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The Century +7 achromatic diopter lens is made for the professional HD Video/broadcast market so it feels a lot more solid when you pick it up, 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, Century +4, and +7 are some of the very best tube lenses that I have found.

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

TECHNICAL DETAILS

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

Part Number: 0AD-5870-00

Strength: +7 diopter

Focal length: 142.85mm

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.

In the April 2017 Century price list the +7 is listed but as of today in 2018 the lens is missing from the Schneider Optics website. So I would recommend buying one if you come across one on the used market.

IMAGE QUALITY

A series of images was shot with each lens in 5 micron steps, and the sharpest image was chosen for center, off-center, and corner using Photoshop at 100% actual pixel view. All images were shot as a single RAW files and processed in PS CC with all noise reduction and lens correction turned off, all settings were zeroed out (true zero) and the same settings were used for all of the images. All of the images shown here are single files.

THE EQUIPMENT

Objective: Mitutoyo 5x M Plan APO
Camera: Sony α6300, model ILCE-6300, also known as the A6300
Sensor size: 23.5 × 15.6 mm. APS-C. 28.21 mm diagonal. 3.92 micron sensor pitch
Flash: two Godox TT350s wireless flash units, one Godox X1s 2.4G wireless flash transmitter
Vertical stand: Nikon MM-11 with a Nikon focus block

click on any image to see a larger version in a Lightbox viewer.
Right click, or two-finger press any image, and select Open in a New Tab or New Window to see the full size file.

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Below are 100% crops of the center, off-center and corner areas of the 5x image above.

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THE BOTTOM LINE

The Century Achromatic +7 diopter is sharp, very well made and has great chromatic aberration suppression, so this one gets a highly recommended rating. The lens might be more expensive than lenses like the Raynox or Sigma LSA but the image quality and professional level of construction make the lens a bargain.

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.

For macro photography with a infinity-corrected objective you can use almost any type of telephoto lens, this includes telephoto lenses, zoom lenses, diopter lenses, enlarging lenses, and even large format process lenses. Unfortunately none of these larger lenses like a zoom and telephoto lens will be able to setup as rigidly for studio work as a diopter, like the century, or a tube lens like the Thorlans ITl200. Also the image quality, especially corner performance, with a zoom lens will almost certainly not be at the same level as a lens like the Century or Thorlans ITl200.

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