ASK & DISCUSS INDEX

8 years, 2 months ago - John Lubran

Assuming that a variable zoom lens has been properly back focused during attachment to the camera then standard focusing methods ought to work effectively. Zoom all the way to infinity, focus, and then pull back to the frame required, everything should be in focus. Same applies to any other focus distance required. Back focus set ups are essential. That what those back focus cards are for. Other references can be used at a pinch, such as news print at 10 yards. Set the camera up with something like news print on the wall, zoom in 100%, focus, zoom out 100%, focus again with the lenses back focus adjuster, repeat until both full zoom and full wide are in sharpest focus, lock back focus adjuster. Prime lenses can also be used.

8 years, 2 months ago - Mark Wiggins

I assume when you say everything in focus you mean very ddep depth of field; the infinity witness mark is a different thing and does not mean everything will be in focus when you set the lens to that mark. It is impossible to get everything in focus anyway as every lens has a minimum focus distance.

To get as much as depth of field as possible you have to use the smallest apature you can; the smaller the apature, the greater the depth of field. This means you have to use as much light as possible and/or set your camera to the highest ISO you can (not to be recommended shooting with too high an ISO as it will look very noisy).

There is an an ap you can get called PCam which will help you work out focus stuff. Used by focus pullers everywhere.

8 years, 2 months ago - Mark Wiggins

By the way, I should have said that every lens has a hyperfocal distance. This is the distance that you should set the lens to in order to achieve maximum depth of field. This distance will vary according to what apature you are using (also what lens). PCam will tell you what the hyperfocual distance is for your particular lens and and apature you are using. Back in the day when I was focus pulling (before aps like PCam) we used to use something called a "Guild Kelly" to work these things out (Google it). PCam is just a digital version of this (and a lot more).