When shopping for new lenses it’s often hard to compare the differences between one lens and another online. Even in a store, the difference might not be noticeable unless you get a chance to take both lenses out and play with them.
DxOMark to the rescue! This site is run as a manufacturer independent test site which allows for the comparison on hundreds of lenses side by side with a wide range of parameters. What’s even better than being able to compare raw stats, perfect for tech geeks (an endearing term, mind you)? Being able to compare lenses on different camera models. Let’s take a quick look through the site’s main features. (click to enlarge screenshots)
Besides the advertisements, the first thing to note on the site is the fairly easy layout. At first I was a bit confused (this is normal for me) but then learned to find the lenses I was looking for. You can either browse the 400+ lenses in the section below (slow) or simply search for the lenses you want. I’d suggest choosing the “Lenses Only” option in the Advanced section under Search. It’s important to note the search will show results with the given manufacturer name and focal length, whether it is a zoom or prime. Such as a search for “Canon 85mm” will bring up the primes as well as 18-85mm option, as it should.
Each lens notes the US price and has a Select button for adding it to the comparison. 
Once lenses are selected, the main screen shifts to show the most vital of comparison stats, with the option to sort by what is important to you.
DxOMark offers up their overall score, as many sites will, for a quick yes or no decision. Beyond that, to the left are results for Resolution, Distortion, Vignetting, Transmission and Chromatic Aberration. Even further to the right (beyond the screen shot) are Price, Minimum f-stop, Maximum f-stop, Filter Size and other vital info for the tech geeks in the crowd. It is a full, easy to compare, snapshot of the the lenses you have in mind. Want to dig a little deeper? DxOMark allows that as well.
Click “Compare Measurements” and another screen, similar to the first, organizes the vitals again, but this time with the handy [?] you might have been wanting. The [?] offers a chance to get a quick pop-up describing what the tested parameter means, why it’s important and the meaning of the score. DxOMark has put a lot of effort into providing accurate data and test situations and it shows in their lengthy (sometimes dry) explanations.
All meters are arranged with “Poor” on the left and “Excellent” on the right, so the sliders are all relevant for those not wishing to dive into the numerical info. Beyond the first screen are tabs across the top, the most handy of which is the “Measurements” tab. There is truly a dizzying amount of data available in the next screens. I have limited this test to a request from a student looking to buy one of two prime lenses. Otherwise, with a zoom, the amount of comparisons greatly increases and is a delight for those wanting granular data. For instance, I selected Vignetting and got the below results:
The green and red scale again makes understanding simplified. At f/1.4 you can quickly see both lenses are not at their best, but improve as the f-stop number increases (as is expected). Just above the camera models are “Global map” “Profile” and “Field map” which provide more granular information to help compare at different f-stops and focal lengths (if the lens zooms).
Beyond the lens comparison tool, DxOMark allows for comparing lenses on various camera bodies so hopefully you can get an accurate respresentation of how the lens will work on your specific model. While not all models are available, the most popular ones show up in the drop down list for an individual lens (below).
It is important to note that lenses intended for cropped sensors (APS-C) will only show the appropriate cameras for their test, while lenses that work with full frame and APS-C will show more cameras.
Lastly, paging through the information on a zoom lens, like the popular Canon EF 16-35mm II, provides a wealth of color coded information for learning a lens’s prime use areas, such as this chart showing Vignetting at various focal length and aperture settings.
All in all, I found DxOMark.com a very useful site for data gathering and comparison for lenses. For those looking for camera sensor data (ISO performance between different manufacturers, etc.), it can drill down on those stats as well. While it does not contain every combination available, the wealth of information is a great help when trying to decide between different lens or camera choices. My main gripe about the site is the number and placement of ads. I understand all this information is coming free of charge and income needs to be gathered somehow to keep the site running, but the text ads detract a bit from the site. While handy for sharing, the Tweet and Share buttons only bring up the main page for the lens and not the individual data set I was viewing.
Little things, really, for a site with such an extensive, growing library of useful lens and camera selection data.
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