Magnification, aperture, sharpness and diffraction - a test with the MPE 65mm macro

Discussion in 'Photography Equipment & Products' started by Overread, Feb 4, 2010.

  1. Overread

    Overread has a hat around here somewhere Staff Member Supporting Member

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    A little test I did with the new lens

    Setup:
    Camera and lens:
    Canon 400D
    Remote cable release
    Canon MPE65mm macro
    Teleconverter used for last tests - Sigma 2*teleconverter
    Hoodman anglefinder - set to 2.5* magnification to aid focusing

    Lighting:
    Canon 580EX2
    Offcamera flash cord
    Lumiquest softbox

    Support:
    Manfrotto 055XPROB tripod
    Manfrotto Junior geared head
    Ebay focusing rail (single section) (note apparently also the same as the Adorama focusing rail)

    Subject setup:
    Single 2 pence UK coin
    Single LED bulb torch with flexi arm

    Camera settings used for each shot:
    1/200sec shutter speed
    ISO 100
    Aperture (varies)
    Manual flash power output (varies)



    The full setup:

    Camera and lens mounted using the lenses tripod collar (sold with the lens) onto the focusing rail; the rail being attached to the quick release plate of the geared head and the whole setup mounted on the tripod. The geared head was set to an angle (as shown on its head markings) of just over 45 degrees - this tilted angle was delibate as I wished to know the performance of the focusing rail whilst at a tilted angle with the whole setup. In addition a tilted angle lets the varying depths of field be displayed on the coins. Due to limitations in gear the flash had to be handheld by the photographer.

    Each shot was focused by using the LED torch as a point of bright light, the light shining onto the coin surface. This proved to be essential at the greater magnifications as the image through the viewfinder would become very dark, coupled with a very small depth of field this further increases the difficulty of accurate focusing. The 2.5* setting on the Hoodman angle finder proved to be very beneficial for the aid of focusing at such fine magnifiations - though those with liveview can use up to 10* magnifcation on the preview image for even further fine focusing.
    Focusing for each setting was achived by moving the focsing rail and not adjusting the focus on the camera, for this purpose in the tests. In this the focusing rail performed very well, allowing easy movement of the rail whilst the pressure screw was applied and not requiring any tightening further once the hand is removed from the rail controls. In the field further finer focusing could be done by adjusting the focus on the lens itself, unless preserving a fixed magnification was needed.
    Test shots were taken and the flash power adjusted accordingly based on the output of the camera histogram - note that this along with the handholding of the flash itself did lead to some inconsistant results - especailly where the angle of the flash changed between shots. AT this small distances even small changes in the flash distance and angle could lead to larger changes in the resulting image. To counter this a better test would be to have the flash mounted on a fixed stand

    Once each series of shots was taken the magnification was adjusted to the next level (as written on the lens barrel) and the focusing rail repositioned to aquire the new focus.

    Test shots were then uploaded to the computer and the RAWs were processed - however only the white balance was adjusted for these shots (and the brightness on a very few). Even when output as JPEGs the sharpness, contrast and other settings have not been adjusted from the cameras base settings. This results in a softer image than would be possible by using tools such as the clarity slider in RAW processing and the unsharpen mask in the final stages of image editing = however it gives a level field that all the shots can be viewed on, rather than show up slight differences in the amount of sharpening applied (since whilst the amounts could be fixed each shot would have required different amounts in normal processing). In addition the major dustspots were also removed (least I think I got most of the major ones). More minor dustspots which would normally be removed from proper images were left in.

    To view the fullsized versions of each shot please follow the links below each example shown here - you really do need to see the larger versions of many of these since downsizing for posting on the forum will hide away a lot of the loss of sharpness in the shots. Note again that these are fullsized links and not 100% crops so they might take some time to load.

    The complete set on flickr:
    http://www.flickr.com/photos/24534478@N04/sets/72157623350445656/detail/

    1:1 (life size) - true macro magnification - this is where the subject is the same size in real life as it appears on the image sensor in the camera body. It is the generally agreed point at which macro photography begins.

    Aperture at f8
    [​IMG]
    http://farm5.static.flickr.com/4009/4329833751_7a4c409b2e_o.jpg

    Aperture at f10
    [​IMG]
    http://farm5.static.flickr.com/4031/4329838143_89aa4a66b7_o.jpg

    Aperture at f13
    [​IMG]
    http://farm3.static.flickr.com/2713/4330577054_423ae6a2fc_o.jpg

    Aperture at f16
    [​IMG]
    http://farm3.static.flickr.com/2514/4329848621_66a52c4eb2_o.jpg


    2:1 - twice life size magnification - the subject is the twice its size on the camera sensor as it is in real life

    Aperture at f8
    [​IMG]
    http://farm3.static.flickr.com/2761/4330597698_124e0c9b99_o.jpg

    Aperture at f10
    [​IMG]
    http://farm5.static.flickr.com/4058/4330603406_9258c4f7b5_o.jpg

    Aperture at f13
    [​IMG]
    http://farm3.static.flickr.com/2694/4329853811_502f3b9f86_o.jpg

    Aperture at f16
    [​IMG]
    http://farm5.static.flickr.com/4047/4330592598_fb642d514d_o.jpg


    3:1 - twice life size magnification - the subject is the three times its size on the camera sensor as it is in real life

    Aperture at f8
    [​IMG]
    http://farm3.static.flickr.com/2681/4329874787_7b6fdac336_o.jpg

    Aperture at f10
    [​IMG]
    http://farm3.static.flickr.com/2762/4329879301_45dcb9e7db_o.jpg

    Aperture at f13
    [​IMG]
    http://farm5.static.flickr.com/4010/4330616982_fe74e2a6c5_o.jpg

    Aperture at f16
    [​IMG]
    http://farm3.static.flickr.com/2746/4329887633_7a412428c9_o.jpg


    4:1 - twice life size magnification - the subject is the four times its size on the camera sensor as it is in real life

    Aperture at f8
    [​IMG]
    http://farm5.static.flickr.com/4004/4329891251_22888a2de0_o.jpg

    Aperture at f10
    [​IMG]
    http://farm5.static.flickr.com/4010/4330628408_e9c15259a5_o.jpg

    Aperture at f13
    [​IMG]
    http://farm5.static.flickr.com/4052/4329899431_e415d53dce_o.jpg

    Aperture at f16
    [​IMG]
    http://farm5.static.flickr.com/4054/4330637642_c2df8bea2b_o.jpg


    5:1 - twice life size magnification - the subject is the five times its size on the camera sensor as it is in real life. This is the maximum magnification that the MPE 65mm macro is capable of without further modification to the setup

    Aperture at f5.6
    [​IMG]
    http://farm5.static.flickr.com/4006/4329917049_8d2dc77172_o.jpg

    Aperture at f8
    [​IMG]
    http://farm5.static.flickr.com/4071/4329920909_d496c9d101_o.jpg

    Aperture at f10
    [​IMG]
    http://farm3.static.flickr.com/2769/4329910787_2a54b26e51_o.jpg

    Aperture at f13
    [​IMG]
    http://farm5.static.flickr.com/4028/4330641132_a5d875de7b_o.jpg

    Aperture at f16
    [​IMG]
    http://farm3.static.flickr.com/2748/4329914113_3f214edc4c_o.jpg


    And for fun:
    10:1 the subject is the ten times its size on the camera sensor as it is in real life. This is the result of using a 2*teleconverter with the MPE macro lens

    Aperture at f8
    [​IMG]
    http://farm3.static.flickr.com/2704/4330662450_27983df899_o.jpg

    Aperture at f13
    [​IMG]
    http://farm5.static.flickr.com/4031/4329924857_5848215a3f_o.jpg


    Test results:

    As you can see the effect of the increase in magnification leads to a softening of the results from the lens; further whilst closing down the aperture continues to give the greater depths of field at these increased magnifications; the effect of diffraction softening the final resulting image grows more noticable as magifiations increase. This means that aperture selection cannot simply be forgotten about as the magnifiaction of the shot grows.



    1:1

    Here we can see that f8 is clearly the sharpest aperture to use of those tested. However results from both f10 and f13 show little difference between each other and would still be very usable when sharpened in editing. The results from f16 however are showing a far more noticable effect of diffraction (espeacially when compared to the f8 results)

    2:1

    Here we can see that things have got harder still, f13 is now more comparable to that of f16 from before. F10 is fairly usable still however, whilst f8 remains the sharpest aperture from those displayed.

    3:1

    f16 is now becoming a very soft aperture to use indeed and f13 is quickly following it. f10 would be the highest suitable aperture at this magnification now. Also note how dustspots are becoming far more of a problem in these shots (remember only major spots were removed the rest remain)

    4:1

    f10 might just be usable, but its really softened a lot since the smaller magnifications. In all honestly f8 would be the new ideal aperture to use for this magnifcation.

    5:1

    The first thing to notice is that f5.6 has appeared on the scale now, this is in responce to the constant softening of results and whereby f8 might no longer remain the most suitable aperture to use. Secondly looking at the results its clear that whilst f16 gives a massive depth of field for this range the results are very soft indeed. Even opening all the way up to f8 we still have a very noticably soft image - f5.6 might be the most desirable aperture for this magnification - even though it makes things a lot harder with its far finer depth of field.

    10:1

    Ok not as strict a test here since lower apertures are missing, but still at this high magnification one might be more forced to pick the smaller f8 over f5.6 just because of the improvement in depth of field that the aperture brings.


    Test improvements:
    select a single point on the coin to be the point of focus for all the shots.A left and bottom line on the image would also allow easier compartive results in the difference of subject area shown at each different magnification. Further a fixed flash position would have allowed for more consistant results with the flash head to have been recorded - lessening differences in sharpness due to contrast changes.
     
    Last edited: Feb 4, 2010
  2. Montana

    Montana TPF Noob!

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    Wow! Nice write up and samples! Interesting. That is one heck of a lens.
     
  3. Overread

    Overread has a hat around here somewhere Staff Member Supporting Member

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    It certainly is, tricky and I can see why tripods are prefered, though even the short working distance is infact a bonus with this lens (gives one more chance to be leaning on or crouching on the ground and thus reducing shake) there is even the lefthand brace technique where one holds the stem/object that the subject is on with the left hand and then rest the lens atop the arm.

    Also I made this up quickly for those wanting an easier summary:
    magnification - best aperture to use

    1:1 f13
    2:1 f13
    3:1 f10
    4:1 f8
    5:1 f5.6 however in practice f8 might be a more workable aperture due to the small depths of field

    remembering of course that this is all based on a Canon 400D and that other camera models might give different performance results.
     

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