Originally posted by BretW At the same time, my wife studied frogs in the rain forests of Madagascar, and I was lucky enough to tag along with her.
You'll have to have a look at this
frog shot done with the Pentax FA 43/1.9 Limited then...
This lens is not a macro and it isn't weather sealed either. But it belongs to a number of special lenses Pentax have in their arsenal.
When there is a deal (such as
Cyber Monday), it is rather affordable as well ($566), considering that it is a full metal lens.
Originally posted by BretW And after adapting to high ISO shooting in rain forest this summer, it became clear that we probably wanted a full frame body--a bigger sensor is like a bigger lens, right?
Actually it isn't.
A larger sensor has more dynamic range, but does not provide better low-light capabilities.
Full frame shines in low-light when you use bigger (brighter) lenses that are not available for APS-C cameras.
For instance, the equivalent of a 50/1.4 lens on FF for APS-C would be a 33/0.9 lens. This lens does not exist. Even when it is physically possible to make a lens for APS-C it would normally be a lot more expensive then the FF equivalent. You can read more about this subject in the
"Low noise benefit of FF vs APS-C equals ... zero" thread.
A very remarkable exception is the Sigma 18-35/1.8. It is equivalent to a 27-53/2.7 lens on FF but does not cost an arm and a leg. It is exceptionally good as well, so if you can get lenses like this, you do not need to regret not having an FF sensor for a second. Unless, of course, you'd like the same zoom range (27-53) with an even wider aperture than f/2.7.
Originally posted by BretW Pentax certainly has cheaper high end glass.
Yes, however, it is worth waiting for these Black Friday and Cyber Monday deals. You'll then get the Pentax lenses at the old prices before an executive decision was made to force all dealers to ask the same price (-> MAP policy).
Originally posted by BretW 2) Pentax is already a bit sparse on the variety of good glass, and that problem gets even worse when one is limited to WR lenses.
Don't forget excellent third-party offerings from Sigma, Tamron, Samyang, etc. though.
In particular Sigma complements the Pentax offering very well and they have some excellent lenses. Some of the most modern ones are weather-sealed as well.
Originally posted by BretW With the camera in hand, I do already feel some twinge of regret over the small sensor (using the 18-135 kit lens, which is all I have so far).
There are advantages to an FF sensor and I'm a fan myself, but in many shooting scenarios your APS-C sensor will do just as fine. The Sony sensors Pentax is using have such low noise that you can push them quite a bit and hence rival the dynamic range of some older FF cameras. You could check that out at the
DxOMark sensor ranking, but I'd just enjoy my K-3, if I were you.
Originally posted by BretW My hope is that sensor sensitivity continues to improve, and that investing in good Pentax WR glass now pays off with future bodies that are better in low light.
The Sony sensors are already pretty spectacular. Unless there is some drastic technology change (such as micro prisms that allow ditching colour filters), you won't see a dramatic decrease of noise levels. Backlit sensors are a bit more sensitive, but apparently it is very expensive to manufacture them at larger sizes.
The Pentax community is quite optimistic about an FF model appearing in late 2014, but remember that will only help you if you are prepared to invest into the big, bright glass that is necessary to create a low-light advantage.
Originally posted by BretW 2) I have always wanted lenses with fully uncoated glass for tropical forest work, so that fungus would be a non-issue. Just as a thought experiment, how would uncoated versions of high end lenses perform? How much benefit is really in those organic coatings?
Coatings are very important in order to increase the t-stop (how transmissive the lens is for light) and for dealing with flare/glare.
You can get some old manual focus lenses with single layer coatings (or perhaps even with no coating at all) and check for yourself. Rather than using an uncoated lens, I'd rather get a couple of cheap SMC lenses and then either clean or discard them, should they develop fungus.