LensTip.com

Lens review

Tamron 28-75 mm f/2.8 Di III RXD

26 August 2019
Maciej Lata││o

7. Coma, astigmatism and bokeh

Weaker performance on the edge of the frame, observed in the resolution chapter, might be partially explained when you see how the optics of the Tamron 28-75 mm corrects coma. Not often a full frame lens shows distinct coma in the corners of the APS-C sensor and here that aberration can't be noticed only at 28 mm. In the middle of the focal range it becomes noticeable and at 75 mm its level is already distinct. The corner of full frame shows the coma in all its glory but here it reaches the highest level at the 50 mm focal length.

Center, 28ámm, f/2.8 Corner APS-C, 28ámm, f/2.8 Corner FF, 28ámm, f/2.8
Tamron 28-75 mm f/2.8 Di III RXD - Coma, astigmatism and bokeh Tamron 28-75 mm f/2.8 Di III RXD - Coma, astigmatism and bokeh Tamron 28-75 mm f/2.8 Di III RXD - Coma, astigmatism and bokeh
Center, 50ámm, f/2.8 Corner APS-C, 50ámm, f/2.8 Corner FF, 50ámm, f/2.8
Tamron 28-75 mm f/2.8 Di III RXD - Coma, astigmatism and bokeh Tamron 28-75 mm f/2.8 Di III RXD - Coma, astigmatism and bokeh Tamron 28-75 mm f/2.8 Di III RXD - Coma, astigmatism and bokeh
Center, 75ámm, f/2.8 Corner APS-C, 75ámm, f/2.8 Corner FF, 75ámm, f/2.8
Tamron 28-75 mm f/2.8 Di III RXD - Coma, astigmatism and bokeh Tamron 28-75 mm f/2.8 Di III RXD - Coma, astigmatism and bokeh Tamron 28-75 mm f/2.8 Di III RXD - Coma, astigmatism and bokeh


Astigmatism, understood as an average difference between vertical and horizontal MTF50 values, amounted to 6.9% and its level can be described as slight. It's also worth adding that the 75 mm focal length contributed the most to that average value as in its case astigmatism was noticeably higher than in the 28-50 mm range.

- - - - - - - - - - - - - - - - - advertisement - - - - - - - - - - - - - - - - -

- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

One glance at defocused circles of light and you know that there are apherical elements present in the construction. Most probably they are responsible for noticeable onion ring bokeh. You can also have some reservations concerning distinct mechanical vignetting – you can't get rid of it completely even on stopping down the aperture to f/5.6.

Center, 75ámm, f/2.8 Corner APS-C, 75ámm, f/2.8 Corner FF, 75ámm, f/2.8
Tamron 28-75 mm f/2.8 Di III RXD - Coma, astigmatism and bokeh Tamron 28-75 mm f/2.8 Di III RXD - Coma, astigmatism and bokeh Tamron 28-75 mm f/2.8 Di III RXD - Coma, astigmatism and bokeh
Center, 75ámm, f/4.0 Corner APS-C, 75ámm, f/4.0 Corner FF, 75ámm, f/4.0
Tamron 28-75 mm f/2.8 Di III RXD - Coma, astigmatism and bokeh Tamron 28-75 mm f/2.8 Di III RXD - Coma, astigmatism and bokeh Tamron 28-75 mm f/2.8 Di III RXD - Coma, astigmatism and bokeh
Center, 75ámm, f/5.6 Corner APS-C, 75ámm, f/5.6 Corner FF, 75ámm, f/5.6
Tamron 28-75 mm f/2.8 Di III RXD - Coma, astigmatism and bokeh Tamron 28-75 mm f/2.8 Di III RXD - Coma, astigmatism and bokeh Tamron 28-75 mm f/2.8 Di III RXD - Coma, astigmatism and bokeh