Originally posted by boriscleto Those two lenses are great ideas, and I have them both. The Sigma has everything I'd want in a macro lens: 1:1, an A position, quality, even f2.8. I pretty much stole it on eBay for $60. The Tamron is a little more trouble, requiring an Adaptall PK-A adapter for the A position and a converter for 1:1. It's a great lens otherwise, and also fills in as a moderate telephoto.
For features, I like the KA mount lenses because it makes flash easier, and flash makes macro easier.* Everyone wants 1:1 but keep in mind that the highest magnifications are more difficult. Lens speed looks like a luxury for macro, but adds to flexibility for general use. Faster lenses do mean brighter viewfinders and easier manual focus. I agree with the statement about AF and Raynox, but I've never used either.
I also have a Panagor PMC 90mm f2.8, no A position but 1:1 without adapters. It may be difficult to find. All these lenses are better than my technique; I wish I could blame the lenses but no.
I've used the Cosina (Phoenix version, KA manual focus), the Pentax-M 50mm and 100mm f4s, and the Vivitar Macro focusing Teleconverter. Again, the lenses are better than I am, though the Vivitar MFTC depends on what lens I use. The Cosina feels really cheap and is mostly plastic, but has reasonable optical quality and will last a lot longer than you think. The Pentaxes are the exact opposite in build quality, the 50 is compact, but both are only 1:2 and f4. That means manual focusing is harder, and extension tubes for higher magnification make that worse. The Vivitar is good with a 50mm lens but can cost more than other solutions with all the contacts for KA mount.
*Extension tubes with KA mount contacts are hard to find and expensive. I buy cheap KA 2x teleconverters and remove the glass.