LensTip.com

Focusing

The Laowa 2.8/90 Macro is a manual lens so focusing is purely manual. It is done with a help of a huge and comfortable ring that is as wide as 69 mm. Its part with a smaller diameter you get a clear distance scale expressed in feet and meters along with a mapping scale; the enlarged part features fine but comfortable ribbing. The ring moves evenly, smoothly, and is properly damped; its focus throw amounts to 210 deg, a high value.

It's worth adding that in theory the focusing should be helped by a significant DOF scale put under the ring we've just described. Unfortunately its practical use is very slight – firstly the markings concern the f/5.6 aperture and they are put very close together.

Lack of contacts also doesn't make focusing more comfortable – the camera body doesn't know that you move the focus ring so it cannot use automatic image resize in the viewfinder or in the display

Focus breathing

Focus breathing tests show refraiming images as you oversharp them. We conduct the test by manually passing from the minimum focusing distance to infinity with the aperture stopped down; then we check how the field of view of the lens changed as a result.

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A change of the frame ranging from 0 to 5% we consider to be low. Between 5 and 10% we can speak about a medium level. Usually these are also maximum values compensation algorithms, present in some bodies, can effectively deal with. A high level constitute results between 10 and 15%, more than 15% means a very high level.

The test video of the tested Laowa is presented below:

Based on the recording, shown above, comparing freeze-frames before and after oversharpening we can assess the focus breathing of the tested lens and it roughly amounts to:

• ca. 45% for the 1:2 reproduction ratio,
• ca. 83% for the 1:1 reproduction ratio,
• ca. 160% for the 2:1 reproduction ratio.

These values exceed so much our definitions of 'very high' or even 'monstruous' levels that it would be difficult to find a good description of them in any language and determine the proper level of focus breathing of the Laowa. Still it should be emphasized that criticizing a closed macro construction for focus breathing is like criticizing a human being for breathing and producing carbon dioxide. In both cases breathing is simply necessary to function properly or live. Still, the scale of the problem might be properly assessed by comparing the tested lens to the Tamron 2.8/90 that showed that even a closed macro construction can breathe significantly less.

Of course such high breathing values make also huge changes in effective focal length and effective aperture values. We can't say what big exactly these changes are because here they are not linear. We can only say that the focal length of the lens increases significantly on passing to the macro scale and the aperture becomes distinctly slower. If you wanted to determine it precisely you would have to take a sharp photo of a testing chart at every mapping scale, listed above. Knowing the dimensions of this chart and the distance from the aim you can assess the field of view and then progress to the effective focal length. The problem is that it's very hard to assess well that distance because it should be measured up from the main plane of the lens and it changes and difficult to define – after all you deal here with a closed and changing optical construction.