I still am not entirely sure what you are asking. I'm sorry that I can't figure it out. Someone else please jump in...
How about setting subject distance overrides with macro?
...
I need to verify whether setting subject distance made any different.
No. Not if it was lower than what the lens can focus at. I mean, OK look at it this way ... It's got very little to do with overrides and more to do with the optics. Most of these tiny pocket-sized PowerShots use a technology called "annular folded optics". It lets them cram a fairly useful zoom (usually around 3.2x max) into a tiny, tiny protrusion. The downside is they have a narrow focus range. This is compounded by the fact most of the SD cams don't have an aperture, in the traditional sense.
If you set focus to macro, and zoom out fully, the nearest object you'll be able to focus on is 30mm away. So if you override focus and set it to it's lowest setting, nothing is going to be in focus closer than 30mm. Not possible. It is a physical limitation. There's no "trick" or anything that CHDK can pull off. (maybe if you had a supplemental lens...)
Now, say you zoom fully telephoto. That's 3x optical zoom, but now, because the way the lens elements are positioned, you won't be getting anything in focus in
ten times the distance above, or 300mm. Again, you can set the focus to any override under that, but it won't help anything. It's a physical limitation.
Digital Zoom is like resizing a small picture in a paint program. It gets resampled, it's interpolation. The bad part being that this is approximation based on surrounding pixels, so the more you "zoom" the less sharp your image will be. However if you lower the resolution of your image, this also provides "digital zooming" without the image degradation. Does that make sense?
I shot with iso of 10
No. Sorry.
It's not really ISO 10. For these cameras lowering ISO does nothing. While you can force it to
display ISOs lower than 80, if you do an ISO bracketing test, you'll notice both in the histogram and in the noise pattern when zoomed in ~800% in your favourite image editor, that there is zero difference between images shot at any ISO < 80 and images at ISO 80. The sensor in these cameras are already maxxed out. I mean it's staggering that Canon is pulling 8.3 million pixels off a tiny 5.75mm x 4.31mm CCD... I'm quite surprised that ISO 80 is relatively clean.
You can test this yourself, the steps are outlined on the
Camera Features Chart - ISO Tests wiki page.
I hope this is answering some of your questions.
