Trap Focus for D300

Hi !!!

Anyone who can explain it step by step starting from reset options ... !?

See page 271 in your Owner's Manual under "a5, AF Activation". Set it to "AF-ON Only" and the shutter button's

half-press will be disabled and you use the AF-ON button to focus.

Dunno 'bout the D300 specifically but the usual method for trap focus is as Joe described it.

Assign autofocus to AF-ON only, not the shutter release button.

Prefocus on the desired zone or distance.

Press shutter release and wait.

Depending on your camera there are other tricks. For example, with the D2H's built-in intervalometer, I can set it to check conditions at predetermined intervals and if there is a subject within the focus trap zone, it will take a photo. Frankly, it's an awkward and mostly unsatisfactory method. After the timer expires I'm out of luck. If I set the timer to extend the maximum useful period, I'm stuck with a limited number of samples. If an object enters the trap zone between samples, no photo.

Some older 35mm SLRs from over a decade ago, such as a Pentax model, had a far superior system. It could be set to trigger the camera whenever an object entered the focus trap zone. I'm disappointed that Nikon's high end pro dSLRs don't have this built in. It shouldn't be necessary to use any additional device or tricks.

Personally, I find trap focus AF useful with the D2H only with handheld macrophotography. I prefocus on the desired zone and the shutter trips only when the desired area is in perfect focus. But this works only with AF or AF-S lenses, so I can't use it with my 55/3.5 Micro Nikkor.