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I remember that a number of older (80s to maybe mid 90s) zooms had a "macro" mode where you would throw a switch that allowed the lens to focus closer. What was that? was it just a built in extension tube or something more complicated?

Here's a quote describing the Tokina 28-85/3.5-4.5:

"I have recently discovered that there are two versions of the Tokina. I have the earlier one. The earlier one has a narrower zoom ring than the later one. With the earlier one, you enter macro mode by pressing a button and turning the zoom ring past 85."

Source page is http://lists.tako.de/Olympus-OM/2003-11/msg01595.html

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I used to have a Nikon 28-105mm lens with macro capability and a switch for it. The switch could be moved only when the zoom was in the 50-105mm range. When in that range and switched, the lens focus ring could turn further into a designated macro focus range.

So simply, within that 50-105mm focal range some of the lens's groups of elements have moved far enough apart that there's now more room to shift other groups of elements to be able to focus closer. The switch/lock prevents all of those groups from bumping into each other.

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I managed to dig up the answer, at least for Vivitar's 70-210: "But in macro mode, three groups of elements move as a unit to shift the lens's optical center further from the film plane" From

http://books.google.com/books?id=jdUDAAAAMBAJ&pg=PA184&lpg=PA184&dq=how+did+vivitar+series+1+macro+mode+70-210+work&source=bl&ots=0So3sP95D_&sig=H76yOlxj3Dd_0Ry-S1CcGkyTbzo&hl=en&sa=X&ei=ulwZVP-tO9eQNq6Agmg&ved=0CC4Q6AEwAg#v=onepage&q=how%20did%20vivitar%20series%201%20macro%20mode%2070-210%20work&f=false

  • I assume internal focusing removes the need to do this sort of thing. – JenSCDC Sep 17 '14 at 10:12
  • The Sony RX1 has the same thing, you can twist a ring which physically extends the lens barrel for macro mode. – Hampus Nilsson Sep 17 '14 at 11:35
  • @AndyBlankertz Internal focusing may help in some design scenarios. But the main purpose of the macro switch on older lenses was to prevent trying to focus a zoom lens at points where two different groups would need to occupy the same space. – Michael C Sep 18 '14 at 2:39
  • I didn't know that- I thought it was for faster AF, like with primes. – JenSCDC Sep 18 '14 at 15:02
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Modern lenses also have this, usually zooms in the 70 - 300mm range that have a pseudo-macro (say, 1:2) function. The switch stops the autofocus 'hunting' throughout the entire focus range.

Say you're photographing birds in a forest with the focal length at 280mm. They are 30 yards away. The trees are making the AF work a little. Rather than the AF trying to focus from 1.5 yards (ie macro territory) all the way to infinity, the switch limits the focus range to, say, 5 yards, so it doesn't have to hunt as long to find focus.

  • No, as I remember it the switch actually physically changed the lens. – JenSCDC Sep 17 '14 at 8:13
  • Physically changed it how? What did it do after the switch was thrown that it didn't before, physically speaking? – ElendilTheTall Sep 17 '14 at 8:30
  • The Sigma 70-300 DG Macro APO is a good example. Some people thing that the optical formula changes when the macro switch is used, but, as ElendilTheTall says, it just limits the focus range. In the case, of the Sigma 70-300 lens, the slrgear review of it, says that the quality is the same with or without the macro mode, suggesting that the optical formula is exactly the same. – Super Coco Sep 17 '14 at 8:59
  • Furthermore, it would be technically very difficult to add or remove a lens element from the light path with just a very small switch. – Super Coco Sep 17 '14 at 9:06
  • I just edited my question to add an example of such a lens. – JenSCDC Sep 17 '14 at 9:31
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It wasn't a "switch", it was a mechanical latch that allowed you to use a different helicoid path for focus. So yes, it was essentially a built-in adjustable extension tube, but it could only be accessed when the lens was in a limited range of configurations. Often it was just one configuration; on some lenses, it was engaged beyond the long end of the zoom range, on some it was at the short end (which could give you more magnification, but at the expense of working distance). As Dan Wolfgang noted, on some lenses there was still some amount of zoom available, but that was the exception rather than the rule since the usual method was to use the zoom ring as the macro helicoid adjustment (leaving the focus ring for little more than fine-tuning).

  • Well, according to the description of the Vivitar 70-210, at least some lenses moved elements. I wonder how the optical formulae of the "shift elements" lenses differed from regular lenses and what the drawbacks were. – JenSCDC Sep 17 '14 at 20:13
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    @AndyBlankertz - there isn't any fundamental difference when you think about it; internal focus lenses essentially work by zooming while keeping the far end of the lens in place, and IF is sort of the default these days (where "unit focus" was the default in the past). It's still just a matter of using helicoids that are normally out of play, often because they did a lot of moving/shifting with relatively little rotation, so in addition to the extra effort, there would be a lot of extra stress/wear. – user32334 Sep 17 '14 at 22:11
  • True, but IF reduces focal length as the distance to the subject decreases. – JenSCDC Sep 18 '14 at 3:37

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