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My
Sigma 250mm f/5.0 Macro (April 26, 2007)
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| Canon
EOS 20D, Sigma 180mm f/3.5 EX APO Macro HSM, Sigma 1.4x
TC, 1/40 f/8, iso 400, tripod. Monghidoro, Italy. |
I am a fan of long lens in macro
photography and so far the Sigma 180mm f/3.5 Macro EX HSM has been
my preferred macro lens: it is as good as the Canon, but it cost an
half. But even with such lens, I've always dreamed a longer macro
lens, until I realized that a 250mm macro is a reality: I just have
to mount the Sigma 1.4x TC on the lens, to get a fantastic 252mm
f/5.0, with longer working distance, better background blur and the
possibility to reach the reproduction ratio of 1.4:1!
Even though I use very often the
teleconverters with my 600 f/4, so far I hadn't thought about the
improvement of background - since I use the 600 f4 almost always
wide open, there is not background improvement with TCs: the
background blur is the same both with a 600mm at f/4 or a 840mm
f/5.6. In macro photography, instead, I often use small apertures,
as f/8 or f/11: at the same aperture, a 250mm gives a more out of
focus background than a 180mm, so the 1.4x TC gives a real advantage
in term of separation between the subject and the background.
A more obvious advantage is the longer
working distance: at 1:1, the 180mm has a working distance of 46
centimeters, while the 180 + 1.4x has a working distance of 54
centimeters. If you have to photograph shy subject, the added reach
is a nice plus. Moreover, you can still focus up to 46cm, to go
beyond the 1:1 ratio. At the minimum focusing distance, the Sigma
180 + TC gives an effective RR of 1.4:1, with good image quality up
to f/11 (at smaller apertures, you lose a lot of sharpness and
contrast due to diffraction).
| All teleconverters have some cons
on brightness, autofocus and image quality, but the results
depends by the lens. Of course, there is the unavoidable loss
of 1 stop of light, with the 1.4x, so the widest aperture
becomes f/5.0. This is not a problem for me, since in macro
photography it is necessary to use small apertures to get a
good depth of field, and I almost never use this lens wide
open: the majority of my macro photos had been taken with
apertures between f/8 and f/16. The autofocus can still be
used from 1.2 meters to infinity, but it becomes so slow that
in practice it is unusable: not a problem, since I always use
manual focus in macro photography. What about image quality?
While I don't care about aperture and AF in a macro lens, I
want very high image quality: I'm glad to say that the 180mm
is excellent even with the 1.4x. The sharpness is acceptable
even wide open, and it becomes very good from f/8 to f/16.
There is a little of chromatic aberration, but you can
eliminate it when you convert the RAW file with Adobe Camera
RAW.
In conclusion, I am really happy with my "Sigma 250mm
Macro" - it gives great results, and I've spent just $ 190
to transform my 180 into a 250 (the price of the Sigma 1.4x TC
- I already have the Canon TCs, but they can not be used on
the Sigma 180 Macro lens). Now, I plan to leave the TC mounted
on the lens all the time - there are a lot of advantages, and
none real cons. |
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| 100%, processed,
crop from the photo above |
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Few days ago, I tried for the first
time the 180 with my brand new Sigma 1.4x TC. I was wondering in the
woods with my friend Daniela
when I sad hundreds of these small pink flowers. I spent some time
until I've found the perfect specimen: I wanted to isolate a single
flower against a nice green background. I mounted the lens on my
Manfrotto 190 MF4 - the tripod that I use for all my macro photos,
very small and light, that allows to photograph even from super low
angles. I positioned the lens until I was as parallel as
possible with the flowers, to optimize the depth of field, and I
carefully framed the photo with the Canon Angle-Finder C. This is an
useful accessory that allows to view the image from a more
comfortable position, when you photograph from awkward angles (as I
often do in macro photography ;-)). Moreover, the Angle-Finder
allows to magnify the center portion of the image up to 2.5x, for a
very precise manual focus.
I've taken many photos of the same
composition with slightly different apertures: it is difficult to
judge precisely the depth of field in the viewfinder, so when it is
possible I prefer to take various photos and to select the best one
on my Eizo 19" LCD screen. Since the shutter speed were quite
slow, I used mirror lock up and remote release. To get a real
advantage from mirror lock up, you have to use either the self timer
of the remote; when you use the remote, at the fist click the mirror
turns up, then you have to wait few seconds, and finally you have to
press again the remote release to take the shot.
Do you have
comments or questions?
If you have comments or questions about this
article, feel free to ask in the Juza
Nature Photography Discussion Forum!
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