OK I'm still waiting for my D200. Not that aren't available its just the tax man ripped out half my savings so I'm not there yet.
I keep hearing that the D200 will show up any flaws in poor quality glass. But I have no idea what this means to me, the average user. Will my 18-70DX, 70-210F4, and tamron 90mm macro give poor results on this camera? Or are they refering to lenses like a sigma 28-80 old standard kit lens? Would I only be happy with my results if i used 70-200VR and 17-55DX? If so then I'm better off with my D70 (but I LOVE that viewfinder).
Ah and just what does that mean? Big purple fringing? Soft images? Any clarification welcome.
I'm nearly done. Only one more shot. Just give me five minutes...
Here's an analogy that demonstrates the situation.
You have a modest little subcompact sedan. If you put bargain basement tires on the car it's no big deal because it will get you from point A to point B just fine.
You have a Lotus sports car. If you put bargain basement tires on the Lotus it won't go around corners any faster that the subcompact sedan.
So poor glass is glass that gets in the way of the camera. Some lens are inherently soft and produce photographs with inferior color. If you have a camera with good color rendition and a large sensor (like the D200) these lenses will hold the camera back.
Some kit lens like the 18-70 will give decent pictures so I personally wouldn't call them poor glass but if you are trying to sell your photographs to somebody expecting the highest quality images then that 17-55 class lens will probably be more likely to deliver it. So poor glass is also relative to your particular needs and expectations.
Each person has their own requirements. With the DX format, I found the 24-85 3.5-4.5 to be equal with the 20mm prime at f8 and smaller. On the other hand, the 17-35 is sharp at f4 at 24mm. The 70-200 is impressive at f2.8 135mm.
Quite honestly IMO the lenses you have will fit your purpose if you are happy with the results you are getting now. Due to the better sensor in the D200 and the higher MP the camera will show up any flaws in your technique especially camera shake. You may find that you have to work harder on your technique with the D200 as the D70 is more forgiving,however the D200 has more settings which can make photo taking easier as you have mentioned one the larger viewfinder. Even with the most exoensive glass available rubbish photo`s can be taken with poor technique.
Trying to keep it simple some lenses which work well on 24x36 do not work as well on DX.
One of the issues is the micro lenses on the sensor surface do not perform well with light at a low angle - primarily a wide angle issue which is why Nikon introduced wide angle DX lenses.
Digital sensors record R, G and B separately so if they are slightly out of register at the sensor surface it is more of an optical issue with digital than film. The main categories of lenses likely to have this issue are older wide angles and pre IF long lenses.
Next digital increases mid tone contrast and sharpens it - provided the lens is good enough to resolve it to what is needed by a 10 or 12 MP sensor. Whilst I have not tested it I expect the $100 28-80 "kit lens" for 24x36 would struggle with digital at A3.
If you never print bigger than 6x4 with digital the lens is not important. If you print A3 some lenses that do it well with film may not do it as well with digital.
Photography is a bit like archery. A technically better camera, lens or arrow may not hit the target as often as it could if the photographer or archer does not practice enough.
>I keep hearing that the D200 will show up any flaws in poor >quality glass. But I have no idea what this means to me, >the average user. Will my 18-70DX, 70-210F4, and tamron >90mm macro give poor results on this camera?
Those lenses you listed above are good and will be fine on a D200. Don't get stressed about it. Are their sharper ones?.... Yes but they also cost a ton more money and what you have is good too.
If your Tamron SP 90 macro gives poor results on ANY camera, that's an indication that we've gone too far. It's optically one of the best lenses out there.
I frankly don't think many of us have seen bad glass. We've seen some glass that's definitely not as good as some others. Here's an example of BAD glass. These two are not take at the same time - they are about a week apart, so don't hold the lighting against either lens.
The one on the left was taken with the Tamron SP 500mm/f8 mirror lens. The one on the right was taken with a Vivitar 500mm/f8 mirror lens, one of the ones that is often seen on the big auction site for around $90. I'm on record here at Nikonians claiming that the Vivitar is "not even a lens" it's so bad, but here's the evidence. The Tamron was hand-held, but the Vivitar was taken from a very solid tripod, using a cable release (but no mirror lockup). The focus points are slightly different, but actually that's not much of a matter as there really isn't anything in the Vivitar image that's sharp enough to call "in focus."
The images are straight-from-the-camera JPEGs, default everything from a D100.