Originally posted by nanok no. please, perspective depends _only_ on distance to subject, not on lens, not on format or alignment of planets. lens specific distorsions are not part of perspective (they are part of optical aberrations
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You are right, I meant FOV.
Originally posted by nanok i wouldn't bet on that. this has been the case so far, but keep in mind much larger sensors are notoriously bad at higher iso's (medium format).
In any case, there is one other thing to consider. Fullframe cameras are not released as often as APS-C models. So typically, APS-C cameras will have more recent sensors in them, which may close the gap. I think that's why the K-5 managed such a high score at DXOmark.com when it was first tested.
Originally posted by nanok no. the ratio of light gathering between each "well known" apertures is 1/2, that's precisely why they are well known, and if you want to verify, you need to square them:
5.6^2/4^2
1.96000000000000000000
we're mixing units here. 1.5x crop is a linear measurement, light gathering capabilities are a factor of surface (so linear squared, one might say, except squaring the crop factor is inaccurate unless you're talking about a rectangular frame). in short, assuming the same aspect ratio, the "35mm" sensor is twice the surface of aps-c, and this is why it's usually "one f-stop away" in nearly everything (like dof at same field of view). this is also why f-numbers need to be squared to obtain the exposure ratio (they are a linear ratio between focal length and aperture size)
I know. Though a crop factor of 1.5 would result in a surface area 2.25x smaller than fullframe, instead of 2x. But yes, I am talking about a rectangular frame. I have yet to see a camera with a sensor shaped unlike a rectangle.
Originally posted by nanok dof: no, as you see from above, it's pretty much the same (close enough it makes no difference)
comparing noise performance of ff at iso200 to aps-c at iso100 on modern sensors is a purely academic exercises imho.
For ISO 100 and 200 I might agree. But I don't like running my K-5 any higher than ISO 4000. With a comparable fullframe sensor I could go to ISO 8000.
Originally posted by nanok all these "all else being equal" comparisons have two problems: all else is never equal, and comparative discussions might not be meaningful for practical purposes from a point on (for instance, comparing the output of a sensor like the one in the k-5 with one in a "comparable" 35mm camera, using good quality (read: excellent) glass, one might be surprised how close they will be). Technology is at a point where one no longer _needs_ bigger sensors for image quality purposes (exceptions are rare, and tend to drift towards phaseone and the likes anyhow), you might _want_ it for a bigger, brighter viewfinder, you might dream of it because you have some special pixie dust lens which only really works "properly" on a 35mm frame, or just because you can afford it. but need it? nope. sensor technology has reached "maturity" a few years ago (about the time k-5 was released), in other words. that's not to say improvements are no longer possible, but rather that you probbaly don't need them
now i should run...
ps: sorry for the rant, nothing personal, i have a compulsive reaction to misuse of the term "perspective" in particular
No problem. I have a compulsive reaction to misuse of the term "speed" for a lens.
And btw, I am perfectly happy with my APS-C based system. I do acknowledge the fact that e.g. a Canon 70-200/4 would be near the same size as my 50-135/2.8, have the same FOV on fullframe, etc. But a 6D is bigger than my K-5. As I like to travel, I like to keep things small and light.
[on-topic] (at last
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As for the mighty K-3, I may buy it, or I may not. It depends, really. I do want a better autofocus system, but from what I've heard, the K-5 II already is an improvement where I want it. When the K-3 comes out, no doubt will there be a lot of people selling their K-5 II's. So I will just see if the price and specs on the K-3 are enough to make me buy it instead of such a used K-5 II. I do hope they are though.