Review of the Minolta 3x-1x Macro Zoom

October 5th, 2005 - 04:33:50 PM:

Introduction

Did I already mention that I'm a macro nerd? Well, this year I was photographing a lot of very small spiders and insects, and I was always fighting to get the necessary magnification. Even when using high-quality equipment like the Minolta 200/4 APO Macro G, combined with the Minolta APO 1.4× and 2× TCs, magnification often wasn't large enough. After cropping the images to the desired field of view, the loss of quality caused by cropping and by the TCs became quite noticeable. So I started looking for a high quality lens that allows larger than 1× magnifications without using TCs or other accessories. Fortunately Minolta is making such a lens, the 3×-1× Macro Zoom. In fact, Minolta was the first to make such a lens, and they remained the only one for about a decade. It was only recently that Canon joined Minolta by producing their MP-E 65 mm 1-5× Macro.

Finally, a 3×-1× turned up on eBay, and I bought it. Here are my first impressions:

Lens features

AF 3×-1× Macro zoom
  • maximum magnification 1:1 (1×) to 3:1 (3×)
  • maximum geometric aperture f/1.7 to f/2.8
  • working distance 40 mm to 25 mm
  • integrated tripod collar with focus rail
  • 7 aperture blades
  • non-rotating filter threads, 46 mm size
  • motorized magnification setting and rotation
  • full metal construction
  • comes with front cap, rear cap, macro stand and hard case

The 3×-1× Macro Zoom is a very special lens. First of all, the lens is slightly misnamed, as it is not really a zoom lens. The photographer can not change focal length and focus independently. Focal length varies only slightly with magnification between 52 mm (at 1× magnification) and 45 mm (at 3× magnification). This lens really is a fixed focal length lens with a built-in variable extension tube. The only difference between this lens and, for example, the 50/1.7 is the range of extension. Extension is never zero, meaning that the lens can not focus to infinity. With its minimum extension, the lens focuses at 1:1 magnification, and the working distance is 40 mm. Maximum extension results in 3:1 magnification and a working distance of 25 mm.

The maximum geometric aperture of this lens is f/1.7 at 3× magnification and f/2.8 at 1× magnification. The geometric aperture determines mainly depth of field. However, since extension is so long, the maximum effective aperture is much smaller. It's f/6.7 at 3× magnification and f/5.6 at 1× magnification. This effective aperture determines exposure. The camera knows about the effective aperture and displays aperture numbers from 5.6 to 64. You never see the geometric aperture displayed on the camera, only effective aperture. This means that you can use a hand-held exposure meter without a problem. You can set aperture and exposure time as displayed on your external meter, and you will get correct exposure. This is in contrast to other macro lenses, extension tubes or bellows. With these, you have to calculate light loss due to extension manually.

The lens barrel is mounted on a tripod collar with an integrated focus rail. A small knob fixes the focus rail at the current position, and a bigger knob moves the focus rail between −20 mm and +20 mm.

The extension tube is moved by a small motor built into the lens. It does not move fast (about 12 seconds from 1× to 3×), but that's just fine, because it gives you the necessary precision. The same motor is also used to turn the lens between horizontal orientation and turned left by up to 135 degrees. A small switch on top of the lens barrel attaches the motor to either the extension tube or the rotator. You can not move the lens in either dimension manually. The motor is powered by a standard 2CR5 lithium battery, the same type that was used for many Minolta AF camera bodies. Since power is not drawn from the camera, the lens is compatible with even the oldest Minolta AF bodies which do not have motor power supply pins on the lens mount. These appeared only with the xi series bodies, about a year after this lens was released.

The 2CR5 battery is specified to last for 1000 cycles of moving the lens from 1× to 3× magnification and back, and then turning it by 135 degrees 500 times. This means that the battery should last quite long.

There are two principal ways to focus the lens. The first way is to use the focus rail. This keeps magnification constant, but the working distance changes (because the lens moves back and forth). The second way is to use the camera's AF drive, moving the front group of the lens. This keeps working distance unchanged, but slightly changes magnification. There is no way to move the focus group of the lens manually. The magnification scale on the lens indicates the range in which the focus group can move.

The lens has 46 mm filter threads. These are located at the focus group, not on the lens barrel. The outer diameter of a filter should not be much larger than 46 mm, otherwise the filter would hit the lens barrel when the focus group is moved into the lens. So using a filter adapter to fit larger filters on the lens is a no-no!

The lens comes with a macro stand. When you attach the lens to the macro stand, it positions the lens at the right distance to shoot between 1× and 3× magnification. Its three “legs” are spaced to allow the macro ring flash to be mounted at the same time.

The whole assembly comes in a case that not only provides space for the lens and macro stand, but also has prepared cutouts for the 1200 Macro Ring Flash with controller and adapter rings, a camera body, a replacement battery and film cans or other small accessories.

The front cap of the lens does not attach to the filter threads as with other lenses (for reasons explained above), but is lined with a strip of velvet that holds the cap on the lens barrel. While the front cap doesn't immediately fall off the lens, it's quite loose. I can imagine a better design that snaps onto the groove that otherwise holds the ring flash unit.

Using the 3×-1× Macro Zoom

Macro photography is always a technical challenge. The larger the magnification, the more difficult it gets. At 1× and larger magnifications, even very slight movements of the subject will be very visible in the image. Depth of field is paper thin, even when using very small apertures. The small working distance makes it hard to not block all light that falls on the subject. The small effective aperture results in long exposure times in which, again, the subject may move.

The 3×-1× Macro Zoom is definately not a snapshot lens. It requires careful technique, otherwise the results will be just disappointing. Using a tripod is almost a must. At most, you can use it semi-handheld, ie. supporting the lens and using your fingers as a makeshift tripod.

The field of view varies between 36 mm × 24 mm and 12 mm × 8 mm if you're using a film camera, and 23.5 mm × 15.7 mm and 7.8 mm × 5.2 mm if you're using a digital camera with an APS-C size sensor. What you intend to photograph has to fit into this frame. Depth of field is very narrow. At 1× magnification it's at most ± 1.5 mm (at f/54). At 3× magnification it's a tiny ± 0.25 mm.

The greatest challenge is to have enough light for acceptable exposure times. If you're shooting at daylight, you can have the sun neither in your back nor in front of you. In both cases either the lens or the object would block out the sun. Lateral light or diffused light works best with these small working distances. Another option to get some light between object and lens is the Macro Ring Flash 1200 (or its predecessor, the Ring Flash 1200AF-N). The flash tube unit fits onto the 3×-1× Macro Zoom without an adapter ring. Normally when using a ring flash, the strictly frontal lighting gives everything a “deer-in-the-headlights” look. With very short working distances, however, the angle between flash tubes, object and lens is much wider, ie. lighting is less frontal. I expect much more pleasant looking results when using the Ring Flash with the Macro Zoom. I intend to get the Ring Flash soon, and will update this review when I have new results.

The Macro Twin Flash 2400 can not be used with this lens. There is no adapter ring for the flash tube holder to mount it on the lens, and normal filter adapters can not be used (as explained above). Furthermore, the flash tubes don't tilt enough and are too far away from the optical axis to illuminate an object at such short distances.

Sample images

Here are a few sample images:

Conclusion

  • Very solid construction
  • Complete accessories
  • Front cap should have better design
  • Requires careful technique

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© 2005 Michael Hohner