Tamron SP 24-70 mm f/2.8 Di VC USD
7. Coma, astigmatism and bokeh
The astigmatism is corrected well. The average difference between vertical and horizontal MTF50 values amounted to 4.3%. It is worth noticing, though, that at 24 mm the results were below the average and at 45 mm – above it. At that latter focal length the achievements of the lens are the weakest and it must be said that the astigmatism contributes to it although it is hardly the most dominant factor.
Please Support UsIf you enjoy our reviews and articles, and you want us to continue our work please, support our website by donating through PayPal. The funds are going to be used for paying our editorial team, renting servers, and equipping our testing studio; only that way we will be able to continue providing you interesting content for free. |
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
Let’s check what information defocused images the tested lens can provide.
Very sharp and distinct concentric rings in all defocused images are a real surprise. On stopping down their intensity seems to increase – that change, along with the change of their structure is especially pronounced while passing from f/4.0 to f/5.6. It is exactly that place where the spherical aberration made itself felt the most keenly, all of it confirming our observations from chapter 5. Fortunately there are a lot of that concentric rings with a changeable light intensity and they are densely packed so the blurs in real life photos won’t necessarily look bad. With such a strong background blur and not exactly point-like sources of light those defocus light rings might actually seem to be quite smooth.
