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Sigma 105 macro lens

This page is an example of using a Sigma 105 macro lens with extension tubes and teleconverters.

Equipment - Sigma 105 f/2.8 macro lens, set of three Kenko extension tubes (12 mm, 20 mm and 36 mm), Tamron SP AF 1.4x teleconverter, Tamron SP AF 2x teleconverter.

Method - For a subject I chose a pebble from my daughters rock collection. The pebble is about 19 mm wide and 22 mm high. I have been informed that this is a "leopard skin jasper". This was set on a small table, indoors next to a window with difuse light. A Canon 20D was mounted on a Gitzo tripod with Acratech ball head. A remote release was attached to the camera and mirror lock up was set on the camera. Exposure was Av mode at f/8. The lens was set at its minimum focus distance and the tripod was moved until a rough focus was attained. The final focus was adjusted manually. The remote release was pressed once to flip up the mirror and after a short pause was pressed a second time to trigger the shutter. The RAW images were processed with Adobe Lightroom using the amount of sharpening that I would usually use for an 8.5 x 11 inch print. The files were then exported as jpg images with a width of 800 pixels for posting with this article and as a full size image that was later cropped to 800 x 600 pixels using PaintShop Pro XI to give a 100% crop view.

Observations - Extension tubes produce a much sharper image than either teleconverter. The 1.4x teleconverter produces a sharper image than the 2x. The combination of three extension tubes and the 1.4x teleconverter is useable, but not critically sharp. The 100% crops obtained by this method are not as sharp as a 100% view of the same file in LighRoom.

Conclusion - My eyes are not as good at manual focus as they used to be. I should repeat this test using bright light and a subject with more well defined fine detail.
Sigma 105 mm macro lens
Sigma 105 mm macro lens		 Sigma 105 mm macro lens (100% crop)
Sigma 105 mm macro lens (100% crop)		 Sigma 105 mm macro lens plus Tamron SP AF 1.4x teleconverter
Sigma 105 mm macro lens plus Tamron SP AF 1.4x teleconverter		 Sigma 105 mm macro lens plus Tamron SP AF 1.4x teleconverter (100% crop)
Sigma 105 mm macro lens plus Tamron SP AF 1.4x teleconverter (100% crop)
Sigma 105 mm macro lens plus Tamron SP AF 2x teleconverter
Sigma 105 mm macro lens plus Tamron SP AF 2x teleconverter		 Sigma 105 mm macro lens plus Tamron SP AF 2x teleconverter (100% crop)
Sigma 105 mm macro lens plus Tamron SP AF 2x teleconverter (100% crop)		 Sigma 105 mm macro lens plus Kenko 12 mm extension tube
Sigma 105 mm macro lens plus Kenko 12 mm extension tube		 Sigma 105 mm macro lens plus Kenko 12 mm extension tube (100% crop)
Sigma 105 mm macro lens plus Kenko 12 mm extension tube (100% crop)
Sigma 105 mm macro lens plus Kenko 20 mm extension tube
Sigma 105 mm macro lens plus Kenko 20 mm extension tube		 Sigma 105 mm macro lens plus Kenko 20 mm extension tube (100% crop)
Sigma 105 mm macro lens plus Kenko 20 mm extension tube (100% crop)		 Sigma 105 mm macro lens plus Kenko 36 mm extension tube
Sigma 105 mm macro lens plus Kenko 36 mm extension tube		 Sigma 105 mm macro lens plus Kenko 36 mm extension tube (100% crop)
Sigma 105 mm macro lens plus Kenko 36 mm extension tube (100% crop)
Sigma 105 mm macro lens plus Kenko 12 and 36 mm extension tubes stacked
Sigma 105 mm macro lens plus Kenko 12 and 36 mm extension tubes stacked		 Sigma 105 mm macro lens plus Kenko 12 and 36 mm extension tubes stacked (100% crop)
Sigma 105 mm macro lens plus Kenko 12 and 36 mm extension tubes stacked (100% crop)		 Sigma 105 mm macro lens plus Kenko 12, 20 and 36 mm extension tubes stacked
Sigma 105 mm macro lens plus Kenko 12, 20 and 36 mm extension tubes stacked		 Sigma 105 mm macro lens plus Kenko 12, 20 and 36 mm extension tubes stacked (100 % crop)
Sigma 105 mm macro lens plus Kenko 12, 20 and 36 mm extension tubes stacked (100 % crop)
Sigma 105 mm macro lens plus Kenko 12, 20 and 36 mm extension tubes stacked plus Tamron SP AF 1x4x teleconverter
Sigma 105 mm macro lens plus Kenko 12, 20 and 36 mm extension tubes stacked plus Tamron SP AF 1x4x teleconverter		 Sigma 105 mm macro lens plus Kenko 12, 20 and 36 mm extension tubes stacked plus Tamron SP AF 1x4x teleconverter (100% crop)
Sigma 105 mm macro lens plus Kenko 12, 20 and 36 mm extension tubes stacked plus Tamron SP AF 1x4x teleconverter (100% crop)

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