast.  If you want to look further, I am including 1500px copies from the Tamron at 15mm, 20mm, and 30mm in f/2.8, f/4, f/5.6, f/8, and f/11.

This second series will share similar images from the Canon EF 16-35mm f/4L IS (f/2.8 results won’t appear for obvious reasons):  16mm, 20mm, and 31mm in f/4, f/5.6, f/8, and f/11.

The third series shares the images from the Canon EF 16-35mm f/2.8L II:  16mm, 21mm, and 31mm in f/2.8, f/4, f/5.6, f/8, and f/11.

Our final series is from the Rokinon 14mm f/2.8.  These images (for obvious reasons) are only at 14mm:  f/2.8, f/4, f/5.6, f/8, and f/11

It may be harder to visualize the differences in these images, so let me summarize my findings: at 15/16mm for the Canon f/4L and Tamron further stopping down is just about either getting a slightly deeper depth of field or because you want a slower shutter speed:  they are both essentially perfect sharp at f/5.6 and sharpness doesn’t change at f/8 or f/11.  f/5.6 is probably a great aperture to choose for landscape work, as it represent something close to peak sharpness across the frame.

As for the Rokinon, it suffers in this comparison for a few reasons.  The incredibly heavy vignetting really detracts from the image quality here, but note that this is very easy to correct for in post.  The Rokinon also suffers because of its fairly extreme distortion that stretches the edges of the image and gives the appearance of softness.  Towards the center of the image it is fairly equal to the other competitors, but is definitely the worst in the extreme corners.  Stopped down and corrected it continues to offer great image quality at its bargain price point, but it is not at the level of our top two performers.

At 20mm most of the previous observations remained true, although the Tamron looked better in the corners than the Canon f/4L while the Canon looked better in the center (essentially reversed, which could be a focus variation).  When stopped down to f/5.6 and beyond the images were indistinguishable from each other.  The older Canon continued to lag behind the other two lenses in an equally obvious way.  Test say that the Tamron is actually the sharpest option available in the 21-24mm range.

A 30mm the older Canon seems to fall behind even further.  It is quite soft wide open even towards the middle of the frame when compared to the other two.  The Tamron is now basically equal to the Canon f/4L even wide open at f/2.8.  Both of these lenses are producing a nearly flawless result, however, with great resolution across the frame and excellent contrast.

(Believe it or not, there are a couple of places in later discussions where the older Canon f/2.8 II is a winner, but resolution and overall image quality is not one of them.)

Put simply, while I do feel that there is a very marginal advantage at wider apertures for the Canon EF 16-35mm f/4L IS (at least at 16mm), you can take resolution off the table as a means of making your decision between the new Tamron 15-30 VC and the Canon 16-35mm f/4L IS.  In subsequent articles were will compare the differences in other areas that might help you make that decision one way or another, but I don’t think that you can declare a clear winner between these two new wide angle zooms when it comes to resolution…unless you need an f/2.8 aperture.  The Tamron is the far and away winner of our four contestants in resolution at f/2.8 (though the f/4L concedes this by default).  In practical use for most subjects, however, it would be hard to distinguish the images from one lens to the other.  The only exception to this rule is close focus shots at maximum aperture.  The f/2.8 aperture is going to produce more defused backgrounds, but this also represents a fairly marginal use of these types of lenses.  This series of images demonstrates how similar in practice these lenses really are.

If you were unable to tell the difference, here’s the clue:  Canon images are first in the sequence, Tamron images are second.  Most of the Tamron images are at f/2.8 (other than some of the landscape shots), while the similar shots from the Canon are at f/4, of course.  I think you will probably agree that in real world use, you aren’t going to be tell a resolution difference between these lenses.  They are just going to produce great looking, sharp images…period.  If you can’t produce sharp results with either of these lenses, then I’m afraid you can’t blame the glass.  These lenses offer the pinnacle of image quality in wide angle zooms.  The shootout will continue, but between our main competitors you will probably have to call this one a draw.

If you want to read the other sections, take a look here:

Part 1:  Specs, Build, and Objectives

Part 2:  Resolution

Part 3: Angle of View, Distortion, and Bokeh

Part 4:  Flare Resistance, Astraphotography, Handling, and Conclusions

Part 5:  Gallery of Favorite Images from the Review


Gear Used:

Canon EOS 6D DSLR Camera (Body Only)
Tamron SP 15-30mm f/2.8 Di VC USD Lens (Canon EF)
Canon EF 16-35mm f/2.8L II USM Lens
Canon EF 16-35mm f/4L IS USM Lens
Rokinon 14mm f/2.8 ID ED UMC for Canon
Adobe Photoshop Lightroom 5 Software for Mac and Windows (Boxed Version)
Adobe Photoshop Creative Cloud 1-Year Subscription
Alien Skin Exposure 7 (Use code “dustinabbott” to get 10% off)

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