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I found that with some lenses the mirror fails to reset when the shutter is released, it fails on my 50mm F1.7 AE but works on my 50mm F1.4 AE. the focus confirm adapters don't appear to support F1.7 anyway. It works with a Yashica ML 35mm F2.8, and the ML 200mm F4. but fails with the DSB 28mm F2.8.