Angenieux 12-120mm Focus

Scott Bryant · April 5, 2009

I was working on focusing with my angie lens on my NPR and a buddy of mine said an easy way to focus at the wider angle end of the lens (12mm) is to zoom all the way in to the 120mm and focus then zoom back out. I seem to remember seeing somewhere on here that the technique he mentioned doesn't always work with certain lenses (I couldn't find the post however). Does anyone know if my angie will be capable of doing that or will I run into focusing problems due to lens movements inside the barrel?

Saul Rodgar · April 5, 2009

It is been a few years, but my Angie 12-120 mm focus fine across the entire zoom range. I cannot speak of all the lenses out there, but all of mine do the same, so if your lens is in good mechanical condition there is a good chance it will focus fine.

Also you have to remember that focus is more forgiving the wider the lens, generally speaking. And also the size of your image area matters, the smaller the image area the more depth of field you get. So for 16 mm format filming with a 12 mm lens, pretty much everything will appear in focus some 6 to 8 ft away from the camera to infinity, even at the widest aperture T2.2 of your Angie 12-120 lens.

Generally speaking, the bigger the sensor or film area, the narrower the lens (telephoto) and the greater the lens aperture (or smaller the f / T stop number) the more critical the focusing becomes.

Chris Keth · April 6, 2009

Do you know anything about the condition of the lens and the camera. Has the lens been collimated? Has the flange focal depth been properly set on the camera?

If the answer to both of those questions is "yes" then you'll be able to count on zooming in to focus and the lens holding focus throughout its range. if the answer is "no" then who knows what will happen.

Scott Bryant · April 6, 2009

Do you know anything about the condition of the lens and the camera. Has the lens been collimated? Has the flange focal depth been properly set on the camera?

If the answer to both of those questions is "yes" then you'll be able to count on zooming in to focus and the lens holding focus throughout its range. if the answer is "no" then who knows what will happen.

I just got the lens back from Bernie so it's collimated and everything. I didn't know if that would be a factor or not. So it sounds like I should be good to go then.

Chris Keth · April 6, 2009

I just got the lens back from Bernie so it's collimated and everything. I didn't know if that would be a factor or not. So it sounds like I should be good to go then.

That's half the equation. How is the flange focal depth of the camera?

If that is off, you'll usually be able to eye-focus and I think you'll even be able to zoom in to focus but your eye-focus won't agree with tape-focus, if that matters to you. If the FFD is off in one direction, you won't be able to focus on infinity, the other way and the lens' close focus will be further away than stated.

Tom Jensen · April 6, 2009

A little off topic but close enough. If you suspect that your flange focal depth is off, stick to the long end of the zoom. Because the "depth of focus" is greater with long lenses you will have a better probability of sharp focus than you would with a wider lens.