My Sigma 250mm f/5.0 Macro

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.

100%, processed, crop from the photo above

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.

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 [url=http://www.fotografainerba.com/] Daniela[/url] 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.

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