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07-15-2009, 03:33 AM   #1
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Noob Question Difference Between a Lense That Does Macro & A True Macro Lense

Well as the title says, I'd like to understand the difference.

Ie I have a 17-70mm Sigma that does Macro but how would it differ from a TRUE macro?

cheers

07-15-2009, 04:02 AM   #2
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A lot of companies have a "macro" option on their lens, which means that the lens has some close focusing ability. A true macro should give a 1:1 (at least) reproduction of the object (bug, flower) on the sensor. I don't know if the 17-70 can do that, but probably not.
07-15-2009, 05:11 AM   #3
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What ^^^ they ^^^ said.
07-15-2009, 06:16 AM   #4
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A "true macro" is loosely defined as a lens achieving at least a 1:2 magnification ratio. Your Simga does 1:2.3. Close, but no cigar.

A Pentax 50mm Macro does 1:2, but comes with an extention tube to allow 1:1. Most macro lenses of longer focal length can achieve 1:1 without a tube.

07-15-2009, 06:57 AM   #5
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QuoteOriginally posted by C.W Tsorotes Quote
Well as the title says, I'd like to understand the difference.
You could read this Wiki article, the second paragraph in particular may answer quite well your doubts:

Macro photography - Wikipedia, the free encyclopedia
07-15-2009, 07:37 AM   #6
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Thanks for that, doesn't mention anything about lenses in regards to flat DOF etc.

Still is a bit confusing how does a macro 50mm lense differ in operation from a standard 50mm for example if I were to be shooting portraits.
07-15-2009, 10:10 AM   #7
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Most lenses (not 'true' macro) can only focus down to mag. ratio 1:8 (image on sensor 1/8 size of real life). The minimal focusing distance is about 10 times the focal length (e.g. 0.5 meter for 50mm lens).

(True) macro was then defined to be a lens with minimal mag. ratio of 1:2. These macro lenses require higher tolerance & better materials in manufacturing. As a result, they are high quality in general, not just when taking macro photos. Having flat field is part of the high quality.

Around 1980s on, many zoom lenses started having max. mag. ratio of 1:4. Some even approached 1:2. The marketing department, true to their motto, "if you can't convince the consumers, confuse them," decided to call these lenses 'macro.' It sounds better than 'close focus.'

If you are shooting portraits (focusing distance is greater than 10X the focal length), a 50mm macro is no difference from a 50mm 'non' macro. The difference, if any, is related to the general quality between the two lenses.

(Some macro lenses designed for optimal quality at close focusing distances, giving up quality at greater distances, but these lenses are few).
07-15-2009, 10:19 AM   #8
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QuoteOriginally posted by C.W Tsorotes Quote
Thanks for that, doesn't mention anything about lenses in regards to flat DOF etc.

Still is a bit confusing how does a macro 50mm lense differ in operation from a standard 50mm for example if I were to be shooting portraits.
no difference at all when shooting portraits. they call it macro because of the magnification or close focusing ability of the lens that a normal 50 cannot perform. though it may appear that the 50mm macro is a bit better in IQ. unless they make a Macro with a 1.4 speed, then the FA 50 1.4 has seen it's last days.

07-15-2009, 11:50 AM   #9
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QuoteQuote:
A Pentax 50mm Macro does 1:2
The Pentax FA and DFA 50s give 1:1 macro enlargment.

A true macro is indeed 1:2 or better, as others have said. Macro lenses also offer much lower distorsion figures, are generally more evenly sharp across the frame than regular lenses, are usually almost as good wide open as they are at smaller apertures. They SHOULD (and I can testify that my FA 50 does) give amazing contrast. They offer a long focus throw for precise focus control.

Generally speaking, the macro lenses are the best at most things. They come at a price for a reason.
07-16-2009, 09:45 AM   #10
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A 50mm lens is a 50mm lens. If it's labeled "macro", that means it can focus from a closer distance than non-macro 50mm lens - focusing close is how a macro lens gets it high magnifications. So the macro would let you shoot a bug at 4 inches (more or less) away, yielding a large image, but the nonmacro would force you to shoot form a foot or more away, yielding not nearly as large an image. But when shooting portraits from the same distance away, the images are identical.

Summariing the difference betwene "true" macro and just "mostly" macro. Some define true macro as 1:1, meaning you can focus closely enough to render a one-inch-long object one inch long on the sensor. Since the sensor is about one inch long itself, that makes it easy to describe this in practice: you're getting 1:1 magnification if a one-inch-long object fill the width of the viewfinder. Some stretch the definition to allow for 1:2 magnification, meaning atwo-inch-long object would fill the viewfinder at closest focus distance. That's obviously not as much magnification, but it beats most other lenses.

Aside from that, lenses designed to be true macro lenses that *also* tend to have flatter planes of focus, also tend to be optimized to yield best results at those close distances, etc, but there's nothing written in stone about any of that.

So basically, your 17-70 zoom will not let you focus close enough to ake an inch-long-object fill the viewfinder - it would take a 2.3-inch-long object to fill it up. So it's slightly better than the kit lens, which is 1:3 (a 3-inch-long object can fill the viewfinder), but less than half as good as a 1:1 macro.
07-18-2009, 01:16 AM   #11
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Cheers I had a play with a D FA 50mm Macro lastnight really liked the results it gave, but was quite pricey.

I hear Sigma does a nice 70mm Macro to?
07-18-2009, 02:17 AM   #12
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QuoteOriginally posted by C.W Tsorotes Quote
Thanks for that, doesn't mention anything about lenses in regards to flat DOF etc.

Still is a bit confusing how does a macro 50mm lense differ in operation from a standard 50mm for example if I were to be shooting portraits.
Actually that's a quite good article on macro photography. Perhaps you are not much on to reading.

BTW, the article explains the basics of Depth of Field considerations on macro, even gives you a tip about using Photoshop to combine different FL shots, in order to compensate the shallow DOF of a macro lens.
07-18-2009, 05:01 AM   #13
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It seems to me that common wisdom we repeat about what constitutes a "real macro lens" with its emphasis on magnification is misleading to the naive user.

If I take a normal 50mm lens and put it on a 50mm extension tube so the magnification is 1:1 does that make it a "real macro lens?"; no, I have just moved into the macro magnification range with a non-macro lens.

The essential factor distinguishing a marco lens is that it is designed to give a flat, rectilinear image at small working distance.

As evidence of this distinction, consider the existence of "macro lenses" with no focusing mechanism at all (ie. intended for bellows use); such lenses are true macro lenses whether they are on the bellows or not.

"Magnification" is quite misleading when talking about P&S & Bridge cameras to casual users, as what most people really mean when thinking about close-up photography is the size of the displayed image, in which case width of field is a more appropriate measure.

"For a particular width of field & f-stop, depth of field is proportional to crop factor" is a lot easier to grapple with than the equivalent explaination cast in terms of magnification.

That said, I continue to use normal lenses at magnifications around 1:1 and think of it as "macro photography" even though I've used a non-macro lens.

A Dave in Iowa

PS there is good reason to refer to photography with a magnification of 1:1 or greater by a different name - the mathematics relating image characteristics (like exposure time, depth of field, etc) contain a multiplicative term like (1+1/m) - this term is important when m is much less than 1 but insignificant for large magnifications. This detail is of little use to someone who just wants to know if his/her camera can take a good photo of a fly.
07-18-2009, 02:14 PM   #14
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real macro lens is different from a makeshift macro that uses bellows, extension tubes, reverse rings , etc...

real macro lens are built specifically as to the thickness and geometry of the lens itself. a clear example of this is the magnifying glass. magnifying glasses have certain thickness and geometry inorder to achieve that certain magnification at a certain distance. now this magnification would produce a certain flat or rectilinear image as some here had pointed out. the DOF in a true macro is different as compared to a makeshift macro by virtue of distance and magnification power. makeshift macro lenses tried to duplicate this by increasing distance in the expense of having a very thin DOF. again this is because of the nature of the lens itself.

a macro lens + an extension tube would create more magnification and flat DOF as compared to a normal lens + an extension tube.

Last edited by Pentaxor; 07-18-2009 at 02:19 PM.
07-18-2009, 03:53 PM   #15
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When using a standard 50mm lense in reverse config how is that compared to using a true macro?

Aside from the AF/apperture control etc?
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