On 09-12-20 15:47 , Ofnuts wrote:
On 20/12/2009 20:34, LOL! wrote:
On Sun, 20 Dec 2009 10:00:02 -0500, Alan Browne
wrote:

On 09-12-20 4:00 , Wilba wrote:
The Canon EF 50mm f/1.8 II "Nifty Fifty" has a reputation for two
shortcomings, 1) softness at wide apertures (OK from f/2.8), and 2)
erratic
focus under difficult conditions (low light, shallow DOF).

Many people claim that 2) is a result of the crudeness of the cheap
focussing motor and electronics in the lens, that those components
are not
able to provide the required accuracy and control of motion of the
focus
ring.

But I wonder if 2) is actually a result of 1) - if the AF sensors
have fuzzy
images to work with, how /could/ the system nail the focus in difficult
conditions?

It would be interesting to see what happens when the AF sensors have
sharper
images to work with (e.g. at f/2.8 or f/4), but my 450D refuses to
AF when
the DOF preview button is pressed, so I can't test that. External
aperture
perhaps?

Any ideas for how these competing hypotheses could be tested? Is
there a
consequence of either hypothesis that could be disproved empirically?

Offhand, even if it is soft wide open, the AF should settle on the
"sharpest" slightly soft contrast, which on average should be sharp
enough.

Could you post a simple target wide open?

In fact could you post the one on p18 of this document, shot at a 45 deg
angle. I'd like to compare it to the Minolta 50 f/1.7.

http://focustestchart.com/chart.html#ActualChart


Munching popcorn, watching the usenet comedy show, while I enjoy
using my
slightly slower but highly accurate contrast-detection focusing cameras.
Just what any intelligent person wants, phase-detection focusing that
focuses slightly faster but never accurately. All those shots, missed
forever.

too ****in' funny

This is such good free entertainment. Beats all the comedy routines on
TV.

/me wonders if they ever realize what gigantic fools they continually
make
of themselves daily ...

It just so happens that DSLR users are a bit more concerned about focus
than P&S users because:

1) they get to choose which part of the frame is in focus

2) out-of-focus parts aren't obscured by sensor noise or
diffraction-induced blur.

We also like high SNR - in this NG. So it's best not to reply to the
brainless automaton aka the P&S troll.