Macro lens - 1:2 = 1:1 on MFT?

Discussion in 'Adapted Lenses' started by chicks, May 25, 2012.

  1. chicks

    chicks Mu-43 Top Veteran

    876
    Feb 1, 2012
    The Big Valley, CA
    So, I recently picked up an SMC Pentax-M 100/4 Macro lens. It's a 1:2 macro. Will the crop factor on my E-P2, which effectively doubles the length, also double the macro magnification? Seems to make sense, but not sure. :confused:
     
  2. Magnification ratios for macro lenses compare the size of the object being photographed to the size of it's image that is projected onto the film or sensor plane. By that definition, the magnification doesn't change regardless of what camera the lens is used on. Small-sensor compact cameras can do great close-up shots without needing to have high magnification ratios because the sensor size is so much smaller than the final viewing medium (screen or print) and the physical image on the sensor has to be magnified further to view it.

    A Micro 4/3 camera is only seeing and recording the central portion of the image circle of your lens, so the lens will appear to have a higher magnification for the same reason as I described above for compact cameras.
     
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  3. BarefootPilgrim

    BarefootPilgrim Mu-43 Top Veteran

    517
    Dec 23, 2009
    Westchester, IL
    Bob
    The simple answer (as Nic said) is no it doesn't and no it won't. It's important to remember that the size of the sensor does not change the physics of the lens. A 100mm lens is still a 100mm lens. A 2:1 macro is still a 2:1 macro.

    The thought that's leading you astray is "which effectively doubles the length." But that's not what happens...

    The lens still produces the same size image that it would produce on its originally-intended 35mm full frame film camera. But your 4/3 sensor only sees the center of that image. What actually happens is the 4/3 sensor crops the lens's image before the camera saves it to memory card.

    Another way to think of it is this: Shoot an image on film with the Pentax Spotmatic for which this lens was originally made. Process the film, stick it in your enlarger and blow it up to whatever size you please. But before you print it, crop out 50% of the image, leaving only the center.

    That's what your 4/3 sensor does. Thinking of it as "effectively doubling the length of the lens" is inaccurate and will lead you down the wrong road. This becomes so confusing because most of the experienced folks who should know better find it more convenient to talk about "effective focal length" of 4/3 and APS-C camera/lens combinations, when instead they should be talking about crop factors.

    Cropping a photo is not the same as doubling the focal length of the lens. Hope this helps improve your understanding at least little.
     
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  4. songs2001

    songs2001 Mu-43 Top Veteran

    693
    Jul 8, 2011
    Ignore the posts above. Just consider it a 1:1. Even Olympus puts equivalent macro on their marketing material.
     
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  5. Sammyboy

    Sammyboy m43 Pro

    Oct 26, 2010
    Steeler Country
    Here's the spec's. for the SMC Pentax-M 100/4 Macro lens. You will notice max. magnification for the lens is 1:2 (1/2 life size) and not 2:1 which would indicate twice the actual size.
    Also attached is a hand held photo taken with my M5 + Nikon 60mm/2.8 AFD Macro lens set at 1:1 magnification (life size). This photo shows and measures the long side of the m43 sensor set at 4:3 aspect ratio.
    As you can clearly see, the crop factor has nothing to do with magnification, the image only takes up more real estate on small sensors.
    As for the Pentax lens, it should be a lot of fun to use.



    Lens Mount: Pentax K.
    Optics: 5 elements in 3 groups. Pentax Super Multi-Coated.
    Diaphragm: 6 blades, stops down to f/32. Full, and sometimes half-stop clicks.
    Filter Thread: 49mm.
    Close Focus: 1.48 feet (0.45m).
    Maximum Reproduction Ratio: 1:2.
    Size: 2.54" diameter x 3.05 " long (64.6 x 77.5mm), rated, when focused at infinity.
    Weight: 12.4775 oz. (353.75g), measured. 12.70 oz. (360g), rated.


     
  6. Ned

    Ned Mu-43 Legend

    Jul 18, 2010
    Alberta, Canada
    You get a "more closely cropped image" on a smaller sensor. I think that should make more sense than what macro magnification ratios "really" mean, lol.

    The apparent magnification won't be any more than APS-C though, which is a 1.6x crop. Full Frame is a much wider aspect ratio (3:2) than Four-Thirds (4:3) so saying the image looks "twice as big" is also misleading because the 2x "Equivalent Focal Length" is measured from the diagonal which is going to be greatly increased by the extra width of Full Frame and APS-C sensors.

    Take this bee for example. If a Full Frame shot looks like this:
    sensor-size_comparison.
    Then an APS-C sensor would capture the crop like this:
    sensor-size_aps-c.
    And a Four-Thirds crop would look like this:
    sensor-size_four-thirds.

    See what I mean?
     
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  7. getoutandshoot

    getoutandshoot Mu-43 Regular

    80
    Apr 28, 2012
    A magnification ratio of 1:2 means the size of image as measured on the sensor (or film) is 1/2 life size. For example, a tiny flower that measures 4mm wide would be captured on 2mm of the sensor. This will remain true regardless of the size of the sensor or the "cropping factor" of the camera format. So *technically* no, putting a 1:2 macro lens on a m4/3 camera does not make it 1:1. However, *practically*, you cannot ignore the cropping factor. Your m4/3 camera really is cropping the image that would have been captured on the native film/full frame sensor. And of course this really does "zoom you in further," assuming the lens and the smaller sensor are able to capture all the detail that is there.

    I'm just saying some of the same stuff that others said above (including songs2001), in my own way.
     
  8. chicks

    chicks Mu-43 Top Veteran

    876
    Feb 1, 2012
    The Big Valley, CA
    So, *technically* it's a dumb question, since I got the macro formula backwards. :rolleyes:

    Thanks for all the great responses, time to take this "new" lens out for some *practical* shootin'. ;)
     
  9. ~tc~

    ~tc~ Mu-43 Hall of Famer

    Oct 22, 2010
    Houston, TX
    Ignore this post because it is flat wrong.

    A 1:1 lens will project an image of a 1" object as 1" on the sensor. Obviously, if your sensor is only 1/2" wide, you're not going to "see" the entire 1". When the image is blown up to the same size as one from a larger sensor (assuming the same pixel density in today's digital world), it will appear to have higher magnification, but that is all coming in the "blowing up", not the lens/capture.
     
  10. Ned

    Ned Mu-43 Legend

    Jul 18, 2010
    Alberta, Canada
    No Songs post was not wrong, you have merely misinterpreted it. Most people don't care what 1:1 means in a technical sense. They care about how the IMAGE will be AFFECTED. That "blowing up" you speak of is the affect that will be seen on the magnification of the image.

    Do we really need to confuse people by telling them that the 1:1 ratio doesn't change because the capture of the lens hasn't changed, only the canvas which it projects onto? Does anybody really care about that? People want to know how close they can "zoom in" on the image before they lose focus, and how closely they can detail their shots.

    I don't use "Equivalent Focal Length" because I don't need it. I've used Four-Thirds and other systems long enough that I'm comfortable with knowing for myself what one focal length and magnification ratio does on each system. Plus, as I described in my post above... I think it's silly to convert focal length using the diagonal on two systems with completely different aspect ratios. It works with the numbers, but doesn't work with the images... Who cares about numbers? It's the affect on the image that this conversion is supposed to tell us. The photos may show that there's no difference in apparent magnification between APS-C and Four-Thirds, but there is still a CLEAR difference between either APS-C/Four-Thirds and Full Frame.

    However, to tell somebody that they are flat wrong for using an Equivalent Focal Length to make themselves comfortable in knowing the difference between what will be captured by their camera, is also wrong.

    Simply put "Equivalent Focal Length" is not a technical value. It doesn't need to have some sort of obscure technical meaning. It's just a figure that helps people calculate in their head that "this image will look kinda similar to an image taken with this other camera using this other lens". Not very technical, is that? As I've shown with images, it's also not accurate at all for our system (though it would be for APS-C or other 3:2 formats). So stop calling it wrong or right, it's neither. It's a made up value, but it does have meaning to some.

    Granted, in a lot of ways I wish Equivalent Focal Length didn't exist. It's supposed to simplify matters, but instead it makes us post these long threads to sort out and define what it really means.
     
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  11. ckrueger

    ckrueger Mu-43 Veteran

    304
    Jul 16, 2011
    Ned photo illustration is all you need to know. It's obvious from the photo that lens magnification does not increase, but the photo is more tightly cropped making it appear that it is.

    What we really need to do is speak in terms of mm of subject coverage. A 1:1 lens on a 5D covers 36mm, but a 1:1 lens on an EM5 covers 17mm. A 1:2 lens on an EM5 covers 35mm.
     
  12. songs2001

    songs2001 Mu-43 Top Veteran

    693
    Jul 8, 2011
    It's not wrong, it's equivalent to 1:1, what you see on the back of a LCD in a 1:2 lens in a M43 camera will look like a 1:1 lens when used in a 35 mm.

    This language is used on every M43 product regarding macro.
     
  13. Crdome

    Crdome Mu-43 Hall of Famer

    Sep 11, 2011
    West Central Indiana
    Chrome
    Ned,

    Am I correct this shows the Four Thirds crop and not the even smaller Micro 4/3 crop?

    You get a "more closely cropped image" on a smaller sensor. I think that should make more sense than what macro magnification ratios "really" mean, lol.

    The apparent magnification won't be any more than APS-C though, which is a 1.6x crop. Full Frame is a much wider aspect ratio (3:2) than Four-Thirds (4:3) so saying the image looks "twice as big" is also misleading because the 2x "Equivalent Focal Length" is measured from the diagonal which is going to be greatly increased by the extra width of Full Frame and APS-C sensors.

    Take this bee for example. If a Full Frame shot looks like this:
    sensor-size_comparison.
     
  14. flash

    flash Mu-43 Hall of Famer

    Apr 29, 2010
    1 hour from Sydney Australia.
    Gordon
    4/3 and micro 4/3 use an identical sensor size.

    Gordon
     
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  15. Amin Sabet

    Amin Sabet Administrator

    Apr 10, 2009
    Boston, MA (USA)
    Yes, but that doesn't make it right.

    Imagine if you had four 16MP MFT sensors stuck together, made one big 64MP sensor out of them (similar to a 64MP 135 format sensor), and had a lens which could both provide 1X (1:1) magnification and outresolve that sensor. Imaging you use it to take a flower picture at 1X.

    Now say you take that same lens and put it on a 16MP MFT camera and shoot it at 1X. You would get half of that flower (linearly) on the sensor with the same amount of detail captured per unit of the sensor.

    Now if you made a same size print from both cameras, the MFT print would show a greater image magnification than the 64MP camera print. It would look like you got more of the tiny details. However, if you cropped the 64MP file to the central 16MP and printed that at the same size as the MFT print, they would look exactly the same. More importantly, blew up the images and tried to point out the detail of a tiny hair on the flower, there would be no difference in your ability with one camera vs the other.

    Calling a 1:2 macro lens "equivalent to 1:1" on MFT is exactly the same as cropping out the middle 25% of a 1:1 MFT shot and saying that the lens is now "equivalent to 2:1". It's analogous to "digital zoom".
     
  16. songs2001

    songs2001 Mu-43 Top Veteran

    693
    Jul 8, 2011
    M43 is same crop as Four Thirds. Equivalence was most useful with optical finders.

    With EVF and digital cropping, it's less useful.
     
  17. Sammyboy

    Sammyboy m43 Pro

    Oct 26, 2010
    Steeler Country
    Did you look at the photo I posted. It was taken at 1:1 magnification (life size), of a ruler, it shows the length of the long side of 4/3 sensor. In this case it shows 31/32" or 16.7mm. The usable dimension on the long side of the sensor is 17.3mm, this indicates that the lens is very,very slightly more than 1:1, or most likely my inability to hold the camera true at this magnification. What ever the case may be, it shows that crop factor has nothing to do with magnification. Forget all the spin and buzz words you may hear, it's pure B.S.
    Anyone with a macro lens can perform this test for themselves, and I certainly urge them to do so, maybe there wont be so much misinformation floating around.
     
  18. songs2001

    songs2001 Mu-43 Top Veteran

    693
    Jul 8, 2011
    That's what equivalence is. A crop. It's literally every where. Even exif info has equivalent focal length. For real everyday use. Knowing that 100 1:2 is like a 200 1:1 on 35 is the only thing you need to know.

    Unless you have a better way.
     
  19. songs2001

    songs2001 Mu-43 Top Veteran

    693
    Jul 8, 2011
    Take that same lens, take the same pic with a 5d and then one with the ep3. Print the pics at 300 DPI. Which ruler is bigger? The pic taken with the ep3. That's all you need to know. The ep3 ruler should be around 2x longer. But like Ned pointed out, it's different depending on which crop you use.
     
  20. Sammyboy

    Sammyboy m43 Pro

    Oct 26, 2010
    Steeler Country
    You can print it to the size of a billboard, that has ABSOLUTELY NOTHING to do with lens magnification, no matter how you spin it.
    If I took a photo of a worm 1cm long at 1:1 magnification on an 8x10 camera, the worm would measure 1cm long on the film. If I took a photo of a worm 1cm long at 1:1 magnification on an 35mm camera, the worm would still measure 1cm long on the film. This has nothing to do with printing, viewing on a computer, a TV or a iPhone.
    You are getting off the subject of lens magnification when you try to intervene with printing or viewing distance.
    Again, forget crop factor and the buzz words, 1:1 magnification doesn't change from format to format. Try it your self.
     
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