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Forum: Pentax DSLR Discussion
05-17-2009, 11:47 PM
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I'd assume the reason is that AF sensors as small as the actual red dots would be close to useless - way to often they'd be on an object without any edges or contrast. the bigger the sensor, the more likely they'll hit on something. Too big and they're hard to control. So a compromise has to be reached. That's my guess, anyhow.
BTW, regarding the nosie issue: I've looked at enough images from the K100D, K200D, and K20D to be convicned there really isn't that much differences in noise performance in any of them. So much affects the amount and appearance of noise in a shot - the color of the light, the exposure, the dynamic range of the scene, whether the subject is in the lights or the shadows or the midtones, the detail in the scene, etc. And of cours,e viewing 100% is unfair to the camera with more pixels. It's really tough to make apples-apples comparisons, but when you do, differences are usually in the you-have-to-pixel-peed-to-see-them category, and even then, you end up with half the viewers picking one as better and half the viewers picking the other.
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Forum: Pentax DSLR Discussion
05-15-2009, 06:37 PM
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I'd say there is a very clear difference between the pics, but it sure as heck looks lens/focus related, not sensor related.
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Forum: Pentax DSLR Discussion
05-15-2009, 12:46 PM
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That's what it looks like the me - the book furthest in front looks more in focus than the rest. All it would have taken was one other book a little further in front, or a plant with a leaf overhanging the shelf - within range of your selected AF point, of course - to get this effect. But it's easier to remove focus issues from the equation completely using the angle method than to try to *fix* them.
Why not? If text doesn't do it for you, try something else. The point is to remove any possibility of focus issue from the sharpness tests.
Yeah, but ACR has to have been individually tweaked to demosaic those very different RAW files, and even with all user-controllable settings the same, you have no way of controlling what is going on under the hood. Again, the goal is to remove all *possible* variables. If you see the same with all other RAW converters, only then can you be *sure* it isn't just a case of ACR doing better with one camera than the other.
Then I'm missing something. They look like the same FOV. Straight crops of the same dimensions from sensors of different resolutions should show entirely different FOV. Unless maybe you shot from different distances to make the crops look similar? In which case, you've just introduced another variable you need to eliminate.
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Forum: Pentax DSLR Discussion
05-15-2009, 11:41 AM
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So maybe the camera focused on a different part of the bookshelf than you wanted. That's certainly common enough, and pretty much unavoidable.
The real test would be to shoot a subejct where *something* is guaranteed to be in focus. Like newspaper on an angle. Find the sharpest area of the K100D and comapre it to the sharpest area of the K20D photo.
Also, the difference you are seeing could potentially be in the ACR's profile for the two cameras - would be interesting to see hwo the camera JPEG's compare, or the RAW files as processed by PPL or some other program.
BTW, you mention using the remote release - but are you also using the timer to get MLU? Might as well remove that variable form the equation too.
Oh - I'd also check to seeing if PS provides different options for the resizing, and try them out. There *are* different algorithms that can be used, and they vary in their effectiveness. Also, when downsizing images, it is common to want to apply some degree of sharpening. Another interesting test would be to *upsize* the K100D image to match the K20D.
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