Macro Lens Question

Discussion in 'Beyond the Basics' started by PhilGarber, Aug 19, 2009.

  1. PhilGarber

    PhilGarber TPF Noob!

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    Hi-

    I'm in the market for a macro lens and I have a question about the minimum focusing distance. I'm looking at the Canon 2.8, 100mm Macro but I see it's minimum focusing distance is 1 foot. Does this mean the mini distance to auto focus the lens or even manual focusing? If this is true of just auto focusing, I'm not worried. I've heard that with macro photography you don't really want to use the auto focus much anyway (right?). However, if this is true of manual focusing the lens also, what's the closest-focusing macro lens I can find?

    Thanks,

    Phil,
     
  2. Big Mike

    Big Mike I am Big, I am Mike Staff Member Supporting Member

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    The minimum focus distance is physically, the closest the camera/lens can be to the subject and still focus...it doesn't matter if it's auto or manual.

    12 inches is actually pretty close for a focal length of 100mm.
     
  3. PhilGarber

    PhilGarber TPF Noob!

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    Thanks Mike! That was helpful. I think I'll be saving up then ;). Have you been posting less, or have I just not seen you as much?
     
  4. Garbz

    Garbz No longer a newbie, moving up!

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    A note on macros, the closest focus distance is a function of angle of view and reproduction ratio. A 60mm 1:1 macro will have a much closer focus distance than a 100mm 1:1 macro, but when all is said and done they are both 1:1, the latter often preferred because getting closer physically to achieve the same reproduction ratio is likely to spook the tiny subject.
     
  5. Big Mike

    Big Mike I am Big, I am Mike Staff Member Supporting Member

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    Even I get to take some vacation time here and there. ;)
     
  6. DigitalScape

    DigitalScape TPF Noob!

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    Another option to reduce the minimum focal distance is the use of extension tubes. The tube reduces the minimum focal distance (at the expense of infinity focusing -- for macro images, this is usually not an issue).
     
  7. Murray Pastko

    Murray Pastko TPF Noob!

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    The minimum focusing distance is measured to the sensor, not the front of the lens. Murray
     
  8. PhilGarber

    PhilGarber TPF Noob!

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    Thanks man. I didn't think of that.
     
  9. PhilGarber

    PhilGarber TPF Noob!

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    Haha, you definitely deserve a vacation:biggrin:.
     
  10. JerryPH

    JerryPH No longer a newbie, moving up!

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    You also further reduce the DOF and quality with most of them.
     
  11. Big Mike

    Big Mike I am Big, I am Mike Staff Member Supporting Member

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    Does an extension tube really reduce quality?
    I can see it introducing a little more CA but it certainly won't hurt as much as using diopter 'close up' filters.
     
  12. Overread

    Overread has a hat around here somewhere Staff Member Supporting Member

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    It will vary, dending on the amount of tubing you add and the quality of the diopter (closeup filter) that you are comparing it to.

    Using tubes alone will cause some image degradation since you're moving the lense away from its optimal position - however outside of controled studio test shots this image degradation is for most cases not noticable and will have little effect on the usabilty of images and other factors such as user error, lighting shifts, subject movement, camera shake and others will have a far bigger effect on images.

    As for in comparison to the diopters its certainly better than the cheap ones, but some are harder to beat. I know some macro shooters (Far better than me) who consider the Raynox DCR250 to have equal image quality to that of using tubes for similar magnifcations.


    For any setup as you increase the magnifaction factor the depth of field is going to get smaller also your going to get a darker and darker viewfinder image as well for focusing (as well as increased demands on lighting the scene as well for taking the shot).
    Personally when using a dedicated macro lens I prefer using teleconverters over extension tubes since the teleconverters will not change the focusing distances of the lens (it retains infinity focus and also retains its minimum focusing distance) but all your magnifications get increased - so in effect for around 1:1 magnification you get an increased working distance (note that with a teleconverter the notes on the focus for magnifcation ratios will no longer be correct).
    The Canon 100mm won't work with official canon teleconverters, but I belive that it will work with some 3rd party ones, but I am not sure as to which
     

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