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10-21-2010, 10:05 AM   #1
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? how to measure distance from camera to subject...

... why this question popped into my head is in itself a puzzlement...
i was wondering if there is any methodology in determining the distance between myself (and camera) to the subject i am/want to shoot....
there's a beautiful great blue heron, and i try to get as close as possible when shooting... i know the closer i get , the better the shot (less cropping, better i.q.)
.... this may be an easy question to answer, i'm stupified as to what it may be..
sorry in advance if this is an inane post.....
dave m

10-21-2010, 10:14 AM   #2
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Well, you may have a distance scale on the lens, though that will be an approximation at best.
You can get electronic "tape measures" from many home building stores, and probably, though I have never checked, longer range rangefinders from places that cater to hunters (who also need to know this kind of stuff).
10-21-2010, 10:21 AM   #3
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QuoteOriginally posted by Wheatfield Quote
Well, you may have a distance scale on the lens, though that will be an approximation at best.
You can get electronic "tape measures" from many home building stores, and probably, though I have never checked, longer range rangefinders from places that cater to hunters (who also need to know this kind of stuff).
..
thanks... i should've mentioned that i'm using the pentax fa300mm f4.5...
never dawned on me to check the distance scale... unfortunately only goes to a max of 60 feet... then the next setting is like buzz lightyear...to infinity !! (and beyond)..
i'm currently using my k-x (dreamin' of the k-5) and try to fill the viewfinder as much as possible to get the closest shot possible (as well the the review display)....
regards, dave m
10-21-2010, 07:13 PM   #4
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why do you care? Is it to tell people how close you were when getting a particular shot?

In regard to your Heron. you creep as close as you can until... you fill the frame or... it flys away!

there are formula's to work this out if you know some of the parameters (ie lens angle of view and size of objects in the frame)

10-21-2010, 07:18 PM   #5
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Something similar to a golf rangefinder would work well. You could ask you friends, maybe they have something like that, I know some of mines do anyway.
As for me, I'm not good enough of a golfer to bother carrying a rangefinder, plus I prefer to evaluate the distance the old way (that was out of subject though...).
10-21-2010, 07:24 PM   #6
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My rangefinding is simple, It's too far away if I can't see it and too close if it sees me and flys away.
10-21-2010, 08:32 PM   #7
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Everything is "...about a furlong away".
10-21-2010, 09:49 PM   #8
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QuoteOriginally posted by dcmsox2004 Quote
... why this question popped into my head is in itself a puzzlement...
i was wondering if there is any methodology in determining the distance between myself (and camera) to the subject i am/want to shoot....
there's a beautiful great blue heron, and i try to get as close as possible when shooting... i know the closer i get , the better the shot (less cropping, better i.q.)
.... this may be an easy question to answer, i'm stupified as to what it may be..
sorry in advance if this is an inane post.....
dave m
Your example is easy, when it flies away you've got too close Nothing beats having surveyed the site before and taken test images. You soon learn what distance is acceptable to you. With bird shots I find the distance will change dramatically with the quality of light / contrast

10-21-2010, 09:54 PM   #9
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Bring two Boy Scouts, and a piece of study string exactly 200 feet long with a knot in the center, and two protractors from math class.

Position the knot of the string directly in front of your belt buckle, and have one Boy Scout on each end of the string 100 feet away directly to your left and right.

Each Boy Scout must carefully align their protractor flat along the string, then carefully read the angle to your intended subject.

Now, using that angle-side-angle stuff from geometry, you can figure out the height of the triangle with a base of 200 feet, i.e., the string. If no calculator or reference table is handy, you can make a scale drawing, using a 6 inch long base. Simply draw the other sides at the angles as reported by the Boy Scouts. Then, measure perpendicularly from the base to the apex. Multiplying that length by 400 will give you your final real-world distance.

This is the method used to calculate the height obtained by model rockets, though the base was much longer.

You might have the Boys Scouts write down their measurement on notebook paper with a big felt pen and show it to you, so they don't scare off the birds by yelling.

Good luck :-)
10-21-2010, 11:15 PM   #10
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Interesting question, it would be nice to know at times for non-photographic reasons, e.g. you're out in a boat and want to know how far land is away?

You would need to know three things to figure this out:
a. What's the vertical height angle of the lens you are using, see
Focal Length: Optical: Glossary: Learn: Digital Photography Review

b. What's the vertical height of a known object in your viewfinder. For example, if there were a person standing next to the heron, you could guess an average height of 5 1/2 feet. If you knew the approximate height of a full grown heron, one could use that.

c. If you had a 100% viewfinder, you would need to estimate the approximate percentage of the vertical height occcupied by the subject in the viewfinder. For non-100% VF, one would have to throw in a correction factor.

From trigonometry, you could then calculate the distance to the object. One's estimate of the percentage of the vertical height of the heron in the viewfinder, would probably severely compromise the calculated distance.

Actually, the suggestion of using other specialized equipment to estimate distance would be a more practical approach.
10-22-2010, 01:20 AM   #11
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Mechanical-optical and laser-electronic rangefinder units abound. But let me tell you a story. Despite a lifelong exposure to photography and darkrooms, I didn't get my first *real* camera till I was 24. It was an ancient folder, a German 1934 Kodak Retina I, the very first 135 camera. Folded, it;s not much bigger than a pack of king-size cigs (gosh, those were the days!) and its controls were minimal: shutter, aperture, and focus. Nothing powered, no rangefinder, no meter, nothing.

So I got a hand-held light meter, and I taught myself to judge distance, and after awhile I learned to judge light, so *I* became the camera automation. Stare at a subject, and the old unconscious just directed my fingers to adjust the controls as needed. But gaining that judgment took rather a bit of practice practice practice.

So, how to judge distance from camera to subject? Practice. I'm a tall guy and I can pace out 1-yard strides. So for still subjects I'd pick a shooting position, then pace out to the subject, and that's the distance I'd focus to. With practice, I'd just mentally pace the distance. With more practice... well, I never reached the point where an X-yards-away number would pop-up in front of my eyes. But I can still visualize the paces pretty well, and fast. It's not trigonometry but it works for me.
10-22-2010, 01:47 AM   #12
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Interesting subject.....
Well within the lifetime of many adults today, distance measuring involved either muscle work (long measuring tapes & chains) , or a complicated mathematical exercise (theodolites & surveyors tables) or complex optical rangefinder equipment.

Now we have handheld laser rangefinders....just look through the eyepiece and press the button...
10-22-2010, 06:40 PM   #13
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QuoteOriginally posted by Wheatfield Quote
Well, you may have a distance scale on the lens, though that will be an approximation at best.
You can get electronic "tape measures" from many home building stores, and probably, though I have never checked, longer range rangefinders from places that cater to hunters (who also need to know this kind of stuff).
Golf stores will have rangefinders as well.
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