OK, the previous thread was closed because the conversations went on a tangent. It was understandable due to the strange phenomenon I've discovered about my old Nikkor lenses focus at infinity. I concluded that the focal plane may not be accurately set on mass-produced plastic bodies like the D5100. I decided to perform additional tests and have discovered something even stranger. More on that in a moment.
I would like to add a few more general comments about the D5100 that may hopefully be helpful info.
First, the battery. I don't know how long it will hold up as such, but the battery life on the D5100 is pretty damned good. I bought a second battery as backup, which is never a bad idea, but I had a hard time killing the first battery before I put the second one to work! I also found a $15 third-party charger at Adorama which I recommend, as it's smaller than the Nikon charger, and also brings a car cigarette lighter jack adapter, which can be a handy asset on the road. You can find that here if you're interested: http://www.adorama.com/IBYPT63.html
Next,the multi-point autofocus system can work against you sometimes, typically with objects spatially arranged around each other. Unless there are settings I haven't discovered yet, it's either multi-point or single-point focus. Single-point is handy, but it can be slow and drift about. I wish there was a 4- or 5-point cluster in the center so you could have center-weighted focusing. Don't know if higher-end models have such a feature.
The multi-exposure setting is kinda weird inthat it gives you only two or three multi-exposure options. I guess this is a trade-off they give you on the lower-end cameras, but in the film age even the cheapest FM could multi-expose all day long if you wanted. Even my Fuji S9000 can multi-expose all I want. I know this isn't a big deal, as most people don't use this feature much, but I find the limitation kinda odd.
One last recommendation I'd like to make is that if you're considering buying a D5100 kit, buy the 55-200mmm kit lens as well. While the 18-55mm kit lens is a decent lens, it falls apart at the long end, an example which you can see here:
That's the 18-55mm on the left, the 55-200mm in the middle, and my old 55mm Micro-Nikkor on the right, all shot at F5.6. Pretty scary, right?! I don't think you will regret the additional investment, as it of course gives you a greater imaging range, and I've made plenty of good use of both optics.
Overall however a great camera for the price and highly recommended. Now about those tests I made.
From what I see from my tests,I've concluded that perhaps the issue isn't a miscalibrated focal plane. The best I can deduct is that the sensor arrays are somehow not getting the light rays coming in from the MF lenses correctly. There must be a re-design in the way modern lenses work with CCD and CMOS sensors. The phenomenon is different for different optics, some lenses are just fine, others, like my 20mm F3.5, go off a tangent!
With some exceptions, the lenses can't seem to focus at infinity at the the center of the image area, but come back into focus at the edges. The craziest one is my 20mm. I discovered that going into live view, I was able to focus the center by moving it away from infinity towards the first distance mark at 10ft. This however knocks the edges out of focus! Have a look at this. This is the 18-55mm on the left, the 20mm at infinity in the center, and the 20mm focused via live view on the right:
Pretty nuts, right? The 20mm is focused and actually slightly sharper than the 18-55mm at the edges when focused to infinity. Mind you, these exposures were made at F11, and if you look at the 20mm's depth of field scale:
The lens should be in focus all the way to ~4 ft at infinity at F11!
The 105mm was the next worse offender like this, although nothing like the 20mm.The 20mm is essentially useless on the D5100. The 105mm was essentially focused at F11, but of course the optic's natural diffraction is kicking in by then.
Things are fairly decent with the 55mm Micro-Nikkor as you saw in the example above, but the 18-55mm still has a little better focus in the center, although the 55mm takes it in the edges due to whatever phenomenon is causing the center-edge differentiation. For some unknown reason, my 85mm F2 worked perfectly, as did my 135mm F2.
Assuming I figured my 4shared account correctly, you should be able to download all the full res test images to see for yourself here:
You can compare the kit lenses to the older Nikkors. I made the tests only between F5.6-F16 to have some kind of middle ground between the kit lenses and the primes. There's enough info there however. Also you can see how the kit lenses fare at different Fs. The 55-200mm for instance, handles, and can benefit from smaller apertures before things get ratty. The primes of course can be pushed harder through the F ranges.
So anyway, that's that. I don't really know what to think about it. As I said the best I can deduct is that the RGB arrays are freaking out somehow at the way the MF optics are feeding the light rays. I don't really know what else to think. I had shot a roll of film as well to compare focus against the sensor, but the film, Kodak Portra 160, which is supposedly designed for scanning, turned out to be total garbage. I should have shot Velvia 50, but I made the mistake of believing Kodak's rap that this film was optimized for scanning. :-D It's pure junk.
So if you're curious and have the time, have a look at my tests and tell me what you think. Mind you, these are all infinity tests, simply because I first noticed all this at infinity. I haven't as yet noticed any problems focused closer, but I'm gonna keep an eye out for it. For instance, here's a macro shot I did with the 55mm Micro-Nikkor with a PK-3 ring (right) and a bellows-mounted reversed 20mm (left), both shot on the D5100:
Other than pushing the 20mm to the edge of it's optical universe, they seem fine to me.
So, sorry for the long thread, but I just wanted to comment on my findings. Like I said in my first thread, all this hasn't been a deal breaker for me. I really like the D5100, and at least now I know how and when I can use my old Nikkors with it.