EM5 digital teleconverter

Discussion in 'Olympus Cameras' started by Gerard, Sep 2, 2015.

  1. Gerard

    Gerard Mu-43 Hall of Famer Subscribing Member

    May 12, 2015
    Vleuten, Utrecht
    Maybe someone can clarify.
    The digital converter of my EM5 magnifies 2 fold, I presume. This presumption is because in the screen a sign is visible of a loupe with '2x' next to it.
    If I put a 2x converter on a lens, I loose 2 stops. However, the magnifying in the camera is a digital proces, not an optical.
    So, I am in doubt, do I loose 2 stops or not.
    My knowledge of digital and/or optical laws is rather limited (in fact it is zero) to construct a logical answer myself.

    Option 1 loosing 2 stops:
    a 100/2.8 with digital converter 'on' becomes a '200'/5.6
    If so, would a 50/1.4 with digital converter 'on', behave the same as a 100/2.8, in terms of sharpness, DOV, etc?


    Option 2 NOT loosing 2 stops:
    a 100/2.8 with digital converter 'on' becomes a '200'/2.8
    If so, keeping in mind that there is no such thing as a free lunch, what would be the downside?
    Last edited: Sep 2, 2015
  2. Klorenzo

    Klorenzo Mu-43 All-Pro

    Mar 10, 2014
    Regarding exposure the answer is no, you do not loose any stop. The digital TC is just a crop+upscale similar to the one you can do in post-processing (but I assume it is based on the RAW file not on a compressed jpeg so it should be better then the one you can do starting from the jpeg). This upscale process "smears" the small details (not much but it's there), IMO a problem only for big prints.

    At the same time if you consider that you used only part of the sensor the answer could be less clear cut when you look at the noise amount so one could say that you are loosing ISO sensitivity. But this is mostly relevant for high ISO shots and if you are after the ultimate IQ that you are not getting anyway with the digital TC.

    Then this magnification process gives you a 2x focal length so the DoF you get should be the same of the corresponding longer lens (at same aperture).
  3. Lcrunyon

    Lcrunyon Mu-43 All-Pro Subscribing Member

    Jun 4, 2014
    You won't lose any ISO sensitivity, because even though you are seeing a x2 crop in the viewfinder, your exposure settings won't change and the digital teleconversion is applied after the image is taken, at the same time any other effects are applied. If you shoot JPEG only, the teleconversion is all you get. If you shoot RAW only, the teleconversion does not get applied to the photo, and all you are really getting is x2 magnification in the viewfinder (which is actually a handy trick for a focusing assist). If you shoot JPEG+RAW, you will get both a full-sized RAW file and a cropped JPEG version.

    There is definitely a loss in resolution with a digitally tele-converted photo. Some folks have posited that it is not as bad as an equivalent crop in post processing, due to algorithms applied in the camera, but I haven't seen anything definitive on this. Noise probably appears more pronounced simply because the image is blown up, but again I am not sure if this is as bad as a normal crop.
    Last edited: Sep 2, 2015
  4. gryphon1911

    gryphon1911 Mu-43 Hall of Famer

    Mar 13, 2014
    Central Ohio, USA
    I've used this feature quite a bit.

    From my findings, you must nail exposure in order for it to be really acceptable. The noise appeared to be more pronounced than cropping in post. I do not think that the algorithm used in camera does a sufficient job.

    In a pinch, it can get you that extra reach, but I'm not sure that most people would be happy with the quality at anything in print bigger than a 4x6.

    As is the case with most things, the best thing to do is to experiment with it and see if it is good enough for your intended application.
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