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04-13-2011, 08:03 AM   #1
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Define "Macro Lens", please

how can a lens be labeled "macro" if the nearest focal distance is 0.45 meters (or so) from the subject?

My Tamron 18-200 is listed as a macro lens, but if I get close enough to what I feel is "macro", even at a zoomed focus, I cannot get an actual focused image.


I appreciate the education I am about to receive. Amen.

04-13-2011, 08:19 AM   #2
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The close focus range on a longer lens will be much further away from the subject than on a shorter lens. I'm not familiar with your Tamron but the "macro" range is probably at the long end of the zoom. This is handy sometimes when you can't get too close (bees and other insects). The term "macro" is used very loosely. There are others who can give a much better technical explanation than I can. A true macro has 1:1 magnification and very little or any curvature and sharp from edge to edge. There are others who I'm sure will give a much better technical and detailed explanation.
04-13-2011, 08:20 AM   #3
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Macro has nothing to do with distance from the camera to the subject. Macro is defined by magnification. A true macro lens is typically a magnification of 1:1 - this means that the lens is projecting an image onto the sensor that is physically the same size as the sensor itself (example: if the sensor is 1 inch squared, then the image a 1:1 lens projects will be 1 inch squared). Lenses that are 1:2 are still considered macro, though the image (area) projected on the sensor would be twice as large as 1:1.

Sigma and Tamron tend not to exaggerate, but loosely define lenses that are 1:3, 1:4 even 1:5 as macros, even though the lens is only capable of covering an area 3x, 4x, 5x (ETC) the size of the sensor onto the sensor itself.

Below are a couple of examples I took using the same 50mm lens to give you an idea of what 1:1 means. the first is the 50mm lens on a pentax 1.5x crop sensor, the second is the same lens on a micro 4/3 camera which gives 2x crop. Since the micro 4/3 sensor is smaller, the actual image ends up appearing to be a closer macro, but both are actually still 1:1 as defined by the lens, since the area of the micro 4/3 sensor is smaller.

Hope that makes sense, apologies for my long-winded-ness!



04-13-2011, 08:21 AM   #4
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Wheatfield's definations are spot on, but I'd like to add that most lens makers will add a "macro" designation to a lens even tho it is only "close focusing". Typical of market speak everywhere for every product, the definations and boundaries get blurred. Your Tamron is a good example. It can focus closely, but in no way is it a "real" macro.

NaCl(a "macro" zoom lens is like a 4 door "sports car" )H2O

04-13-2011, 08:45 AM   #5
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Think of it this way, in general terms....

If your sensor/film is 1 inch square. An object that is the same size at 1:1 magnification will completely fill that 1 inch square sensor. 1:2 will fill half of it. 1:4 will fill one quarter of it. Speaking of quarters, here are 4 shots done at 1:1, 1:2, 1:3, and 1:4 with a 100mm macro lens.

Index of /Photos/HelpandStuff/100mmf28WR

The actual focal length of the lens does affect how close you need to be to your subject to get 'true' macro. With a 35mm 1:1 macro for example, you must get closer to your subject than with a 100mm macro to get the same magnification. With your 18-200, I'm willing to bet that you can only do Macro (close focus) at the longer end. With the Tamron 70-300 I use to have, close focus was only possible from 180mm to 300mm. That lens claimed to be 1:2 macro capable. There are a few examples from that lens here.

Show Tamron - a set on Flickr

To Further expand.. Macro lenses are usually designed to give not only very close focusing ability but also to minimize or even eliminate distortions. You can set your Tamron to 18mm for instance and get pretty close in your focus, then crop the resulting photo, and get something that looks macro-like. It will however, be distorted somewhat.


Last edited by JeffJS; 04-13-2011 at 08:51 AM.
04-13-2011, 09:32 AM   #6
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I think there are 2 real distinctions to be made here, with respect to the true meaning of macro.

the first is the ability to provide magnification in the order of 1:2 or better, and the second is that true macro lenses are designed to be flat field lenses, i.e. they will focus perfectly across the entire frame, on a flat subject, where as normal lenses actually focus on a curve (although usually very large radius and therefore approaching flat)

In the late 1970's especially, many zoom lens manufacturer's began marking their lenses as macro, as wheatfield describes, when they could achieve a magnification ratio of 1:5 or better.

This use of "macro" has existed ever since, and has mutated further to describe close focusing, because that is how it is achieved, however, these lenses are NOT flat field lenses.

Being Flat field really only applies if you are photographing flat subjects, such as stamps, coins, etc, because you may want exact focus without stopping down. A curved field lens would require stopping down to ensure a flat object is all in focus.

For most people, flat field is not an issue, Flowers and bugs are not flat (except when stepped on or when viewed on a windshield)
04-13-2011, 09:42 AM   #7
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QuoteOriginally posted by reeftool Quote
The close focus range on a longer lens will be much further away from the subject than on a shorter lens. I'm not familiar with your Tamron but the "macro" range is probably at the long end of the zoom. This is handy sometimes when you can't get too close (bees and other insects). The term "macro" is used very loosely. There are others who can give a much better technical explanation than I can. A true macro has 1:1 magnification and very little or any curvature and sharp from edge to edge. There are others who I'm sure will give a much better technical and detailed explanation.
The definition of macro is complicated. Like the judge who struggled to define obscenity, saying, "I know it when I see it." I think a lot of technical explanations get tied into knots trying to include certain lenses and exclude others. I would just leave it at Reeftool's explanation.

Here is why we make an effort to include some lenses and exclude others. Last year I had two lenses with a 1:2 magnification ratio. One was a Tamron SP 90mm f2.5 Adaptall-2 macro lens, model 52BB. The other was a Quantaray 70-300mm f4-5.6 zoom, a rebranded lens also made by Tamron. I took a $20 bill, taped it to a wall, set up my camera on a tripod, moved it until the bill was as large as possible in the frame, and took shots at different apertures. Here are 100% crops from the test photos:

Centers

Corners

The 90mm lens is clearly better. You can see the flatter field and edge to edge sharpness. It's also better at wide apertures. Now, to get the same size image, I had the camera at 15.5 inches away for the 90mm, and 37 inches away for the zoom. Balance is also completely different, with a lot of the zoom sticking out. I think these examples show why people want to separate these lenses into different classes.
04-13-2011, 10:07 AM   #8
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I'll add that the longer zooms have their value. I have the Sigma 70-300, also labeled a macro and similar to the Tamron/Quantaray and it works very nicely on the water from my kayak getting close-up shots of insects, flowers,etc. Actually, my copy has far better IQ in the 200-300 range as a "macro" than as a telephoto.

04-14-2011, 03:38 PM   #9
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Just a couple hours ago, I brought home my third 'macro' prime lens, an ancient immaculate Kilfitt Makro-Kilar 40/3.5 E, possibly the first-ever macro lens for 35mm SLRs. The 'E' model reaches 1:2; the 'D' model reaches 1:1. My other two macro lenses, both in M42 mount and reaching 1:1, are the Macro-Takumar 50/4 and the Vivitar-Komine 90/2.8 macro. I also use a number of enlarging lenses on bellows or tubes for macro shooting.

These macro primes, and the enlarger lenses, are specifically designed for close work, with edge-to-edge flatfield sharpness. "Macro-zooms" are NOT designed for close flat work (except my Schneider Betavaron 50-125 enlarger zoom, which is a whole 'nother thang). IMHO, zooms are labeled MACRO because that uses less ink than CLOSE FOCUSING.

Almost any lens can shoot in the macro range, often defined as 1:2 or greater magnification, by adding extension to the lens, such as tubes or bellows. Results may be quite good if corner and edge sharpness aren't important. If the image margins ARE important, use a flatfield lens.

Ah, but there is an easy way to make almost ANY lens a flatfield macro: reverse it. The small end of a lens *IS* designed to deliver a flatfield image, to the frame (film or sensor). The problems with this approach are 1) Working distance is very very close, and 2) Aperture control is manual, making flash usage tricky. Lens-reversal is easiest with lenses with manual aperture rings.
___________________________________________________________________________________________

EDIT: A dumb-ass question: What optical formulae are flatfield? I read that my new Makro-Kilar is a Tessar, that the only difference between the D (1:1) and E (1:2) versions is the amount of extension in the helicoids. It looks like my Macro-Takumar 50/4 is a Tessar. I read that the Industar-50/3.5, much-beloved for cheap macro on tubes, is a Tessar. I haven't researched enlarging lenses, but many are quite small, just a few elements -- are they all (or mostly) Tessars? If many flatfield lenses are Tessars, does that mean that most or all Tessars would work well in macro settings? Have any optics gurus here got an answer?

Last edited by RioRico; 04-14-2011 at 05:20 PM.
04-27-2011, 10:44 AM   #10
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Even I wanted to ask the same question since I hold 35mm f/2.4 and in the lens database section there are 2 variants one is 35mm f2.8 called a macro and then there is my lens which is also 35mm but with f2.4.
04-27-2011, 10:52 AM   #11
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And the latter is not a macro Magnification approximately 1:6 (see the specs on SMC Pentax-DA 35mm F2.4 AL Reviews - Pentax Lens Reviews & Pentax Lens Database)
04-27-2011, 11:11 AM   #12
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I'll also mention a couple of 'macro' primes that seem to employ the "macro-zoom" trick of extending the front element to get into close-focus mode. A Sears 135/2.8 (#86xxxxx, KR mount, sold) and an Access AMC Macro WA 28/2.8 (#82xxxxx, KM mount, kept) both allow the objective to be dialed-in for closeups. I think the Sears went to 1:4; the Access has settings for 1:37, 1:4, 1:5, 1:5, and Normal. Neither are flatfield; both just let you shoot a bit closer. Cheap trick, eh?
04-27-2011, 11:12 AM   #13
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To get really picky I believe a good macro lens must be designed not only to have a flat field at the image plane but also have a flat field at the object plane and be sharpest at whatever magnification (distance) is appropriate for the lens in question (for example a 1:1 macro lens should perform best at 1:1 magnification).

I am a learner here and did not realize 'till recently that lenses are designed to be optimum at a particular distance from a scene (often the hyperfocal distance for "normal" lenses I think).

While most lenses are designed to have a flat field at the image plane I doubt that means that when reversed they'll have a flat field at the camera's image plane (because what's now the camera's image plane was the object plane as far as the original lens design is concerned... and most likely the designers assumed the object plane was far away.)

Good enlarger lenses on the other hand expect to have both image and object planes that are flat and close-by.
04-27-2011, 06:33 PM   #14
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QuoteQuote:

With your 18-200, I'm willing to bet that you can only do Macro (close focus) at the longer end. With the Tamron 70-300 I use to have, close focus was only possible from 180mm to 300mm. That lens claimed to be 1:2 macro capable. There are a few examples from that lens here.

so my 80-200mm "macro" that only close focuses at the short end is the exception not the norm?
at 80mm it can turn extra to close focus

thanks
04-28-2011, 10:57 AM   #15
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QuoteOriginally posted by sterretje Quote
And the latter is not a macro Magnification approximately 1:6 (see the specs on SMC Pentax-DA 35mm F2.4 AL Reviews - Pentax Lens Reviews & Pentax Lens Database)
Exactly! that is the reason I mentioned it here except for the aperture it is the same focul length - so what makes one a macro and the other a normal lens.
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