Why is my older macro lens sharp up close but soft at longer distances?
Asked 4/5/2013
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I’m using an older Sigma 50mm f/2.8 macro in Nikon mount on a Canon body, along with a 2x Tamron teleconverter. At 1:1 and other close-up distances it looks very sharp, even with the teleconverter. But when I photograph more distant subjects, including landscape tests, the results are soft and stopping down to f/8 or f/11 doesn’t help much. Did older macro lenses commonly lose sharpness at longer focus distances, or is something else in my setup more likely causing this?
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
13y ago
2 Answers
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That would depend on the individual lens, but to make a general statement: no, direct-mount macro lenses that could focus to infinity were generally sharp throughout their focal range. In particular, a macro lens in the 90-105mm range was usually the sharpest lens in a photographer's kit, regardless of the brand (within limits, of course—there have always been $25 specials of dubious origin, whether on eBay, Amazon, or in the black-and-white ads at the backs of photo magazines).
I qualified that somewhat, since there were lenses produced that either required a focusing bellows or that could only focus at all at relatively close distances. Some of them were adaptations of microscope optics; others were highly corrected for apochromaticity (a near-complete absence of chromatic aberration of any kind) and rectilinearity over a relatively small reproduction range (around 1:4 to 4:1), and while that made them spectacular within their range, it would mean they were less than spectacular outside of it. Such lenses generally couldn't be focused farther away than their far-focus limit without deliberate action on the part of the photographer (using short extension tubes rather than bellows, "freelensing", etc.).
That's not to say that no designs were ever compromised for cost and simplicity. In order to maintain correction across a larger-than-normal focus range, some elements of a lens have to be able to move in relation to other elements, even in a unit focus design. (That is, on a lens where focus is achieved by moving the majority of the lens elements, as a group, further away from the film plane/sensor. Unit focus lenses will get physically longer as you focus closer.) And the corrective elements often need to be aspherical (exotic shapes) or have low- or anomalous-dispersion characteristics (exotic materials, like fluorite or expensive-to-produce and hard-to-work-with optical glasses). If the lens was particularly inexpensive, something had to give somewhere, and if the lens was primarily aimed at macro at a time when owning a 50mm "kit lens" was a given, then it is possible that any compromises made were towards the infinity-focus end of the lens's range.
Originally by user2719. Source · Licensed CC BY-SA 4.0
user2719
13y ago
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Generated from our catalog & community — verify before relying on it.
In general, no: macro lenses that were designed to mount directly on a camera and focus to infinity were usually sharp across their focus range, not just at close distances. Older macro lenses were often among the sharpest lenses people owned.
So the softness at distance is more likely due to your setup than to age alone. A likely cause is incorrect spacing from the mount adapter or teleconverter. If the lens sits too far from the sensor, it acts like an extension tube: close focus improves, but infinity focus is lost or degraded. That matches your symptoms.
Another possibility is that this particular lens was optimized mainly for close-range work, since some older macro designs were more “macro-only” than general-purpose. But that was not true of all older macros.
Given that it is sharp close up and poor at distance, check the adapter/teleconverter combination first and test the lens without the teleconverter if possible.
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AI13y ago
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