The Amazing "Sigma 500mm Macro" (July 07, 2007)

There are truly few lenses that gives good results with stacked teleconverters. Even the $8,000 Canon 600 f/4 L IS USM gives poor image quality with stacked TCs - I've tried many times, but I've never been satisfied by the results. Until now, the only lens that I've tried with good results with 2x + 1.4x was the Canon 300 2.8 IS, that gives a good 840mm f/8 with quite good image quality (if you stop down at least one stop). I didn't expect to get acceptable results with the Sigma 180, and I've been truly amazed by the results: this lens, coupled with both Sigma 1.4x and Sigma 2.0x, delives a surprisingly good image quality....it is so good that after some post-processing it would be difficult to tell if a photo has been taken with the bare 180 or with 180 + 1.4x + 2x!

I was walking near the Trebbia river when I noticed this nice butterfly. It was 6 a.m. - the great majority of my macro photos is taken in very early morning - and it would have been quite easy to approach the butterfly, but today I had chose to photograph exclusively with the Sigma 180 + 2x + 1.4x, to understand the capabilities and the weakness of this combo. I carefully placed the camera as parallel as possible to the butterfly - even at f/22, the depth of field is quite shallow, and it is important to stay parallel with the subject. The working distance is awesome! This is a small butterfly, it was nearly 2.5 centimeters long, and I've been able to take a frame-filling photo from nearly one meter of distance! If you want to photograph shy subjects, the huge working distance given by the 504mm focal length is a great plus. Focussing is extremly difficult. The widest aperture of the lens becomes f/10 and, as you can imagine, the small viewfinder of the Canon 20D becomes very dark. With the Canon Angle-Finder C the view is even darker, but the 2.5x magnification helps a lot to focus correctly. To be 100% sure of the focus, I often take a test shot and I check the sharpness with the 10x zoom feature of the camera - while it is impossible to judge accurately the focus in the LCD screen of the camera, you can determine if the photo is in focus or if it is out of focus or blurred.

A 100% crop from the processed photo. Click to view a wider crop.

To get the best image quality from the 180 + stacked TCs, I recommend to stop down to f/16 or f/22, as I did in these photos. Of course at f/22 there is some loss of sharpness and contrast due to diffraction, but the image quality is pretty good after post processing, and the background blur is fantastic, thanks to the 500 focal length.

Remember than the camera "see" only the teleconverter attached to the lens, so it reports an incorrect focal length and aperture: it considers the lens a 360mm f/7.1, even tough actually it is a 504mm f/10. The real aperture is one stop smaller than reported - for example, if you set the aperture on f/11, you are actually at f/16; if you set the aperture on f/16 you are at f/22, and so on.

I've taken some photos of the entire butterfly, then I begun to get closer. With teleconverters, the minimum focussing distance remains unchaged, but the magnification is increased - at 46 centimeters, I've been able to take a portrait of this small butterfly!

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!