[OM] Re: Digital decisions

Subject: [OM] Re: Digital decisions
From: Wayne S <om4t@xxxxxxxx>
Date: Wed, 08 Mar 2006 11:43:06 -0500
At 09:12 PM 3/7/2006, Joel wrote:
>I'm curious, Wayne (and I know we've discussed your issues with the
>E-1 before), do you remember your AF settings?  I was using a KatzEye
>screen at the time and set the focus point for center only.  I
>experienced no AF weirdness except when I pointed the lens into the
>void.  Also I was using the DZ 50-200 exclusively.  Perhaps a tele
>grabs on better.

I believe the AF issue is what Ag-en referred to, that the firmware update
change the AF sensor sample rate by slowing it a bit and hence put it into
a range that aliases with incandescent lamps on dimmers. It would
go wild. I also tried attaching an FL-40 flash to use the auto-focus
assist light and it also had problems. I did not have auto-focus points
specifically selected. I know I checked it for dust per recommendation
by Olympus:

"We value you as an Olympus customer and appreciate the opportunity to assist 
you. "
"Although we have three dust collection areas larger pieces of lint/dust can be 
moved from the SSWF or from mirror slap into the AF sensor area and cause 
malfunction or poor AF operation. You might want to take a look in your camera, 
the AF sensor is located just below the mirror. If you see dust we would 
suggest sending the camera to us for a cleaning."

I checked for dust, none. The AF works great in all other lighting. 
The fact that the assist light did not help furthers my believe that the pulsing
rate of the lights on dimmers over-whelmed the sensor. The camera is
no longer in my possession so I cannot do any more testing. You can try
though, set some ambient light on low with a dimmer control and test AF.
I was using the 14-54 lens. I would suspect that selecting a single sensor
would only make a difference if that also affected the sample rate.

Now that you mention it, I also received this response:

"One other very important setting that will save a lot of time and 
heartache,"Focus Point Selection". Do you use single point autofocus or auto. 
If you use "Auto" focus point selection the camera needs to search for the 
closest subject within the three focus points. In low light or if the subject 
is moving from one point to another it can easily confuse the camera. What 
autofocus point selection are you using?"

"It is very important to use the AF illuminator in low light. TTL contrast 
detection needs a certain amount of light to focus properly. It is necessary to 
use the AF illuminator assist function in low light for the camera to focus 
properly without searching."


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