Originally posted by FHPhotographer I
Is there "too much" lens for some sensors?
Not in the sense of actually producing worse results than a lesser lens - just in the sense of not actually demonstrating its superiority.
Simple example: consider viewing thumbnails only. No way could you tell the difference between any two lenses looking at a picture the size of a postage stamp. View the images at typical web dimensions (say, 400x600) and maybe you could tell the very worst lenses from the very best, but most would basically look the same, somewhere in the middle. View at 100% and then you can see everything there is to see.
Quote: too much lens for a 6mp , but ok for a K10, and best on a K20?
In the sense described above. A 6MP camera might not have enough resolution show the difference between two given lenses, just as is the case when viewing thumbnails. Move up to a 10MP sensor and some difference become more apparent, just as viewing at web dimensions might. Move up to 14MP and maybe now it's more like viewing the images at 100%.
Quote: I realize that a K20 is going to bring more detail at the same size to an image than a K100 will, but how does the lens figure into that.
If the lens is not *capable* of that kind of detail, more pixels won't help. Tape a Coke bottle to your camera instead of a lens and see if the K20D gets you any more resolution than the K10D. More pixels will display more details only if your lens is capable of produing details that your current sensor is not showing because it lacks the pixels. Which is to say, if it is outresolving the sensor in the sense we talking about.
Actually, in practice, it's probably never that simple - it's not like resolution is constant across the frame, or the same at all apertures or subject distances. But conceptually, that should help clarify things.
Quote: By "too much" I mean is the cost of that lens not justified because the output images won't benefit from the lens' ultimate resolving power, e.g. a 31mm on a K100D?
There can easily reasons other than resolution why a lens might be worth it. If you're going to shoot at f/8 all the time, the 31 might not beat the kit lens at all in resolution on a K100D in the center. It might beat the kit lens in the corners, though. And it will beat it more and more in resolution as you go to wider apertures. But if it also has better color, contrast, bokeh, or whatever else, that's going to hold regardless of whether it is outresolving the sensor or not.