Hyperfocal focusing with a scale focus folder: Need a primer...

[bliorg]

I have never been any good at guessing distance with scale focus cameras. I'm finishing off a dual-format, pre-war Isolette, and not only is it scale focus, but the scale's in meters. I need hyperfocal focusing.

So, there's a red triangle on the aperture scale around the f/8 mark. There are two red lines on the distance scale, at 3 and 10 meters. What do I do with this info?

Any help, in what's I'm positive is a basic procedure, would be greatly appreciated.

Thanks,
Scott

 

[David William White]

Not sure what to do with those markings, but if you've got 15 minutes free, you can make your own.

The hyperfocal point is at 1000 apertures, from basic theory. So say you've got an 80mm lens and will be using it at f/16, then your hyperfocal point is at 1000*(80/16) = 5 meters.

So you put the camera on a tripod and open the back. Mark off an object 5 meters away with a tape measure. Put some glassine or even scotch tape across the film gate, simulating a ground glass. Open aperture all the way, open the shutter on bulb, and focus the lens on your point 5 meters away. Mark the distance scale.

Now everything from 2.5 meters to infinity should be in reasonable focus at f/16 when you are set at your mark.

Actually checking the hyperfocal point by direct viewing as the film would see it gets around any scale problems -- like if the lens were remounted and the scale cannot be trusted. Your mark may line up at 5m, but if it's been tinkered with, it might not. Best to check this way to be sure.

 

[Diapositivo]

The marks on the focus scale are usually there to serve as simple references for two situations: portrait (one) and groups. There might be a third mark near infinite which is the hyperfocal distance. For instance my Voigtländer Vito CLR has a red dot on 1.3 metres (that's for portraits, 4.25 feet), a red triangle slightly after 3 metres (that's for small groups, 11 feet) and a red circle meaning around 11m (that's I suppose the hyperfocal distance with a certain diaphragm, such as f/8, and for a certain circle of confusion, and is indicated as "landscape", 33 feet).

Certain cameras of the time did not have a scale distance but only symbols such as one person (bust, head), three persons, "landscape". "Landscape" is not infinite but hyperfocal distance.

So in your case the line at 3m means "small group of people" and the line at 10m says "landscape" (hyperfocal, within certain conditions).

It goes without saying that if you don't have a particular interest in a near object, and only need the correct focus on infinite, you should set infinite. Hyperfocal distance is a tricky thing as it is generally calculated for a circle of confusion "almost good enough".

Nice considerations here:

http://www.trenholm.org/hmmerk/DOFR.html

Fabrizio

 

[bliorg]

Okay, that makes sense. Also, I looked up a manual for the 4.5 Isolette. They describe using the two red marks (which are the same scale, though the discussion is in feet, weird) for near and far focusing. Essentially, use the red "3" for anything 8 to 15 feet away, and the red "10" for anything 15 feet to infinity. This is for use with the f/8 mark, or smaller aperture. Just need to commit that to memory now...

 

[ic-racer]

You can use your eyes as a rangefinder based on your interpupillary distance and arm length. This really works well, its not just for Minox:
http://tomchuk.com/rf_hfd/

Hyperfocal distance is OK for little prints at a distance, but if you are printing that way, why use a big negative? If you want to do 16x16" prints you may like the results better if the subject is in focus. Also, while using the camera with a tripod you can pace out the steps to the subject or even use a tape measure.

 

[Ian C]

Hyperfocal Focusing Table for 85mm f/4.5~f/22 lens for 6x6cm format (circle of confusion c = 0.059mm).

The entries are: aperture, hyperfocal distance (actual distance focused), the near limit of acceptable focus (1/2 the hyperfocal distance), bellows increment Δ beyond the infinity position.

f/4.5, 27.3m, 13.6m, 0.27mm

f/5.6, 22.0m, 11.0m, 0.33mm

f/8, 15.4m, 7.7m, 0.47mm

f/11, 11.2m, 5.6m, 0.65mm

f/16, 7.7m, 3.9m, 0.94mm

f/22, 5.7m, 2.8m, 1.3mm

Example: You want everything acceptably sharp from 7 meters to infinity.

From column 3 in the table, you see that you’ll have acceptable sharpness from 7.7m to infinity at f/8 at the hyperfocal distance.

Set the shutter for correct exposure at f/8. Set the focus as close as possible to the f/8 hyperfocal distance 15.4m.

If that’s not easy, then you can first set the lens to infinity and then move it forward 0.47mm with the aid of a millimeter pocket scale.

 

[blockend]

If you're using your camera for street work it's worth marking two hyperfocal ranges with Tippex on the lens barrel. One that will encompass close ups, say, 4-12ft, and a second mark at 15-infinity. I recently bought a separate rangefinder that mounts on the cold show for my folders. You align the image, read off the distance and set it on the lens, but it slows things down considerably and with fast film isn't necessary.