John Glover
Veteran Member
Ian is correct in his assessment, at least as far as my 6900 is concerned. There was a lot of griping and complaining about the poor low light performance, and to soem degree it was true. But in my experiences, it has not been a serious issue, no more so than with my 35mm gear. My 6900 autofocuses at a 3 sec, f/2.8, ISO100 exposure fairly consistently, provided I follow the guidance that Ian has spelled out below.
Another key point to try, is to make sure you get the AF target centered on the contrasting edge you are trying to lock on to. The 6900 only has a simpler center AF point, but I believe the 602 has a wide area setting? For a low light shot, I'd switch this off and activate only the central sensor. This will reduce the area in which the AF system has to deal with and should improve your chances of getting a good lock. Once a good AF is achieved, then lock it in, either with a hlf press of the shutter or shut off the AF, then recompose and shoot. Maybe this will help.
Also, I agree with Ian that a change in the ISO should not affect the AF. All the increase in ISO do is to effectively increase the gain across the CCD. The AF system is looking for contrast and phase detection. A change in the ISO should not change this, as the AF is surveying the ambient scene's contrast, while the ISO bump up only affects the metering system.
And, in any event, this has become a very interesting thread, and has stayed quite civil too! Kudos to all who have particpated so far!!
John
Fuji 6900Z, Fuji2600Z,
Pentax PZ-1p, Pentax ZX-M, Pentax MX, Oly Stylus
http://www.pbase.com/jglover
Another key point to try, is to make sure you get the AF target centered on the contrasting edge you are trying to lock on to. The 6900 only has a simpler center AF point, but I believe the 602 has a wide area setting? For a low light shot, I'd switch this off and activate only the central sensor. This will reduce the area in which the AF system has to deal with and should improve your chances of getting a good lock. Once a good AF is achieved, then lock it in, either with a hlf press of the shutter or shut off the AF, then recompose and shoot. Maybe this will help.
Also, I agree with Ian that a change in the ISO should not affect the AF. All the increase in ISO do is to effectively increase the gain across the CCD. The AF system is looking for contrast and phase detection. A change in the ISO should not change this, as the AF is surveying the ambient scene's contrast, while the ISO bump up only affects the metering system.
And, in any event, this has become a very interesting thread, and has stayed quite civil too! Kudos to all who have particpated so far!!
--
John
Fuji 6900Z, Fuji2600Z,
Pentax PZ-1p, Pentax ZX-M, Pentax MX, Oly Stylus
http://www.pbase.com/jglover
)))))