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

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    Overread
    Overread  63768 forum posts England18 Constructive Critique Points
    4 Feb 2010 - 6:04 PM

    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.

    Link to the image set on flickr - the title of each image denotes the aperture used and the magnification factor of the shot. Note that fullsized versions of each shot are availible for review

    Test results - after a quick review of the presented images at fullsize (you know its quicker to view them on flickr than it is to wait for windows image viewer....)
    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.

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    4 Feb 2010 - 6:04 PM

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    User_Removed
    4 Feb 2010 - 6:29 PM

    Very good!!

    (Puts on a very bad Clint Eastwood accent...)

    You have to ask yerself this question...

    Will the results sell...???

    Wink

    Smile

    Last Modified By User_Removed at 4 Feb 2010 - 6:31 PM
    Overread
    Overread  63768 forum posts England18 Constructive Critique Points
    4 Feb 2010 - 8:17 PM

    hmm anyone got an old coin collection that they want to see - really up close?? Wink

    montechoro
    montechoro  112340 forum posts United Kingdom2 Constructive Critique Points
    4 Feb 2010 - 8:33 PM


    Quote: Hmm anyone got an old coin collection that they want to see - really up close??

    I've got an old farthing and a sixpence somewhere!

    Great detail and results overread - thanks for the technical info

    Last Modified By montechoro at 4 Feb 2010 - 8:33 PM
    lawbert
    lawbert  71713 forum posts England15 Constructive Critique Points
    5 Feb 2010 - 5:06 PM

    So you decided on the monster magnification of the MPE65mm Alex.
    A good Choice and an excellent test write up and images, very informative and interesting.
    I done a similar test on coins when I got the 100mm f2.8l is but without the detailed write up!!
    Enjoy your new purchase and lets hope for some warmer weather soon to awake the creepy crawlies.
    All the Best
    Paul

    Overread
    Overread  63768 forum posts England18 Constructive Critique Points
    5 Feb 2010 - 5:58 PM

    Oddly I never really tested my other macro lenses in the same way - mostly just stick to f13 and shot away and since results were mostly good enough I never questioned. Infact I probably wouldn't have tested the MPE in this way save that I caught sight of a thread in the MPE group on flickr where members were discussing the differing settings they used at various magnifications and I was surprised to see very wide apertures sneaking in at the 4 and 5 times marks - so I did the test myself to see the effects.

    I've now got to test the 70mm and 150mm against the MPE at 1:1 and see how things line up Smile

    glsammy
    glsammy  8195 forum posts United Kingdom1 Constructive Critique Points
    6 Feb 2010 - 7:18 PM

    Your test result pretty well match with what I've found using that lens.
    My general rule is 1:1 F16. 2:1 F13. 3:1 F10. 4:1 F8. 5:1 F5.6 would be best but just to give a half chance of a bit more depth I use F6.3.

    Maybe F16 isn't "best" for 1:1, but I've had very acceptable results with it.
    link

    Overread
    Overread  63768 forum posts England18 Constructive Critique Points
    11 Feb 2010 - 5:56 PM

    I have been using f6.3 in the last few tests, like you, just for a bit more depth and the overall image quality does not seem that bad. And yes I sometimes reach to f16 but mostly try to stick to f13 at the most - a method of shooting that carries over from my other macro lenses; though I think that the MPE might wear f16 a little better since it seems to be an overall sharper setup at 1:1 (I've got to repeat my test comparison on this at some point)

    glsammy
    glsammy  8195 forum posts United Kingdom1 Constructive Critique Points
    12 Feb 2010 - 8:16 PM

    One point I notice, I've never managed to stack shots successfully when using the MP-e65mm. No doubt that's down to my ignorance and lack of understanding of the stacking software.
    Have you successfully stacked images? The main problem for me is the simple fact the image size varies as you change focus points. Not a problem with my normal macro lens (Sigma 150mm) but a nightmare with the MPe65mm.

    Overread
    Overread  63768 forum posts England18 Constructive Critique Points
    12 Feb 2010 - 8:45 PM

    I have to admit I have not stacked anything with the MPE thus far (any bugs I find are too mobile and early mornings are ... too early - that and itsoften raining in the morning)

    I have used combine ZP and only use the align and do stack commands - though I have also used the do all command whereby it makes a copy of each different stacking version. I do that when I get a series of shots that won't work for some reason and sometimes it saves the stack. Othertimes its a case of trying to find and remove/reorder a missplaced frame or a frame that is throwing the software.

    As for the framing it should not be any problem provided that you ensure that the whole subject that you want covered remains well within the boarders of the image - that way as you zoom in to get the complete layers the subject won't suddenly move outside of the frame area.

    I've also noted that it does not (at least combine ZP) appear to like large areas of the foreground being sharp and then bluring considerably in later shots and bluring over details (like a leg held out in front that might come to blur and cloud over the body behind) though it seems to be a very generalist rule.

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