Originally posted by Jonathan Mac The adapters are just hollow tubes so the only way I can imagine that different adapters would affect the blooming in the image is it it were caused by a reflection off one of the internal surfaces of the adapter.
Yes, internal reflections from the adapter are exactly what I found with my cheap imported Chinese adapter when used on the K-1. The inside of the adapter was black, but a very shiny black. Every lens, to a greater or lesser extent, produced a central-image flare or "bloom," as it is termed in this thread. I could pretty much eliminate the flare or bloom with aggressive hooding. However, I could not find appropriate sized hoods, so used a silly looking black construction paper approach, which eliminated the flaring but was unsatisfactory because the "hoods" would not stay fixed on the lens and because they interfered with use of the focus ring and/or zoom ring. (Perhaps it is unnecessary to say that they also did not look very professional and would sometimes even fall off during a shoot.)
What finally did the trick, however, was spray painting the inside of the adapter with black matte non-reflecting paint. I used black RUST-OLEUM Camouflage paint with non-reflecting finish. I got this paint in a 12-ounce spray can from Home Depot at a price of $3.76 plus Ohio sales tax. Now with the matte painted adapter and cheap screw-in hoods (or built-in hoods), the bloom or flare has totally disappeared, no longer a factor.
All this reported experience was with the following A lenses: 45, 55, 75, 120, 150, 200, 45-85, and 80-160.
As for the future, I have the following FA lenses coming later this week: 45, 75, 120, 80-160, and 300/4. I plan to use them on the 645D, also scheduled to arrive this week. As an experimental exercise, I may also try the FA lenses on the K-1 with adapter but without their hoods to see whether the bloom occurs. In addition, I will also need to make a determination whether to keep the four A lenses for which I will have FA replacements for adapted use on K-1 or sell them and just use their corresponding FA lenses as adapted lenses on the K-1. Possibly I will no longer use 645 adapted lenses on the K-1 except perhaps the 120mm macro, which is the best flower macro setup I have found so far. Comments will be appreciated on whether to keep these four A lenses or switch entirely to the FA versions.