Back focus ring : Anybody cares to explain?

[andybiz_2005]

I have a DVX102AE (PAL) version of the camera & I read somewhere about adjusting the back focus with a focus chart & the instructions goes like this :

Before starting, mount your camera on a tripod and adjust your camera's viewfinder to achieve sharp focus.

Ideally, you should place our free test pattern chart at least 25 Metres from the camera (If you can't place the chart 25 metres away just position it as far away as possible).

Set the iris to manual

Set the zoom to manual

Open the iris to its widest aperture - If the illumination on the test chart is too bright for the open iris, reduce the light or move the chart to a darker area

Zoom fully into the centre of the chart (maximum focal length of the lens)

Focus on the chart

Zoom out fully

Loosen the back focus ring retaining screw

Adjust the back focus ring for the sharpest focus

Repeat steps 4 through 8 until focus is sharp throughout the zoom range

Tighten the back focus ring retaining screw to secure the ring

Note: Most lenses are at their sharpest focus between f4 and f8

I'm curious to know if my DVX102AE has a back focus ring & if I need to use a focus chart to adjust the focus on my DVX? Is it neccesary, or not neccesary to adjust the back focus as the DVX already has auto focus settings? Thank you all for your advice.

Andrew

 

[mikkowilson]

No need for BF on the DVX.

Back focus can only be agjust on removable lenses (not the XL series)
It is used to focus the back of the lens to the sensors in the camera. This is only necesary when mounting different lenses to different cameras.
With hard mounted lenses the distance is fixed and therefore the lense was built focused to the sensors at the factory with no need for adjustment.

- Mikko

 

[andybiz_2005]

Hi Mikko,

Thanks for clearing up my doubts on what BF really is. Because during a previous shooting assignment, I observed another cameraman adjusting back focus on the production company's Sony digiBetacam. So I thought it was applicable for mine too.