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09-10-2011, 12:34 PM   #1
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What kind of shots will i get with extension tubes on SMC Tak 135mm f/3.5?

I've never used extension tubes in my life and i wanted to achieve some form of macro shots, is it possible to do this with extension tubes?

09-10-2011, 01:21 PM   #2
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https://www.pentaxforums.com/forums/pentax-lens-articles/152336-cheap-macro-b...lose-work.html
09-10-2011, 02:18 PM   #3
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QuoteOriginally posted by kelvin.wong Quote
I've never used extension tubes in my life and i wanted to achieve some form .of macro shots, is it possible to do this with extension tubes?
Superb macros are possible (but not guaranteed) with extension tubes. An smc lens is a good starting place because of excellent inherent contrast and color. But you won't know until you try.

The best quality will likely be if the lens is mounted backwards (ie. "reversed" - that'll likely put more of the subject in focus).

To do this you'd not only need some $9 extension tubes but also a $11 "reversing ring" - for the PK 135:3.5 (49mm - PK)

I'd get two sets of tubes for the 135:3.5 (you'd only need one set with a shorter lens like an smc 50mm.)
Macro Extension Tube Ring Pentax K10D K20D K110D K100D | eBay

The reason you might want 2 sets of extension tubes is that change in magnification is proportional to extension/focal length change - 135mm is a fairly long focal length.

And a reversing ring...
MACRO REVERSING RING 49mm FOR PENTAX K NEW IN BOX | eBay
09-10-2011, 02:57 PM   #4
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Thanks newarts that really helped, also what does Raynox lenses do different?

09-10-2011, 03:30 PM   #5
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QuoteOriginally posted by kelvin.wong Quote
... what does Raynox lenses do different?
See the CHEAP MACRO article. Tubes push the objective closer to the subject and further from the frame (film or digital), so you get 1) a closer working distance, and 2) more magnification. Tubes are 'clean' -- they don't add any glass between subject and frame. Any extra glass there reduces IQ by some amount, possibly too little to matter. Tubes are cheap and easy. But long extensions also eat light, requiring longer exposures.

Close-up adapters, whether the cheap uncorrected +1+2+3 dioptre sets so widely available, or the corrected (and costlier) Raynox adapters, change the optic system properties, so a lens+Raynox has different focal length and focus range than the lens alone. They're rather like using a magnifying glass. The slight IQ loss of a Raynox is more than offset by its brilliant results. And they don't reduce the amount of light hitting the frame, so there's no need to worry about exposure time.

Advantages of extension (tubes and/or bellows): Clean, cheap, flexible -- it's easy to adjust the amount of magnification. Disadvantages: They eat light, and may not support aperture automation.

Advantages of close-up adapters, including Raynox: Very easy to use, and all automation remains intact. Disadvantages: Cheap adapters cut IQ; good ones, like Raynox, aren't real cheap -- about US$60-75 now.
09-10-2011, 03:51 PM   #6
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QuoteOriginally posted by kelvin.wong Quote
Thanks newarts that really helped, also what does Raynox lenses do different?
Raynox (or other achromatic or apchromatic) close -up lenses actually decrease the focal length of your lens; this in turn makes the images larger.A good rule of thumb is the magnification is (original.focal.length/close.up.lens.focal.length) So a 200mm lens with a 100mm close-up lens has a magnification of 2x.

One of the benefits of an add-on close-up lens like a Raynox is (unlike increasing magnification by extension tubes) the image remains bright.

A short-coming of an add-on close-up lens is the image will likely not be sharp on the edges - which usually doesn't matter for macro photos of natural subjects. See: https://www.pentaxforums.com/forums/lens-clubs/74221-raynox-macro-club.html

If you look at the images on the above Raynox Club link you will have difficulty finding one where edge sharpness mattered.

I own a couple excellent macro lenses as well as tubes, bellows, special enlarger lenses, etc. But mostly I use my Raynox DCR 150 on a long zoom for macros. It is always in my kit "just in case". It is small, lightweight, quick to mount, maintains all lens & flash automatic functions, and with my 55-300mm zoom lens covers essentially all magnifications it is practical to hand-hold. It has a working distance (lens-subject distance) of about 8" which is good for bugs etc and gives a bright viewfinder image..

I think it is the most cost-effective (~$70usd), instructive, productive way to begin macro-photography.

I would only caution against a Raynox type lens if your subject would be stamps, integrated circuit guts, or something equally flat.
09-10-2011, 04:37 PM   #7
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QuoteOriginally posted by RioRico Quote
and 2). . . more magnification.
I believe this commonly used explanation causes unnecessary confusion.

A lens at a given focal length (FL) and focus point never changes its inherent characteristics. How much of the image that's projected behind the lens that is "intercepted" by a given sensor may make it seem as though the lens has somehow physically changed its magnification factor though.

Extension tubes move the lens forward making the 'intercepted image' at the sensor seem as though it's somehow "magnified" because less of the subject is captured in the FoV. Rings (or bellows) also change the range of sharp focus and the apparent depth of field available with a given lens.

(Adding extension tubes equal to the focal length of the lens will generally provide a 1:1 magnification ratio. Greater or lesser extension is directly proportional. The same effect is true of variable extension bellows.)

The same situation applies to the "cropped" APS-C sensor, except that it's the smaller size of the sensor area within the projected FoV of the image that makes it seem "magnified". Conversely, if we placed a larger sensor in the projected FoV it would appear as though the lens was de-magnifying the image and seem as though a wider angle lens was used.

Positioning the lens farther from the sensor and, to a very small extent, intercepting less of the image, causes a reduction in the amount of light striking the sensor/meter and a necessary adjustment in exposure. The change in average light values within the image made available to the metering system will affect the correct exposure setting as well.

Draw a flattened 'X' representing the lens and its light rays and vary the size and placement of the "sensor" in the projected FoV to see this effect. Note that the lens itself doesn't physically change (unless it's re-focused). Make the 'X' "wider" or "narrower" to simulate WA or tele lenses in the same scenarios.

Using front placement magnifying filters is similar to looking through a magnifying lens and being more or less universal they can't accommodate the inherent characteristics of individual primary lenses with a subsequent reduction in potential image quality.

One way to slightly enhance the fringe performance of front magnifying lenses is to only use the center portion of the glass by employing step-up rings and oversize accessory lenses.

H2

Last edited by pacerr; 09-10-2011 at 04:44 PM.
09-10-2011, 06:04 PM   #8
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Yes, you'll be able to get macro shots with extension tubes. If you add 50mm of tubes you'll get close but not super close macro shots. It would be a 1:2.7 macro, right? This will be a HUGE improvement over the 150mm min focus distance that you currently get tak135/3.5. And probably a very good butterfly lens.

The problem is that your lens starts getting longer and heavier. And you'll need good lighting. But this is true of macro in general.

The nice thing is that you can put the same ext tubes on a fast fifty (or other lenses) and get really close.

The problem with the reversing ring is that you will be really close to whatever your photographing. Like a few inches. Great for some things and impossible for others.

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