Micscape Review: The ExoLens PRO Zeiss system for the smartphone.
Assessment of the Zeiss Vario-Proxar 40-80 T* Macro-Zoom lens.

by David Walker, UK

There are a wide variety of approaches that have been adopted for extending the macro capabilities of smartphone cameras. They can vary from the simple and fun use of a water drop on the lens, using a loupe, through to dedicated add-ons from the cheap to increasingly sophisticated with prices that reflect this. I haven't tried any of them as prefer to use a small 'dumb' phone outdoors and if plan to take macro, carry a compact camera with good facilities such as my current Olympus TG-5. However, I recently stumbled on an add-on macro lens that piqued my interest, it had the magic label Zeiss. Unsurprisingly the lens and others in the range were expensive new but the system has been discontinued so items have depreciated heavily, the macro lens sometimes down to a fifth of the typical current new price where still available. Most of the ExoLens / Zeiss system items are regularly offered on eBay.

Out of curiosity I bought an example to assess and if it had no real role for me could sell on at a similar price. It was also an opportunity to own some sort of Zeiss camera lens. Zeiss make a splendid and very expensive range of lenses for Nikon, Canon and the Sony E-mount. I have a camera body in the latter two mounts that almost use solely on my compound and stereo scope so could not justify the cost of one of their lenses for either.

In this mini-review have adopted a tabular format with short comments. The three types of ExoLens bracket systems are described and the three lenses with brief assessment of the telephoto and more in-depth of the macro lens.

In Use
Phone horizontal focussing down with natural sidelight.

Graph paper is useful for assessing the field of view and any marked chromatic or geometric aberrations. The images below use 2 mm / 10 mm grid paper. The camera was horizontal using a stereo microscope ring mount for focus. Light from a bay window. Diffuser ring left off. Aberration control - chromatic, geometric and planarity of focus quite acceptable for most subjects. The close working distances especially zoomed in blocked available light and requires additional lighting.

Smartphone Apple iPhone 7, rear lens, fixed f1.8 aperture, six element lens.
Halide photo app used which has manual and autofocussing, EV control etc.

All images are out of phone, unmodified, uncropped resized using bicubic sharpening.

The native lens at approx. closest focus. with field of view ca. 10.5 x 8 cm.

Macro lens at longer focus point with field of view ca. 4.5 x 3.5 cm.

Macro lens at shortest focus point with field of view ca. 3.5 x 2.5 cm.
Shading marked so requires oblique light for a desktop macro setup.

Zoom out, with good light can be useful for macro indoors.

Zooming fully in.

Outdoors

Zoom fully out and fully in. Ringlet butterfly. Both 1/155th sec ISO 20. Outdoors the lens and phone blocking the light can be guarded against with phone vertical by choosing a suitable phone position.
Click on each butterfly image to see the master. It maybe a quirk of the sensor or minor camera shake but there are halo images around paler parts of the subject (righthand image) e.g. the white bars on the antennae. At 1:1 because of noise reduction and jpeg compression the detail will not be as fine as for larger sensor systems. Although the Halide app allowed RAW image capture but did not notice much improvement.

Zoom fully out. 1/150th sec ISO 20.

.
1/523 sec ISO 20.

1/463 sec ISO 20.

1/3300 sec ISO 20. Brightened a little post capture.

1/610 sec ISO 20. Rosebay willowherb.

Comments to date

As remarked earlier the macro lens was a speculative purchase now that it is heavily depreciated used but while having some doubts as to its practicality. However, it is finding a role for my photo' work. On most local walks I travel light with no bag so the photographer's mantra that it is the camera being carried that is used applies. With macro lens already fitted, it sits in back trouser pocket and hardly noticed (in a plastic bag so that lens cap is not lost). So any speculative opportunities for macro can be taken.

The Edge Bracket used here does not prevent normal operation of the phone although the ExoLens case would be the more practical. The weight of the macro lens does unbalance the phone somewhat but not unduly. The heavier telephoto lens much more so and have no real use for it. If adding and removing the lens outdoors, care needs to be taken that the lens caps especially the tiny rear one are not mislaid.

Indoor macro work with phone horizontal needs oblique lighting at the closer zoom settings.

I have not compared the lens design and performance with other dedicated lens systems for the smartphone.

Photos can only be as good as the phone camera of course and it does not pay to 'pixel peep' smartphone images as the sensor is tiny and noise reduction often applied. For top quality macro work a bulkier setup would need to be taken out such as my Canon 600D DSLR (APS-c sensor) with appropriate lenses but that is rarely a system I choose to take on casual walks because of the bulk. Less bulky is my Olympus TG5 but despite its super macro features its sensor is tiny and it shows compared with DSLR imagery.

The iPhone 7 like most current models has a fixed aperture lens but the 4 mm fixed focal length is fast at f1.8 so exposures on a bright day have been fast and have been pleasantly surprised at the number of successes of acceptably sharp images despite the perennial problems of subjects moving in a breeze and the rather awkward technique of photography using a phone by holding it some way from body while inspecting the screen.

Comments to the author are welcomed.

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