Now i understand, why noone was interrested in having a bigger range of aperture lol.
Can someone tell me, how i can get the lower limit in DOF in a script, and how the Autofocus works in the A590???
The built-in DoF calculator/display is your friend -- instructions
on the wiki. No clue about getting the value within scripts (you could program in the calculation from scratch, although it might be slow due to uBasic's 10 ms/command limitation).
if you wish to find the upper _hardware_ ISO limit, you'll have to compare RAW images.
Thanks! I'll try this and report back -- this probably explains the apparent smoothing-out of the JPEG histogram. Although in all honesty, the noise at ISO1600 is so extreme that higher sensitivities probably won't be worth it, but would be nice to know simply for curiosity's sake.
There's a very serious and misleading error in the calculator at that cambridgecolor website. The author doesn't know much about optics. The diffraction limit is also determined by the physical diameter of the optics used to create it. It can't be calculated from the f-ratio alone. For example an 8-inch diameter lens at f-5.0 creates a much smaller airy disk than a 2-inch diameter lens at f-5.0. Basic optics. Every telescope maker knows this. This is why they build larger telescopes. The larger the telescope, the smaller the airy disk, the finer the details that can be resolved.
Everything I've seen is based off of the computation that
Airy Disk Diameter = 1.22 * wavelength * f-number (i.e. 2.6, 4.0, 8.0, etc)
I know that it can also be expressed in terms of subtended angles and angular resolution, but only ran the first calculation, and it agreed reasonably with Cambridge In Color. If this is indeed in error, could you please post the correct calculation, or assist me in doing so? I really don't think I'll get a good result if I grab my Modern Physics textbook and try to derive from first principles. Thank you in advance!
Even if the author does correctly include the lens diameter in his calculator, he'll still be in error. It is also determined by how perfectly curved the glass is.
That makes sense... none of the calculations are perfect, so we're making a set of simplifying assumptions (IE approximating the size of the Airy disk, etc). Can't we use rough approximations to give an upper limit on resolving power based on diffraction? We won't ever get results that good in real-life, but at least it'll make clear what the physical limitations are.
