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08.19.10         photography  

Best Walk Around Lens - Canon 18-200 vs Sigma 18-200 vs Tamron 18-270

This is going to be a long article- will be posting throughout the day (hit refresh to see new additions).

Looking for a very good, “all purpose / general use” lens for your Canon camera? While it is impossible to have a lens that is perfect for every situation, there are a few lenses that can do a lot of things very, very well, and it ultimately depends on what type of photographer you are and what your purpose is with those images. I had the opportunity to compare three very similar type lenses:

Canon EF-S 18-200mm f/3.5-5.6 IS
Sigma 18-200mm f/3.5-6.3 DC OS
Tamron AF 18-270mm f/3.5-6.3 Di II VC LD

They look very similar on the outside, many photographers ask what are the differences between them if any. An important note: each of these lenses were designed for APS-C type sensors, so these are the smaller 1.6x crop sensor camera’s such as the Canon 7D, Digital Rebels, and 10-50D’s, and aren’t made for full frame cameras like the Canon 5Dii.

Something I realized very early on was I had to be careful not to get sucked into a tidal wave of tedious, minutia type differences, and spend months examining these lenses. This is something neither you, nor myself have time for, and as you will see, this is still a very extensive review. Instead of focusing on the actual performance of each lens, I decided to concentrate on how well they stack up against each other. I had a great time figuring out little tests that would help differentiate their performance on a level that every user would understand and appreciate. Therefore, many of the tests, while repeated several times, were also very “quick and dirty”.

Sharpness: Winner: Canon, 2nd Tamron, 3rd- Sigma
I performed a number of “sharpness” tests using a Siemens Star Pattern. I was careful to lock down my Canon 7D in each of these tests, use a timer and compare multiple images. What I originally was looking for was the sharpness of the lines as they approached the center of the star, but there were several cases were it wasn't as easy to see as in others. What made this harder to determine was that the sharpness of each lens seemed to change a little with differing focal lengths and apertures. I quickly noticed though that instead of looking at the star itself (and getting dizzy) the text letters of my iPad were usually quicker to decipher. In many cases, such as this, the Canon and Tamron were very close (again depending on focal length and aperture). At other focal lengths, the Canon looked better, because of this and the fact that this is supposed to be a quick and dirty test- I have to give the edge to Canon. The Sigma lens always seemed to look a little soft upon magnification.

Image Stabilization- Winner: Canon, 2nd Tamron, 3rd- Sigma
Canon claims that it’s image stabilization will make up for 4 stops total difference of shutter speed. I’ve read many tests that have it between 3 and 4, but that wasn’t my question. My question was, which one is best? The test involved again taking a picture of a Siemens Star Pattern from 20 feet away, only this time I was in a sitting position (which would help most eliminate body movement) and I was taking pictures of the pattern handheld, at a shutter speed of 1/15 of a second. The reason I did this is because I know that hand movement, breathing body rocking, all start having a huge effect on your images once you get down to 1/15th of a second. The lens with the best IS system would have the highest number of quality images out of something like 30 test shots.

While I initially looked at the Star Pattern, it was the time on my iPad that made it easy to see. The Canon was the best, the Tamron was a very close second, and the Sigma was so bad, I wondered if the IS was even working, which is a real possibility (it may not have been working at all). I was probably most impressed with how well the Tamron's version of IS worked. Not quite as good as Canon's, but still very good.

Focusing Motor Speed- Winner: Canon, 2nd- Tamron and Sigma Tie

This one was a little tricky to figure out, but I think I got it. Most lenses today are built with tiny little motors inside that move the lens elements under the direction of the camera’s focusing system. While typically these focusing intervals happen very quickly (within a second), in most normal circumstances it would be very hard to tell a difference at all.For most hobby type photographers, this probably wont matter. For someone shooting sports, it absolutely will. The faster the lens motors work to track a moving subject, the better the images.

To test this, I decided to find 2 dimly lit objects in a poorly lit environment, which were very far apart. This would require the lens to move the lenses elements as far as possible. I turned on my focus lock beep indicator (which is a loud sound you can hear), and focused back and forth between my 2 targets for 50 “focus locks”indicated by the beep. By repeating these little differences in motor speed several times, the lens with the fastest motors would be able to complete the cycle before the other 2. I timed the test by initially taking an image of a stop clock and ended the test by taking another picture of the same stop clock. While it may not have been perfectly precise, the Canon lens was far and above superior to the Sigma and Tamron when it comes to lens focus motor speed. The Sigma and Tamron performed about the same. What these means is if you are shooting fast moving subjects, such as sports the Canon is going to be your best bet of the three.

Wide Angle Lens Distortion- Winner: Sigma, 2nd- Canon, 3rd- Tamron

Because we are dealing with lenses with a very dynamic focal length range, I was interested in what the differences in distortion were at the maximum focal lengths (18mm) because this is typically where we see the greatest amount of distortion. To measure this, I took pictures of a metal grate from directly above. The grate essentially provided a line grid that would allow me to look for “bends” associated with wide angle lens distortion, you can see it particularly in the corners as “pinching”

While the Sigma in this particular test won, I should also point out it ran into some issues when considering other types of distortion such as CA, as well as focus distortion (where the center may be in focus and the periphery may or may not depending on focal length. While it is just too much to go into, the Sigma performed better than expected. Overall I believe the Canon was better when considering all types of distortion, at all focal lengths and apertures. I also concede I may have gotten a bad Sigma lens, and I am willing to reconsider otherwise.

Chromatic Abberation Distortion: Winner Canon, 2nd- Sigma 3rd- Tamron
Chromatic Abberation is an optical problem that occurs when a lens is unable to focus all the wavelengths of light properly, which results in fine colored haze around edges in your images. (Read more on Chromatic Abberation Here). Higher quality lenses typically have less CA, with cheaper lenses resulting in greater artifacts. A good way to test your lens for CA is to take a picture of something thin and dark on a very bright background, and compose it on the outside of the frame, as with these antennas. I am particularly interested in the last one. Also, while it is hard to see, look on the opposite side of the image, where the edge of the building ends- can you see it?
My main test involved looking on both sides of the 3rd antenna (furthest to right), the left side shows a yellow haze, while the right favors purple. When it comes to Chromatic Abberation, it appears that the Canon has the edge. While it may initially appear that the Sigma is better, compare the yellow sides, and another problem with the Sigma was the actual sharpness of the antenna itself- I repeated this shot many times, and could not get it any sharper than this- a hint of some of the sharpness issues with the Sigma. Last was the Tamron, which appeared to have the worst artifacts for CA. I tend to give the Tamron some lee-way though because of its amazing focal length range (a world record at over 15x (from 18-270mm), quite astonishing to be honest. All three images here were shot at 200mm.

Sports Test Shots-
I ran over to the local high school with the permission of their coach to get some sports shots on AI Servo mode. For the most part all lenses did great but as expected, I was very happy with Canon’s images taking into consideration sharpness, IS and motor speed. It seemed more of the fast moving subject type shots were more in focus. The Tamron did very well, and even the Sigma did great. Here are samples of all three lenses with fast moving subjects involved. For the most part the Shutter Speed was 1/2000, but there were tweaks and adjustments to while shooting which can explain some of the exposure differences you are seeing, in any event you get the idea.
I liked the ability of the Tamron to get in closer. How much difference does that extra 70mm make on an actual shot with the Tamron? Here it is. First shot taken at 200mm, the image below at 270mm. The red box in the first indicates the approximate fit of zooming in.

Portrait Shots-

Unless you are using a magnifying glass, you wont have many issues with shooting portraits with any of these lenses, just don't expect the nice buttery backgrounds associated with very wide apertures. The above shot was taken by all three lenses at 35mm on a Canon 7D (~56mm) which is a perfect length for portraits (Shots were f4.5, 1/160, 400 ISO). Note that while the model is different sizes, it is possible I wasn't standing in the exact same spot. I also noticed that the Sigma is a little softer, as it was in other test shots, but the idea of this comparison is that when it comes down to it, they all do great for portraits, at least on the "normal person scale".
Wild Card Features- Winner Tamron

While many will contest the extra 70mm focal length range is a gimmic, in my opinion, it isnt. True, there is more distortion at these extreme focal lengths, again not enough to really notice for most non-pros. Nearly all of the images I took in Haiti, including of Evan Monsignac were taken with the Tamron lens. (This is the exception of the main iPhone shot I took when he first came in). Those images were found on literally hundreds of websites and newspapers worldwide. When I first heard of it, I was skeptical because of the Tamron name. Do not be fooled, it is a very capable lens.

The 6 Year Tamron Warranty however is the real kicker. This needs to be taken into serious consideration when buying your walk-around lens. Granted, there are times I will reach for the Canon 18-200 over the Tamron, but I think most general purpose lens seekers are going to love it for the warranty. Sigma and Canon both fall short with their 1 year warranty. In this aspect, you are getting 6 times more commitment from Tamron as a gesture of good faith you can trust their equipment. The Tamron lens is the one I most often use when going on a long trip and so far I couldn't be happier with it.

Overall Winners And Suggestions:
Surprisingly, each of these lenses has a place in different photographers camera bags, and it really depends on what your needs are:

Why you would want the Sigma 18-200:

Price. It’s by far the most affordable. While in the head to head comparison the Sigma fell short, it is an absolutely wonderful lens. Surprisingly, even after all these tests, I do not think most normal people would even be able to tell when inspecting images from each lens. It was only in very extreme conditions and circumstances that it’s flaws were noticeable. Priced at just $369 at Bhphoto.com, it is an absolutely fantastic deal, especially if you plan on banging your lens around for a few weeks. The photographers who will want this are the one’s on a tight budget, or are perhaps casual shooters, non-pros who want a great all round lens.

Why you would want the Canon 18-200:

Quality. The Canon consistently outperformed the other two lenses. It was sharper, the IS was significantly better, motor speed, sharpness, distortion, etc were all very good. If a Canon “L” lens is a grade A, this is probably a “B- to B” lens. Not outstanding, but still extremely good quality for it’s size. Loaded with features, also one of the more expensive. It just goes to show, sometimes you really do get what you pay for.

Why you would want the Tamron 18-270:

Warranty and Extra Reach – Unlike the Canon and Sigma 1 year warranty, Tamron’s comes with a jaw dropping 6 year warranty. Between that and the extra 70 mm (which is another 114mm on a 1.6 crop factor sensor body) that puts its range between 28mm-432mm, which is pretty much ridiculous when it comes to lens range. That said, I did notice some of the distortion issues became more apparent over the 200mm range, but absolutely yes, nature, wildlife and sports photographers are going to appreciate that extra reach. That said, the warranty is what makes this lens so attractive. If it breaks or fails from manufacturing defects within 6 years, Tamron will repair or replace at their expense. There is also currently a rebate on the Tamron that has it priced for ~$519! (that's a steal of a deal!)

Comments or questions? Please let me know what you think in the comments below!

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