Sigma Life-size Attachment lens
Originally the Sigma Life-size Attachment lens was supplied with the Sigma 90mm f2.8 macro lens as a supplementary add-on close-up lens. When added the maximum magnification ratio went from 0.5x or half life-size down to 1x or life-size magnification. Over the last few years the Sigma LSA lens has become a popular tube lens for infinity-corrected microscope objective photography. The main reason is has become popular is price, it costs about $20-30 USD on the used market, but thanks to Sigma's use of a UD glass, the image quality better than average. The Sigma LSA is going to be just about impossible to beat from a performance vs dollar standpoint, but for more pristine image quality with infinity-corrected microscope objective there are better lenses on the market such as the Thorlabs ITL200 tube lens (which is actually made by Nikon for APO and Fluor lenses).
Sigma Life-size Attachment lens with Sigma MF 90mm f/2.8 macro and AF 90mm f/2.8 macro lens.
You can find the Sigma Life-size Attachment lens with the two lenses above, the Sigma Macro MF 90mm f/2.8 lens on the left and the Sigma Macro AF 90mm f/2.8 lens on the right. Expect to pay less than $100 for the 90mm lens including the Life-size Attachment lens
WHAT YOU NEED TO KNOW
Sigma Life-size Attachment lens Pros
-Low price
-Very good fit and finish
-Easy to install with both M52 x 0.75 external and internal threads
-Good image quality
Sigma Life-size Attachment lens Cons
-The lens needs to set up properly for best results
Whats a Tube Lens Anyway?
The term tube lens comes from microscopy and has become a standardized term for an infinity-corrected tube lens designed for use with a infinity-corrected objective to create a certain effective magnification ratio. An objective lens creates an image of an object at infinity and a tube lens is designed to refocus the collimated light rays into an image on the sensor. Changing the focal length of the tube lens will also change the effective magnification ratio. Microscope objectives are designed to provide the magnification engraved on the housing when they are used with a tube lens of a specific focal length. Microscope manufacturers design their systems with one of several standard tube lens focal lengths, 250mm for Qioptiq, 200mm for Mitutoyo, Thorlabs, Nikon, and Leica microscopes, 180 mm for Olympus microscopes, and 165mm for Zeiss microscope objectives.
Simple Infinity corrected microscope objective and tube lens photography set-up.
How to set up the Sigma LSA lens for macro photography
Thanks to the standard M52 mounting threads the Sigma LSA is easy to set up for a infinity-corrected studio photography set-up. A detailed M52mm setup using the Sigma LSA is available on Closeuphotography.com: https://www.closeuphotography.com/52mm-setup
Set-up for best results:
- 145 mm sensor to lens distance, not infinity focus
- Reverse mount
- 75mm between tube lens and objective
- Images made with the Sigma LSA at infinity focus will have more chromatic aberrations
- Short focus produces a sharper image than infinity focus.
- Normal mounting this lens introduces more chromatic aberrations.
- Short focus, or using a lens with less extension than is needed for infinity focus means that it is "focused" beyond infinity. This would create an unusable blurry image, but in many cases this happens to work well with tube lenses - as described here. Short focus results in shorter "effective focal length" used here for magnification calculation purposes, so for example the Sigma LSA with short focus comes in a 183mm effective FL, this would give you 0.91 x the Mitutoyo objectives marked magnification, for the Mitutoyo 5x M Plan lens this would be 4.58x.
Full image with crop areas highlighted in blue
TECHNICAL DETAILS
Sigma Life-size Attachment lens
Sigma Life Size Attachment Lens
Type: Supplementary add-on close-up lens for the Sigma 90mm f/2.8 macro lens.
Now more commongly used as a tube lens for infinity corrected microscope objective photography.
Strength: +5 diopter
Focal length: 200mm
Optical Design: 2 elements, one UD or ultra-low dispersion type glass
Chromatic Aberration Control: Excellent when setup properly.
Lens mount: M52 x 0.75
Filter threads: M52 x 0.75
Date originally sold: Late 1980s for the Sigma MF 90mm f/2.8 and early 1990s for the AF 90mm f2.8 macro lens.
Cost: This lens is almost impossible to beat for performance vs price. They are pretty easy to find on Ebay and expect to pay about $25 to $45. If there are none online when you check, just set up an alert on Ebay and wait, they will turn up eventually. Sometimes you can find a good package deal with the Sigma 90mm and life-size attachment together for less than $100, in December 2017 I picked up a mint condition 90mm lens with the life-size attachment lens for only $77 including shipping. Some samples of this lens may have slight haze, so I would recommend buying from a seller that offers returns just in case.
Sigma Life-size Attachment lens with Sigma MF 90mm f/2.8 macro lens.
How Does Sigma LSA compare to other tube lenses?
A detailed review and comparison of tube lenses is available here on Closeuphotography.com:
https://www.closeuphotography.com/tube-lens-test
Not all Sigma diopter Lenses Are recommended
There are quite a few different Sigma diopter lenses available on the used market, some of these are single element lenses that are pretty poor compared to the LSA, while others were measured with a focal length of 629mm! Below is a list of lenses that I have tried that are not recommended for use as a tube lens.
Sigma Close-up AML lens
Sigma Lens Accessory Close-up lens
Sigma Optical close-up Lens
Sigma AML-2 Close-Up Lens
Sigma AML72-01 Close-Up Lens
Sigma Achromatic Macro Lens
MORE INFORMATION ON OTHER TUBE LENSES
A test of the Thorlabs ITL200 tube lens is available here on Closeuphotography.com:
https://www.closeuphotography.com/thorlabs-itl200/
Raynox tube lenses:
https://www.closeuphotography.com/raynox-tube-lens/
The Century +4 tube lens:
https://www.closeuphotography.com/century-precision-optics-achromatic-diopter/
The Nikon MXA20696 tube lens:
https://www.closeuphotography.com/nikon-mxa20696-tube-lens-test/
The Mitutoyo MT-1 tube lens: