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step up ring - 49mm filter

Discussion in 'Olympus Cameras' started by tr7dan, Apr 14, 2011.

  1. tr7dan

    tr7dan New to Mu-43

    Apr 14, 2011
    Does anyone know if there are any problems with using a 37 - 49 step up ring on my epl2 with kit lens and then a 49mm polarising filter (from my om days)


  2. Robert Spoecker

    Robert Spoecker Mu-43 Regular

    Jan 23, 2010
    Step up rings should be no problem as long as you are going from a small lens to a larger filter. Vignetting only occurs when you go from a large lens to a small filter.

    Don't forget that the camera may not auto focus properly using a regular polarizer. You should always use circular polarizers on digital cameras.
  3. mauve

    mauve Mu-43 All-Pro

    Mar 9, 2010
    Paris, France
    Only when the camera relies on phase detection, which is not the case of :43: cameras. Contrast detection do work with linear polarizers.

  4. Should be no problems other than a bit of extra size and weight. Going from a 37mm to a 49mm filter almost doubles your glass area and therefore weight, but if the kit 14-42 MkII zoom for the E-PL2 is internal focusing the extra weight is not being driven by the focus motor as it would be on a 14-42 MkI.
  5. tr7dan

    tr7dan New to Mu-43

    Apr 14, 2011
    OK, thanks for that.

    I have a sackful of 49mm filters from my film camera days - is it normal to use red, yellow and orange filters for monochrome pics on a digital camera in the same way I used to use 'em with FP4 or are the pictures taken in colour then converted on the laptop? If so, how do I put tone in the sky etc.?

    I can't quite get my head round how it works.


  6. mauve

    mauve Mu-43 All-Pro

    Mar 9, 2010
    Paris, France
    The beauty of digital is, you can try and see what works and what doesn't without losing money on film processing. So, the best you can do is make some tests (and report results here, we're always eager to learn too).

    Now, how does it work ? In a pinch, a sensor is a greyscale device that's basically color blind. On top of it is glued a matrix of colored micro-filters in 2x2 repeating pattern Red-Green/Green-Blue.

    Each pixel of the sensor therefore records the intensity of the light's wavelength corresponding to its "personal" filter. A computing algorithm (quite complex) is needed to recreate a true color image out of that matrix.

    A simpler process (for explanation purpose only) that would create a color image would be for instance :

    (upper case characters denote true recorded value, lower case characters are used to describe value copied from neighbor pixel) :

    RG¹ -> (Rg¹b)(rG¹b)
    G²B -> (rG²b)(rg²B)

    Repeat ad lib until you have iterated through each group of 4 pixels.

    This naive process would lead to an image having 1/4th of the pixel count of the sensor, but pixels 4 time bigger than the physical ones.

    To get back to your question, I don't think it would be wise to add another colored filter on top of the Bayer matrix I've described. But you can simulate a color filter directly in the monochrome mode of an Olympus pen camera, if you rely on the out-of-camera jpeg. If you prefer post processing from a raw, you'll need to de-matrix the image in color first, and then convert it to b&w.


    ps. for historical record, there's been only one digital black and white camera ever released to the general public, the Kodak DCS 760M (http://www.luminous-landscape.com/reviews/cameras/kodak-760m.shtml) - without bayer matrix nor anti-aliasing filter, this kind of camera would be the perfect machine for b&w photography even today, but the market is so small there's little chance we'll see one again. But I'd kill for a strictly b&w E-Pen.
  7. Pan Korop

    Pan Korop Mu-43 Veteran

    Mar 31, 2011
    Phare Ouest
    If you're comfy with it, go ahead: it will work the same, or about. Benefit: you'll get the effect straight from the out-of-camera .jpg.

    Now, many of us kept only the Pol-filter, for the Y, YG, R (etc.) routines can be post-processed AND fine-tuned by choosing the right mix of R, G, B channels to get the desired B&W.

    It was a pain to find, process, Ortho film, for old-fashion portraits or just to keep foggy landscapes foggy. Or dig out the old deep blue Wratten filter. Now the right mix of G+B channels in Photoshop do it with more comfort and a right to error ;) 

    PS: agreed with all above, notably Mauve's.
    I believe, too, that having experience with the trad' filters will help you greatly in the digital lab: you already know what you want, instead of trying halfhazardly.
  8. I prefer to have an original colour image that is neutral and then make any changes and effects I might want during post-processing.
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