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Published online by Cambridge University Press: 14 August 2015
A brief review of extinction effects is followed by a discussion of new Cerro Tololo Schmidt plates. They were exposed on parts of the LMC with filters which reveal the presence or absence of a continuum, such as one scattered on dust, in H ii regions. The results are presented in comparison with the Orion nebula which was observed in the same way. The continuum is always relatively weak in those LMC H ii regions which are significantly larger than Orion, but the continuum averages strong in the Orion-class and point-image nebulae.