Backfocus ?

[majormorgan]

Hiya,

I hear this term kicking around for people to watch their 'backfocus'.

Are they referring to focusing on the ground glass in a 35mm adaptor [e.g the HVX focusing on the ground glass] or are we talking about something I need to get checked on my HVX regularly to do with internal mechannics?

Many thanks in advance,
Richard
MajorM.

 

[Orangemoon]

You are correct...it's a 35mm adapter issue (Or, Varicam, etc.). If there is a backfocus issue with the stock HVX, it's something inside the plastic and best left to the pros at the service department.

 

[Barry_Green]

Backfocus comes into play when you use interchangeable lenses.

A lens is designed to project an image onto a surface (usually the CCDs or CMOS sensors; in the case of a 35mm adapter you'd be looking at projecting the image onto the ground glass). The distance from the lens elements to that surface needs to be precisely collimated.

When using a zoom lens on a removable-lens camera, what can happen is that if the back-focus is misadjusted, then when you focus on an image at one focal length (say, full telephoto) and then change to another focal length (say, wide angle) the image will go out of focus. When your backfocus is properly adjusted the image will stay in sharp focus at all focal lengths.

 

[majormorgan]

Great, thanks to you both for explaining it in depth for me.

Should mean that my focusing is looking great front and back as the images look really sharpe.

Thanks again !

Richard M.
MajorM.