Passion. What is it? Where does it come from? What does it need? Where do we find it? Where does it go? Once it goes how do we find it again? How can we continually rediscover passion in our careers? These are the types of questions that are put to me daily as I consult with emerging and seasoned professional photographers and other creative entrepreneurs. In this two-part series for photo.net, I will examine the dynamics of passion as it relates to the unique creative journey each one of us has embarked upon. Read More »
These images represent an extreme flare test since they were taken with the full sun
just in the upper left corner of the frame. They are 25% crops from the center of
the image. They were all shot at f5.6 without a lens hood (though that wouldn't make any
difference anyway with the sun actually in the frame).
The images above show that it's pretty clear here that the Tamron SP AF28-75mm F/2.8 lens
displays a lot less flare than the Canon 28-135 IS at 75mm and f5.6. So Tamron's claims of
lower flare in Di lenses isn't just "adspeak"!
The above shots at 50mm still show the Tamron SP AF28-75/2.8 has lower flare than the
Canon 28-135 and also lower flare than the Canon 50/1.8 prime. I'd have guessed the prime
would have been better, but I would have been wrong!
At 28mm, the Tamron SP AF28-75/2.8 is still superior, though the Canon 28-135 isn't
quite so far behind this time. All in all the Tamron SP AF28-75mm F/2.8 lens has very good flare
resistance.
Chromatic Aberration
It's pretty clear from the above figure that at 28mm the Tamron lens shows
significantly less chromatic aberration than the Canon. The use of LD glass is obviously
working here.
At 50mm both the Canon 50/1.8 prime and Tamron 28-75 show very low levels of chromatic
aberration. The Canon 28-135 zoom still shows a trace, but it's certainly better than it
was at 28mm.
At 75mm both the Tamron 28-75 and Canon 28-135 show very low levels of chromatic
aberration. Both would rate as "good".
Distortion
Distortion was very low at 75 and 50mm. At 28mm some barrel distortion could be seen as
shown below:
The bowing of the lines at the top and bottom of the frame is due to barrel distortion.
The slight slant of the lines is due to me not having the sensor plane exactly parallel to
the target! The distortion isn't severe and is pretty easily corrected digitally, but it
could be of concern to some architectural photographers. A digitally corrected version is
shown below:
Macro
The Tamron SP AF28-75/2.8 XR Di LD Aspherical (IF) Macro can focus down to 0.33m, which
gives a maximum magnification of 1:3.9 at closest focus and 75mm. As I mentioned earlier,
this is really more "close focus" then macro since I don't think it's actually
fully corrected for close focus use in the way that true macro lenses are. Testing bears
out this theory. Below is the full frame shot at maximum magnification:
As you can see, distortion is very low. Looking at sharpness it seems to
peak in the center at about f16 (in contrast to "normal" focus distances where
it peaks between f4 and f8) . Chromatic aberration (which doesn't change as the lens is
stopped down) is also evident as can be seen from the 100% crops below. This obviously
lowers edge sharpness.
So while close focusing is a useful option, the Tamron SP AF28-75/2.8 XR
Di LD Aspherical (IF) Macro isn't a substitute for a true macro lens.
The usefulness of an f2.8 close focus lens is illustrated in the next pair of images:
As you can see, the background is significantly more blurred, and therefore less
distracting, in the shot taken at f2.8. This difference in background blur is maximized
when shooting at 75mm and at close distances.
