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human rangefinder card
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PostPosted: Wed Apr 27, 2022 9:05 am    Post subject: human rangefinder card Reply with quote
hi guys. I'm expecting a folding camera without rangefinder
I just learned about human rangefinder card
what I understand is, when you hold up the card with both hands straight, it has to be in between your eyes ?
I notice that if I hold one hand and not between my both eyes (slightly to the left), the distance is all wrong

to illustrate






also, what happens if the subject I want to shoot is at the left of the frame ?do I move my card to the left?


PostPosted: Wed Apr 27, 2022 9:29 am    Post subject: Reply with quote
I would have thought this rangefinder would be quite inaccurate anyway; pupillary distance varies quite a bit from person to person, between 51mm to 77mm according to Wikipedia, hence the opticians always measure it when you need new glasses. Unless you made one specific for your own pupillary distance (and arm-length), it will be wrong...

In any case, I would expect it to be even worse if you hold it to one side because of the foreshortening effect on the pupillary distance that way; it needs to be held straight in front.

EDIT: if the subject is at the edge of the frame, you can't use this method reliably; it only really works for any subject that is dead ahead of you. Remember lenses are generally corrected for a flat field, not a hemispherical field.


PostPosted: Wed Apr 27, 2022 9:35 am    Post subject: Reply with quote
ooops. I apologise for posting in the wrong forum subsection


PostPosted: Thu Apr 28, 2022 12:42 pm    Post subject: Reply with quote
I use one all the time. If you go to tomchuk.com/rf you will find a template to make your own rangefinder. Each one is different due to our interpupillary distance and arm distance. Here is how to use the template and RF card:

Go to the website.

Card title. I use the name of the lens or camera that its for. My trio of Staeble lenses (35, 50, 135) all have the same distances engraved so only one card is needed.

Measure the distance between your pupils. Its best to get someone to do this for you. Focus your eyes to infinity if you can so they're not converged. Note that on the template.

Measure the length of your arm. Hold a card in your RIGHT hand at right angles so that you can see it. Line the card up with your RIGHT eye. Measure the distance between your eye and the card. Note that on your template.

Enter the focus distances as printed on your lens in metres or feet. Separate each distance with a comma e.g. 1,1.5,2,3,5,10,20 (metres).

Its useful to have a hyperfocal distance chart for that particular lens too so check the 'hyperfocal dist chart' Then enter the details of your lens in there. I used a 35mm f2 as my example.

Click on the card to download. It will download as a pdf. print it actual size and cut it out. I laminate mine

To use:
Hold the card in your right hand (just as you measured your arms length), close your right eye and line up the 0 (zero) symbol with the object to be focused on. switch eyes, The object will now appear somewhere in the focusing scale. Note it and set that on your lens.

The hyperfocal distance chart gives a rough fixed focus distance for each aperture used. With my 35mm set a 5 metres at f8 I'll get infinity down to a couple of metres. There's more info online about hyperfocal distance. I use it mainly for middle distance to infinity shots.

Hope this helps you. Remember a chart made for someone else wont work for you.



PostPosted: Thu Apr 28, 2022 12:47 pm    Post subject: Reply with quote
RokkorDoctor wrote:


...EDIT: if the subject is at the edge of the frame, you can't use this method reliably; it only really works for any subject that is dead ahead of you. Remember lenses are generally corrected for a flat field, not a hemispherical field.


Using the card I suggested : Hold the card in your right arm and turn your body to the subject, measure the distance, then frame your camera. The distance wont vary.


PostPosted: Thu Apr 28, 2022 7:26 pm    Post subject: Reply with quote
philslizzy wrote:
RokkorDoctor wrote:


...EDIT: if the subject is at the edge of the frame, you can't use this method reliably; it only really works for any subject that is dead ahead of you. Remember lenses are generally corrected for a flat field, not a hemispherical field.


Using the card I suggested : Hold the card in your right arm and turn your body to the subject, measure the distance, then frame your camera. The distance wont vary.


I think we were talking cross-purposes; I was thinking about the use of the human rangefinder card to work out the required focus distance for a camera; I think you are talking about the use of the card for finding the subject distance. That isn't just a matter of semantics; if the subject is at the edge of the frame when using a (reasonably) flat-field corrected lens, subject distance is different from the required focus distance. This is a well-known problem with wide-angle lenses when using focus-lock on a camera without selectable focus points and then re-framing.
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