You'd think I would have picked up on this, long ago, but I didn't. Maybe it's because I'm still in film, and only think about digital, as the next step I will take some time in the future. However, it has smacked me in the face, in the last few days. I like to take scenic shots of landscapes. My 24mm f2.8 AIS is my "wide" lens and a 35mm f2 is my normal. I got a 28-105mm, recently, and it worked out very well too. Let's say I go to a Nikon DSLR. That 24mm is now a 36mm. That's workable as a landscape lens, but it loses quite a bit of FoV. So, I need a 24mm equivalent for a DX sensor type body. That puts it at about 16mm, if my math is right. That drops me right into the odd end of optics where perspective can get weird and distortion is common. Of course, this is easily fixed with Photoshop, which I can get for $300. Of course, the price is $500 for a third party lens in this range, and right up in the 4 figures for a Nikon. All of this, just to get back to a basic 24mm FoV. I think that lens was about $100. Have I missed anything ?