Originally posted by badlydrawnboy ... I prefer shooting with primes, and my budget is about $750.
My main use of the camera will be photographing my child (due to be born in three months), although I also enjoy taking pictures when I travel. Street/urban/landscape is also an interest, but the reality is I don't have abundant time for that now so those would be the third priority.
I've narrowed it down to the following list: 21, 40, 43, 70, 77. I'm not sure whether to go with a wide angle and a med tele (i.e. 21 & 70/77), a wide angle & long normal/short tele (21 & 40/43) or a long normal/short tele & med tele (40/43 & 70/77).
Part of the problem is I'm not very familiar with the 40/43 effective focal length, and not sure where those lenses "fit in". I'd definitely appreciate the extra stop of light on the 43 & 77, but I think if I had one of them it could be my low light lens and I could go with the cheaper alternative for the other focal length.
Standard disclaimer: Nobody can tell you what you're going to like.
That said, the effective focal length of the 40/43 lenses is, um, 40 and 43mm respectively. If by "effective" you mean, what's the field of view? the answer is that the K10D's sensor provides a so-called crop factor of 1.5x -- or to put it more precisely, a narrowing of the field of view of about 33%. In other words, with a 40mm lens, you'll be getting a field of view similar to what you'd get with a 60mm lens on a 35mm film SLR. In short, somewhere around 35-40mm is very close to "normal" human vision and thus a very nice focal length for candids when you're reasonably close to your subjects.
Me personally, I would not START with a 21mm prime and a 77mm prime. That would mean I would have nothing but a wide and a telephoto lens -- nothing in the normal range, where a good 50% of my shooting occurs. I don't own either the 40 or the 43 but people here give very good reports on both of them. The 43 appears to be more expensive and is a bit faster. The pancake form-factor of the 40mm lens appeals to some folks. Personally, I think it looks a bit like a sawed-off shotgun, but I hear that both lenses take wonderful photos.
You didn't mention the FA 50 f/1.4, not sure why. It's also a very nice lens, and fast. If I could only have ONE lens on my K10D, and if I was forced to make that lens a prime, well, I think I'd either go with the 43 or the 50.
You said you prefer shooting with primes. You didn't say why. It it's just because your standards are really high and you'd rather miss shots than have them less than perfect, well, I admire your dedication to perfection, I guess. If you just like primes because you like primes, perhaps because you don't like think about zooming, well, that's fair enough, too. On the other hand, if you picked up an anti-zoom-lens prejudice in the past shooting with film cameras, you might want to reconsider. There are some very nice zoom lenses available now, thanks to major advances in the technology for making zoom lenses work with digital cameras. The Tamron 28-75 f/2.8 is one of my favorite lenses. Quality is very good throughout and, well, it's a heck of a lot more versatile than any prime. Alternatively, there's the Pentax 16-45 f/4, which is an outstanding lens.
I tend these days to think of prime lenses as specialists. I wish I had more primes, I really do. But even if I did, I'd only pull 'em out when I know in advance exactly what the shoot really requires. I will also note that, the fewer lens changes I have to make, the fewer opportunities there are to get dust on the sensor. That was not such a problem in the film days as it is now, which is one reason why it's lucky for us all that zoom lenses these days are so much better than they used to be.
If I have a minute or two tomorrow, I'll try to take some comparative shots with my FA 50 and the Tamron 28-75, setting the Tamron to 50mm and setting both lenses to something neutral like f/5.6 or f/8. I'll be interested to see the results myself.
Will