def mtf_ts_extractor(mtf, freqs):
    """Extract the T and S MTF from a PSF object.

    Parameters
    ----------
    mtf : `MTF`
        MTF object
    freqs : iterable
        set of frequencies to extract

    Returns
    -------
    tan : `numpy.ndarray`
        array of tangential MTF values
    sag : `numpy.ndarray`
        array of sagittal MTF values

    """
    tan = mtf.exact_tan(freqs)
    sag = mtf.exact_sag(freqs)
    return tan, sag
