Century Optics +4 achromatic diopter lens

The Century +4 achromatic diopter lens is made for the professional HD Video/broadcast market and it feels like it when you pick it up, its solid, it feels like a solid hunk of aluminum. The image quality is what you would expect from a lens made for the professional market and at this price level, excellent, in fact, this lens has some of the best image quality I have seen when used as a tube lens with an infinity corrected microscope objective for photography. After buying more than a dozen diopters over the years and testing them, the Century is one of the very best I have seen. In fact its the only tube lens that I have ever tried can offer image quality as clean as the Sigma LSA lens (link:https://www.closeuphotography.com/sigma-life-size-attachment)

WHAT YOU NEED TO KNOW

Century Achromat Pros

-Excellent lateral chromatic aberration control
-Professional level fit and finish
-Easy to install with industry standard threads

Century Achromat Cons

-58mm is the only attachment size available

Whats a Tube Lens Anyway?

The term tube lens comes from microscopy and has become a standardized term for a 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.

For macro photography a tube lens refers to a any lens used for this purpose, including telephoto lenses, zoom lenses, diopter lenses, enlarging lenses, and even large format process lenses. Unfortunately none of these alternative type lenses are specifically designed to work well in conjunction with a microscope objective so most will degrade to a certain degree, some significantly if there is too much separation between the tube lens and the objective. The most common issues are vignetting, and chromatic aberration, especially in the corners.

Why not just use a 28-300 Zoom Lens?

Almost any lens of the proper focal length can work to create an image as a tube lens but there are a few issues with lenses like a zoom. The first is corner performance, a zoom lens will almost certainly cause vignetting and chromatic aberration in the corners. The second is rigidity, a zoom lens will work fine handholding but on a studio set-up with an objective hanging off the end the zoom, there will be too much play and flex which will create issues for macro photography.

TECHNICAL DETAILS

Type: Professional market Video/HDV/DV macro diopter lens

Strength: +4 diopter

Tested Strength: +4.39 diopter

Focal length: 250mm

Tested Focal length: 228mm

Optical Design: 2 elements, one UD or ultra-low dispersion type glass

Chromatic Aberration Control: Excellent

Normal or reverse mounting: For best image quality this lens should be mounted normally.

Lens mount: M58 x 0.75

Filter threads: M58 x 0.75

Cost: Century 58mm Achromatic diopters are available from any large camera shop for about $270-300 USD. These are available on the used market, the two that I own were purchased on Ebay in later early 2018, as new old-stock, unused and in-the-box, for $99-125. USD.

Recommendations

The Century Achromatic +4 diopter is sharp, very well made and has great chromatic aberration suppression, so this one gets a highly recommended rating.

For two years I have been searching for a +4 (250mm) lens to use as a tube lens with a infinity corrected microscope objective. The problem is that very lens I have tried has had chromatic aberrations in the corners. After testing than a dozen lenses, I found the Century +4 achromat, and finally, something with clean sharp corners and no CAs! This lens is the only one I have seen has image quality in the same class as the Sigma LSA.

About Century Optics

Century Precision Optics is an American optical manufacturing firm that has been around since the 1970s and is based in North Hollywood. In 2000, Century was acquired by Schneider Optics, the US subsidiary of Schneider-Kreuznach, the German optical company and makers of photographic and industrial lenses.

The Century +4 Achromatic diopter on Schneider's site:

https://www.schneideroptics.com/ecommerce/CatalogItemDetail.aspx?CID=1081&IID=896

Other Recommended Tube Lenses

if you are looking for a tube lens with a slightly shorter focal length than the Century +4, I recommended the Sigma LSA, a +5, 200mm tube lens, follow this link for more info : https://www.closeuphotography.com/sigma-life-size-attachment