|Ultra-wide Angle Lenses|
IntroductionHere is some analysis of the "MTF (resolution)" data for a number of ultra-wide angle (UWA) lenses from the test reports found on photozone.de. It includes the following lenses:
Key to the data in the charts below:
Preliminaries: Effect of sensor size in these test resultsOne of the interesting factors in these tests is the effect of the resolution of the camera on the results. Ideally I think you would want to test using a camera body whose sensor is not the limiting factor. And do all tests using the same camera body. That's not practical because the camera sensors are continually improving. The folks at photozone specify in their reports which body they tested with and much to their credit, repeated the test for some of these lenses (the Canon 10-22 and Canon 24-105) on several generations of camera bodies (the Canon 350D, 50D, 5DII - with 8, 15, and 21 MP sensors respectively).
This first pair of charts compare an 8MP sensor (350D - the solid lines) with a 15MP sensor (50D - the dotted lines). The chart on the left is at the wide end (10mm), the one on the right is at the long end (22mm). All the data is using the Canon 10-22:
Here is a similar comparison, this time with the Canon 24-105 - and now including a 21MP sensor (5DII). Wide end (24mm) is on the left, long end (105mm) on the right.
Here is another way of looking at the same data. Each thin line is a separate combination of zoom-setting/f-stop setting across the 3 camera bodies. Center and Border of the image is also diferentiated. For example, one line might be the data for [ 24mm, f/4, Center of the image ] across the 3 bodies. The thick red and green lines are the averages for the 24mm and 105mm data sets.
|The results (y-axis) are all relative to the 350D data point. So, the 50D average resolution is 1.24x or 24%
higher than the 350D. And the 5DII average resolution is 1.67x or 67% higher than the 350D.
BTW, the 2 green lines that
rise a little above the rest are
'105mm f/4 Center' and
'105mm f/5.6 Center'.
The number of rows of pixels for each of these sensors are shown to the right.
The 1.63x for the 5DII vs 350D looks to be in line with the 1.67x average increase shown above. The 1.24x increase of the 50D seems a little low though, considering the 1.38x increase in the number of rows of pixels. I assume that's because the 50D sensor is much denser (5.4 MP/cm² compared with 2.4 for the 350D) reducing the 50D individual sensor pixel's light-gathering ability.
Assumming all else being equal (same test procedure, same lens, same post processing of the images, etc), the results are very much dependent on the body and sensor size. Thus compare results between tests that used the same body.
OK, so on to comparing UWA lensesSo for an apples-to-apples comparison (w.r.t. sensor size), here are the results using the available test data for the Canon 50D (a 15MP sensor):
Here are all the results using the available test data for the Canon 350D (an 8MP sensor):
My decision w.r.t. buying an UWA lensAfter mulling it over a while, I bought the Canon 10-22mm f/3.5-4.5 - mainly I think because of what I hope is better piece-by-piece-off-the-production-line quality control and (based on this article) it appearing that the initial design/production bugs having been well worked out by now. Since I retired, I live outside the US and returning a "bad copy" of a lens would be a nuisance (as well as expensive). Here are some photos taken with the lens. And a couple "big sky" photos.
|Do Sensors “Outresolve” Lenses?|