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04-22-2011, 08:33 AM   #1
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macro tube vs macro lens

Hi, I've been wondering what the benefit of a macro lens is over using macro extension tubes with a standard lens like a 50mm f1.4 prime?

Apart from the fact that with the tubes I have to focus by moving the camera and that I lose the auto settings, are there other benefits to using a macro lens?

Thanks.

04-22-2011, 08:45 AM   #2
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Aside from being easier to work with since the lens itself will focus whereas with a tube your movement is needed to focus. A true macro lens will generally produce sharper and brighter pictures as it is specifically setup for macro photography. However, this should not be confused with Sigma/Tamron and other manufacturers definition of macro in the case of the 70-300 where they slapped on macro but only does 1:2 or 1:3.

Other than that I have no more help. Perhaps someone more technically inclined can help out here.
04-22-2011, 09:48 AM   #3
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For simplicity's sake, imagine a macro lens as a normal lens with built-in tube. The tube goes into action "automatically." That means the lens can focus from very short distance (for macro shots) to infinity and in between. You don't have to remove/attach the tube.

Also, because of the special application, macro lenses in general are built with better materials and have tighter QC than normal lenses, at least in the old days.

Notes:

- With a tube and a normal lens, you can still focus with the focus ring of the lens. The range is limited, however.

- Even with a macro lens, at macro distances, many times it's easier to focus by moving the camera back and forth than by using the focus ring of the lens.

- Using extension tubes doesn't necessarily mean losing auto settings. If the tubes have electrical contacts, auto metering modes (P, Av, .....) are still possible. Examples (the one on the right is a gutted teleconverter):


Last edited by SOldBear; 04-22-2011 at 09:59 AM.
04-22-2011, 10:32 AM   #4
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Flat field

Consider that the "plane of exact focus" for a lens isn't a flat plane but the inside surface of a sphere. At normal distances and a reasonable depth of field (DoF) this isn't too critical (although many discussions of sharp focus overlook this point). Now consider the critically thin DoF at "macro" distances. Think of the actual focal distance as the radial distance to a curved surface covering the field of view rather than to a fixed, flat plane.

Not only does a macro lens incorporate the convenience of a continuous focusing extension ring while maintaining the ability to focus to infinity, the better macro lenses include a more complex optical formula to help "flatten the field" of critical sharpness as it's focused on the sensor. This is also one of the factors involved when reversing a lens for close-focus use and the utility of "flat-field" lenses for copy work.

This additional optical complexity can be accommodated relatively economically in prime lenses but becomes impractical for zoom lenses with present technology.

You can wish for a future lens that's electronically controlled to follow-focus on the topography of a scanned surface as used in certain LASIK instruments today. Of course it'll have to also understands the difference between your target and the background/bokeh too. Start saving your pennies now though.

H2

04-22-2011, 11:55 AM   #5
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To summarize a bit: Real macro camera lenses are usually exceptionally well-built, and are designed for edge-to-edge flatfield sharpness. Virtually NO "macro-zooms" meet those criteria. Many non-macro camera lenses also don't qualify. If your subjects are rounded, and/or edges aren't critical, then no matter. If you're shooting postage stamps, microcircuits, other flat stuff, then it matters.

Macro camera lenses --
PROs: Construction, image quality, ease of use (aperture automation and flash, etc).
CONs: Money, money, money; macro camera lenses aren't cheap.

Camera lenses on extension --
PROs: Flexibility. And money, money, money; simple extension is cheap.
CONs: Money, money, money; fancy extension isn't cheap.

You could mount an AF lens on AF tubes (or de-glassed AF teleconverters). Those aren't cheap, and AF isn't necessary with CLOSE macro work. You could mount AF or A-type lenses on cheaper A-type tubes or deglassed A-type TC's. Either of those options retains aperture automation and thus allows stopped-down metering and shooting, and easy flash.

You could mount any lens with an aperture ring on cheap simple tubes or bellows. Or even lenses without aperture rings, if you don't mind shooting wide-open. These include camera lenses, enlarger and projector lenses, or any optical material that will fit. I like cheap enlarger lenses (EL's) for their edge-to-edge flatfield sharpness, and cheap projector lenses and lenses scavenged from old medium-format cameras for their character.

So, a great advantage of tubes (or bellows, for more flexibility) is that you're not limited to the constraints of an expensive macro lens. You can use good camera lenses close-up. Some cheap lenses are legendary here, such as the Industar-50/3.5. You can use whatever cheap lenses you have. If they are enlarger lenses, you'll get results no worse than expensive camera macro lenses. You just need to take responsibility for the lighting.
04-22-2011, 01:07 PM   #6
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go for multiple options

I think over time you will go for multiple options, as I have.

I started with a vivitar series 1 70-200F3.5 zoom lens that could go to 1:2.2 (at 70mm focal length)

while that was a nice lens, the zoom suffered badly from zoom creep due to construction and had no tripod mount for the lens although it weighs in at 900+ grams (2 pounds for the metric impared) but for close focus when travelling, to avoid carrying another lens, it made some sense. Hold that thought.

Then I went for an SMC-M 100mm F4 macro, which goes to 1:2 without extension tubes, and past 1:1 with the 68mm 3 tube set I can stack together. the pro's it is light, and a good sharp lens. the cons, really only the extension tubes to get to 1:1. The real down side is you need to use a tripod and focusing rail for a lot of it.

then, I went to a bellows. I have an old miranda bellows that I have converted to a K mount rear attachment, and it has a miranda 44mm x 1 thread on the front. I have also a T mount adaptor, mirand aextension tubes, an M42 to t-mount adaptor, M42 extenision tubes, plus a 135mmF4.5 enlarger lens cemented into a T mount adaptor. the long and short of it is, I can use the bellows, with or without any extension tubes, or I can stack about 70mm of extension tubes in front, and mount my 135 mm lens, and get to 1:0.75.

I can also mount to this the M42 adaptor, another 57mm of M42 extension tubes and any M42 lens I want, including my 50mmF4 SMC-Maro Zak and get to about 1:0.2

The advangate of the bellows other than magnification is flexibility. with the 135 enlarging lens I can even attain infinity focus if I want. the down side is big and cumbersome

But, when I travel today, I leave my macro stuff at home, I pack my 28-75F2.8 tamron which can close focus to about 1:3, While not macro, and not a flat field lens, it is there for quick close ups.

The bottom line is macro takes time and is combersome, and sometimes you want the ability to get reasonable reproduction ratio, between say 1:5 and 1:3 and not have to worry about lugging all the stuff around, so keep in mind that regardless of the final macro kig, lens/ bellows extension tubes, focusing rails etc... you should always have one zoom that can close focus in a pinch as well
04-22-2011, 01:09 PM   #7
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for me....

reversing lenses on tubes > macro lens
04-23-2011, 01:23 AM   #8
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QuoteOriginally posted by yeatzee Quote
for me....

reversing lenses on tubes > macro lens
And that's another point -- I didn't mention it above because 1) I'd written about it on other threads and 2) I got lazy. Yes, all camera lenses (that aren't utter trash) gain flatfield sharpness when reversed. The PRO: All that sharpness, for no extra money! The CON: Working distance for primes is around 4.5cm, under two inches. That's OK for studio shooting, but kinda cramped for field work. Bother.

But wait! There's more! Reversed zooms act a bit differently. I diddled-around the other day with my lowly A35-80, arguably one of the crappiest lenses Pentax ever sold. I reversed it, using a simple 49mm-PK mount-reversal ring. At 35mm it reaches 2:1 magnification at about 5cm distance. At 75-80mm it focuses out past infinity, and reaches 1:2 down at about 15cm distance. And it is quite sharp, reversed! A bit of fringing at extreme high-contrast edges, but otherwise pretty decent.

And that's with a crap lens. Better zooms should give better results. So I tried my Promaster-Tamron 28-70 (FF-AF) on a 58mm-PK reversal ring plus 52-58mm step ring. It didn't reach infinity focus at 70mm -- that step ring adds enough extension to pull far focus down to about 27cm -- but I don't see any fringing! I also tried a couple older push-pull zooms, but they are sloppier to use than more modern zooms with separate zoom rings. Just make sure your zoom has an aperture ring, and it'll make a dandy macro lens! As with any lens, more extension gives more magnification.

NOTE: You can use CIF (catch in focus) with mount-reversal rings. Don't try the metal tape trick. The tape adds enough thickness to jam the adapter on the camera mount. Instead, scrape or file away the adapter's black paint in the appropriate location, to safely short the contact pins on the camera mount. And where is that location? Just opposite the red dot (index mark). Looking at an adapter: With the red dot at 12-o'clock, remove paint between 5-6-o'clock.


Last edited by RioRico; 04-23-2011 at 01:32 AM.
04-23-2011, 02:21 AM   #9
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I have seen no evidence that a lens designed and and marketed as a macro lens performs any better that a good prime lens on a tube for macro photography of natural subjects.

If such evidence exists I'd love to see it!

The "for macro photography of natural subjects" qualification is as important as the "I have seen no evidence" qualification. There is a really good chance that field flatness issues may be an important distinction between high quality special purpose macro lenses and regular lenses used for macro work; even so it hardly matters for non-flat subjects because depth of field is so thin that natural (non-flat) subjects will be out of focus at the edges regardless of lens field flatness.

RioRico makes a reasonable case that reversed lenses may have better flatness characteristics for macros because the subject will be positioned where the lens designers thought a flat film plane would be. However, those same lens designers also assumed the flat image requirement was needed when the subject was quite far from the lens - certainly not as close to the lens as in the case of a reversed lens.

Pacerr addresses the same flatness issue well.

Flatness will be an important issue for certain subjects like integrated circuits, stamps, ground & polished technical materials etc. If flat subjects are of interest to you then perhaps you should think about seeking lenses designed for the purpose.

This forum has a long thread showing superb macro images taken with Raynox brand close-up adapters on a variety of lenses. See: https://www.pentaxforums.com/forums/lens-clubs/74221-raynox-macro-club.html here's an example http://img41.imageshack.us/img41/3838/004sb.jpg


But here's a test that looks at the effect of the Raynox 150 lens on the flatness and sharpness at the edges of the field when it is on a good macro lens (without the Raynox the edge-edge focus is excellent):

As you can plainly see the poor edge definition probably caused by the Raynox for the Bee photographer had no practical effect on the image of the Bee shown above.

In conclusion I think the tube/prime lens approach may work as well as a dedicated macro lens for natural 3D subjects but maybe not for flat subjects.

Last edited by newarts; 04-23-2011 at 02:27 AM.
04-23-2011, 02:43 AM   #10
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Grateful thanks to all contributors - that was a highly informative thread.

I am using Fotodiox tubes - no electrical throughput on these. But the brilliant Pentax green button in manual mode meters very well indeed.

I have in the meantime tried the standard Pentax 18 - 55mm zoom vs. my very old Ricoh XR F2 50mm. The Ricoh gives virtually no focus adjustment with the focus ring and of course DOF is very short.

The 18 - 55mm standard kit zoom on the other hand has been revelatory - the zoom and focus ring can both be used to fine tune a focus setting.

With this lens, I have to jam the aperture lever into the open position.

Following comments above, I'm going to try the zoom lens with a reversal ring next.

And my next project will be to make a ring light from leds to fit around the lens barrel.

Regards.
04-23-2011, 04:11 AM   #11
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QuoteOriginally posted by jlaubza Quote
With this lens, I have to jam the aperture lever into the open position.

Following comments above, I'm going to try the zoom lens with a reversal ring next....
Here's a trick you can use to position the kit lens aperture where you want it for macro work: use a short piece of plastic or rubber tubing over the aperture lever. Friction between the tube and the aperture lever protection shield will hold the aperture in place. Then you can focus with the lens wide open & close it down a bit for the exposure to get better dof & image quality.

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