How foolproof is focus using measuring tape and distance in viewfinder?

mainstreetprod

mainstreetprod

Veteran
I've seen a lot of posts complaining about the difficulty of focusing the AF100 and now that I own one, have experienced it firsthand. How effective is the tried and true method of using a measuring tape and setting the focus to the measured distance? I used red peaking to focus on a subject 4.5 feet away and it had me focused at 5.5 feet.
 
Using a measure would depend on the accuracy of the datum enscribed on the lens.

IMHO - a stills lens (and an adapter) would be way off and unreliable.

Best solution is red peaking and a great field monitor.(Thats the digital way)
 
With all the digital tools available in our cameras and external monitors using a measuring tape seems time consuming and potentially less accurate.
 
Unless you are using something like PL lenses or other real cine lenses with a high quality mount with dead on proper flange distances with everything properly calibrated (which most AF100 users are not), you are not going to get accurate readings off the lens distance engraving. The engraving in still lenses are just there for reference and as a rough guide, they are not really accurate for measuring focus like the markings on cine-lenses are, but as I said, even those require 100% proper flange distance/backfocus to be truly accurate.

In short, trust the camera tools, and use an external monitor if anything for focusing.
 
If you wish to a use Measuring Tape for Focus, you need to be fairly confident that the Camera, Lenses and any Adapters are set up correctly:

Lens Collimation - You'd need to make sure your Lenses are Collimated - this means that they are checked to make sure that they Focus sharply at Infinity and then at distances given on the Focus Scale, and for Zoom Lenses (that can), that they hold Focus throughout the Zoom range. A Lens Engineer, Camera Engineer or Tech should be able to do this for you. A good Focus Puller or even yourself - if you have a decent large Monitor, should be able to check out the that the Focus Scale on the Lens is accurate - if it's not you can put a piece of Camera Tape around the barrel of the Lens and mark up an accurate scale yourself - I'd prefer to get someone well experienced to do this. The overall Collimation should be checked on a Collimator.

Adapters - Any Lens Adapters you are using should be checked by an Engineer to make sure that they do not affect your Focus adversely. Some do have Focus Adjustment, some come with Shims to ensure the right fit. This is not really something you can do completely accurately yourself by eye. You should get a Lens/Camera Tech/Engineer to perform the adjustments and cut or make any Shims required.

The Camera Lens Mount itself should be checked for accuracy. If this is even slightly out it will throw of your Focus.

We are talking microns of tolerance here, so you really need someone with a Collimator and correct measuring equipment who knows what they are doing. This shouldn't really be an expensive service.

If all these things are set up to be accurate then using a measuring tape is completely foolproof, though possibly a bit time consuming.

Nothing wrong with this method, worked for over a century on Film and is still used a lot on Film.

At the end of a long days Shoot when your eyes are tired, which is more foolproof? Staring at a tiny 5' Monitor with the Sun glaring of it trying to see peeking or a tape measure?


Neil.
 
Its optimize optical focus for me . Pl adapters have to be checked for proper flange depth and PL lenses for collimation before you start putting absolute faith in tape measures. In the feature world there is such a thing as a "check out" which is a very methodical of the whole photographic chain prior to shooting . I doubt many people do that here, as most are happy to slap on their adapter with a lens and shoot. After all we have quality live viewing and play back which you don't always get with film camera.
 
Might be something lost in the translation here- as the subject line said, I'm using a measuring tape and setting the distance displayed in the viewfinder to that measurement, when using a MFT lens. I have some still camera lenses and adapters but don't use them that often. When I do, though, I've found it much easier to snap to focus than when using Panasonic lenses. I think I will have to invest in a camera top monitor soon, focusing is just too iffy. I think with one of these, if connected via HDMI, I could focus effectively- IF I could zoom in and focus, then zoom out. But none of the affordable lenses for the camera are really parfocal.
 
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