Using Tape Measure For Precise Focus

[Jeff Kellam]

Originally Posted by Alan Craig

Peter, if you look at your lens there is a red line around it as I think there is on all canon lenses I Think jvc rings are green and I am sure that that is your focal plane and that is where you take measurements from but don't take that for gospel I have never used a tape to focus.

Alan

With the electronic focus I really don't think it will matter if you measure from the front or back of the camera or where your cup of coffee is sitting. There are no hard stops or marked rings to even use for adjustments.

You need a monitor.

[Alan Craig]

Jeff you are probably right and digital cameras have a large DOF, I dont know whether using a 35mm adapter would make a difference with its shallower DOF never used one but as you say the electronic focusing is probably as good as it gets. Like I said in my post I have never used a tape I have allways relied on IAF or manual focusing using the lcd or viewfinder, as for the monitor nice if you have one but can't always carry one out in the field as you could not always use a tape out in the field but do take your point. Now for Colins benefit I am Pretty sure that the line I mentioned in my post is where you should take measurements from which was the original question hope that answers your question if anyone knows different please chime in.

Alan

[Philip Younger]

I can't understand your problem. I have just interviewed 16 people as part of a project I'm working on mostly framed up from the waist up camera between 4- 7 feet from the subject (I like to get as far back as I can and zoom in slightly - comes from my stills photo days - but not always possible) I put the camera in auto and had no problem whatsoever, perfectly focused.

One the of problems I foresee in a tight manual focus is people leaning and shuffling especially if your aperture is fairly wide open (i.e. no depth of field).

I know many people in this forum disagree with me for using auto settings as much as possible but if it works, it works, why try to 'be the pro' and mess about with tape measures and focus rings if you don't have to just because it is deemed to be the 'professional' way of doing things surely the point is to obtain the satisfactory result

[Richard Hunter]

Originally Posted by Alan Craig

Jeff you are probably right and digital cameras have a large DOF, I dont know whether using a 35mm adapter would make a difference with its shallower DOF never used one but as you say the electronic focusing is probably as good as it gets.

Hi Alan. Yes, a 35mm adapter makes a big difference. Apart from the shallow DOF, which is of course the main reason for using one, the adapter brings its own focussing plane, which is the ground glass element. If you want to use a tape measure, you need to use the ground glass as the reference. You also need to make sure the adapter and front lens are collimated so that the distance markings on the front lens match up with what the tape measure says.

And you need to focus using the front lens only, the video cam lens focus should stay fixed on the ground glass.

Richard

[Jonathan Shaw]

Also when zoomed in if you overexpose the image then focus and then close the iris to the correct exposure it will be hopefully more accurate due to the DOF increasing.

[Peter Dunphy]

Originally Posted by Jonathan Shaw

Also when zoomed in if you overexpose the image then focus and then close the iris to the correct exposure it will be hopefully more accurate due to the DOF increasing.

this is interesting - what camera settings would you suggest?

eg. TV or "A" setting?