Macro on zoom lenses

Hello.

There are several zoom lenses that offer 'macro' capabilities which allow the user to get closer to the object than the normal setting.

My question is, "how different is 'macro' from the normal range from the mechanical point of view?"

It seems like that "macro" on these lenses simply lets you rotate focus ring (or zoom ring) further so that you go beyond the minimum focus distance and nothing more. Then why wouldn't the manufacturers mark the lenses to just have that much normal range?

For example my lense has 1.5-oo normal range and probably something like 0.6-1.5 macro range at the widest angle. Then why can't they specify it as just 0.6-oo if there is no special distinction between "normal" and "macro" in terms of mechanical construction?

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Thanks!

So, you've noticed the difference between a true close-focusing zoom

design and the gimmicky "macro feature." First, most macrophiles

consider a minimum of 1:2 magnification necessary for a lens to

qualify as a macro. Few zooms do better than 1:3.

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There's no simple answer to your questions and, frankly, I'm no expert

on lens design. But the essential differences have to do with how the

various elements in the zoom move in relation to one another.

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In the good old days lens makers knew that it was prohibitively

expensive to build a true close focusing zoom. So many of them opted

to build varifocals, a design that requires refocusing as the focal

length is changed. (In fact, some of today's autofocus zooms are

varifocals, but nobody notices because of the AF feature.) The

advantage is that while the user must refocus (only slightly), few

optical compromises are made.

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My Vivitar Series 1 28-90mm f/2.8-3.5 is one such design. It focuses

reasonably closely at all focal lengths, but achieves maximum

magnification (around 1:3, but I haven't measured it) at 28mm, which

makes for some odd looking close ups thanks to wide angle barrel

distortion. Still, it's an excellent lens overall, sharp at the

center at all focal lengths and focusing ranges, and sharp out to the

edges everywhere beyond 50mm at minimum focusing range.

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To put it simply, it's the best zoom I've ever owned in terms of

optical quality and value. There are better zooms, but not at this

price.

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The next step, also common with some Vivitar designs, was the zoom

that was close focusing only at one focal length. The best bargain

among these was a 70-210mm f/4.5 - not the fancy, expensive Series 1 -

that achieved 1:2 magnification at 210mm. Pretty good, because you

didn't have to get so close to those bitey, stingy, irritable bugs and

critters. At all other focal lengths it would focus to 6 feet or so.

Besides being a nice, compact design, you can sometimes find these

zooms for $50 or less.

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Finally was the ghastly design incorporated by even reputable lens

makers like Canon and Tamron, in which a separate ring was twisted, or

a button was pressed to permit focus ring overtravel, to achieve

"macro" focusing at the minimum focal length, 70-75mm. These designs

shifted an element inside the lens to permit close focusing - but not

true macro - within a limited range. To regain infinity focusing

you'd have to press that button and disengage the macro "feature."

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Frankly, these designs stink. I've owned both the Canon and Tamron

zooms in the 70-210mm range with this macro feature and while the

Tamron was a much more sturdily built lens, it still stunk close up.

Both were okay beyond 10 feet and out to infinity - even pretty good

at some ranges, focal lengths and apertures. But macro? Gimme a

break. Coma, spherical distortion, you name it, they got it.

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Ironically, the macro magnification of these designs - roughly 1:4 -

could be duplicated by simply focusing to the minimum distance at

200mm. No need for the "special macro feature." And the results were

the same. They stunk. Few telephotos are at their best focused

closer than 10 feet.

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A variation of the close focusing design is my Canon FD 100-300mm

f/5.6 non-L series zoom. It close focuses from 100-200mm, achieving

maximum magnification at 200mm, and is quite good. It's a delightful,

if oversized, portrait lens. Beyond 200mm it's good only when stopped

down, otherwise it suffers from poor contrast and resolution.

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In short, skip any zoom lens with a special macro ring, pushbutton or

doodad that must be set to get close ups. Go for a varifocal or a

true close focusing design, especially one which close focuses at the

longest focal length.

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But for the best bargain in macro doodads, get a Vivitar 2x macro

focusing teleconverter. It's a top quality teleconverter and achieves

1:1 magnification. Combine it with a 50mm f/1.4 normal lens and

you'll have a very good quality 100mm f/2.8 portrait lens that focuses

1:1 while giving you comfortable distance from the bitey, stingy

critters.