All Figures

	Figure 1: Our J-band mosaic image of IC 348, showing a field with a square-root intensity scale. The eight BDs (objects with spectral types M 6.5) identified by Luhman (1999) are marked by boxes. The large circle marks the cluster area.
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In the text

	Figure 2: Histogram of J-band magnitudes for the central 6' radius area in our IC 348 cluster image (thick solid line) compared to the histogram for the background fields (dotted line, scaled to the same area as the cluster region).
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In the text

	Figure 3: JLF of IC 348, computed by subtracting the background model histogram from the cluster area histogram. The error bars represent the uncertainties caused by the photometric errors ( mag) and the Poisson statistical uncertainties of the background subtraction.
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In the text

	Figure 4: The IC 348 JLF (histogram) compared to a model based on the Kroupa (2002) field IMF (dashed line), the stellar part of the Kroupa (2002) field IMF (solid line), the Chabrier (2002) log-norm IMF (dashed-dotted line), and our log-norm IMF fit (dotted line).
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In the text

	Figure 5: The IC 348 JLF (histogram) compared to the two marginally acceptable Kroupa IMF like models with maximum BD population. The solid line shows the model with the power-law slope in the sub-stellar part (model "Fit I''), the dashed line shows the model "Fit II'', in which the change of the power-law slope occurs at .
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In the text

	Figure 6: The IC 348 JLF (histogram) compared to the IMF models for IC 348 derived by Lada et al. (1998); the model L1 is shown by the dashed line, model L2 by the dotted line. The solid line shows the model based on the IMF suggested by Luhman et al. (2000) for IC 348.
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In the text

	Figure 7: The IC 348 JLF (histogram) compared to three models for the IMF in the Orion Trapezium Cluster. The dotted line shows the model by Hillenbrand & Carpenter (2000), the dashed line shows the model by Luhman et al. (2000), and the dashed-dotted line the model by Muench et al. (2002).
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In the text

Figure 8: Illustration of some of the IMFs used in this paper. All distributions are normalized to give the same number of objects in the range. The thick solid line shows the Kroupa (2002) field star IMF, the sub-stellar part of which is shown by the thick dotted line. The thick dashed-dotted line shows the IMF "maximum BD fit I'', the thick dashed line shows the IMF "maximum BD fit II''. The solid parabolic line show the lognormal fit IMF, the dotted parabolic line represent the Chabrier (2002) field IMF. The thin solid line shows the Trapezium cluster IMF as derived by Muench et al. (2002), while the thin dashed line shows the Trapezium cluster IMF as derived by Hillenbrand & Carpenter (2000).

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In the text