Which DSLR Should I Buy?

I am thinking of getting a DSLR. Which one should I buy?

I am looking for something quite cheep because I agree with Ken Rockwell that in most cases more features and pixels in DSLRs do not tend to improve people pictures. He does offer some good suggestions but I need to also consider several other factors:

1. I currently own 2 Nikon lenses. A 50mm 1.8 Prime and a relatively old zoom lens. Both require a motor in the body of the camera for autofocus. (which limits me to a D80 or higher, the D5000 will not work) It may well be better for me to replace these lenses but for now my budget is limited.
2. I don't mind Nikon and Canon but I also appreciate many factors of other companies like Pentax etc. (I also have access to several older Pentax lenses, though they are currently waiting for me in another country)
3. I am interested in used cameras as much as new, such as a used D90 etc.

Any suggestions or useful comments would be really appreciated. 

The image is a Leica S2, the DSLR I want but can not afford. 

Posted via email from Mark Whiting's posterous

Everyone can Function

Another great talk by Randy Pausch, this time on time management. I think everyone should watch this. I think it is pretty inspiring. It is worth the 1.5 hours it takes to watch. 

Hearing but not living advice

I think it is easy to give great advice that people listen to and believe and agree with. However I think it is really rare that they actually manage to implement it. I think this is not because people are not good at implementation I really think it is more because a lot of advice is not designed well for that purpose. Perhaps there is also a proponent that is the kind of person being advised, some people are very willing to document and enable advice as it comes along. However, I think in general people sort of Grok the advice they are given, consciously make some kind of ruling over it. Though I would argue the outcome of that ruling is irrelevant, and then they move on. I guess I think it is more like forgetting than anything else, but in the context of implementing, as opposed to just considering, I think it could be related to a lack of emotive power, of a given piece of advice. 

So I think it is much easier to offer a advice that gives a good potential or ideal solution and much harder to offer advice that will actually get implemented. Maybe this is only the case because a lot of the advice giving I have data on is unpaid design consulting or similar. Perhaps where there is more of a sale there is a greater propensity to follow a given point of suggestion. 

How do you Ask Answerable Questions

I think it is so easy to make design problems that are esentially impossible to act upon. I mean, problems that have requirements that do not take into consideration reality, the issue of course is that it is hard to tell how far something is from reality when it is conceived. I guess sometimes instances like this are considered over ambitious however I think it is actually an issue in many situations where evaluating the complexity of a problem is difficult. For instance in operating systems, the complexity of the systems involved is so high that working out what effect a requirement will have on the rest of the system is really not easy. In some cases, I would say problems like this can be considered wicked however in many cases I think it is not the problem that its self is complex it is the evaluation method that returns data on the problem that is too complicated. For example. The problem of going to the moon is not really that wicked. I mean it involves a lot of complexity and a lot of very high rigour decision making but it is really not a problem that continuously changes and in which any answer is only a very temporary answer. The issue of difficulty in deciding weather the question is answerable is really high. 

Q: Let's go to the moon (can we go to the moon)? 

A: Yes lets, yay (we have no idea if we can or not).

 I wonder, is there a good way to work out early on that a design problem is like this. I think it wastes a lot of time and energy when people persue unsolvable problems. And I really mean is there a way that humans can look on the problem level, not on the implementation level, and establish an informed point of view either way. 

If anybody knows anything about methods for this I would be quite interested. Please comment.