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Icaro Hogue
The way AR Ruler works is as follows: with your Android device's camera, the app will detect different surfaces and reference points to measure. Once it has detected a surface, you have to tap on it for the tool to begin measuring. By tapping on the screen again, you can create two reference points to establish the measurement from.
AR Ruler lets you measure vertically as well as horizontally. It also recognizes circles, which means you can measure the diameter of, for example, a table. In the same way, you can calculate the cubic meters or the angles in a room. What's more, as you add measurements, a 2D plane will be generated separately, and you can consult that at any time. In that plane will appear all the reference points and the measurements between them. In the settings you can also set which measurement system you want to use and you can also save and download the planes that you generate.
The $139.95 LensAlign Pro is a focusing target with three planes that you can mount to a tripod. The $79.95 Lite model uses just two planes. It's designed to help you align the sensor plane parallel to the upright focusing targets and to indicate, on a ruler, the amount of back or front focusing your camera/lens combination suffers.
Some homebrew solutions advise you to focus on a tape measure running away from you on the floor, the camera held at a 45 degree angle. But as Westfall points out, "doing so will degrade the consistency of the camera's focusing measurement." Trying to autofocus on a single line on the tape measure, the autofocusing system (which is just multiple pairs of linear pixel arrays) only a few pixels from each active pixel array be able to see the target. "Ideally," he recommends, "the contrast in the reference target should cover the entire area of the camera's center focusing point, and the reference target should be perfectly parallel to the camera's focal plane."
That, in a nutshell is what LensAlign does. It provides a reference target you can easily align parallel to the sensor plane of your camera with a "tape measure" along side that reports the actual deviation. Tapes has hired two guys to do the job of William Tell's son: one to be the target and the other to say, "Ouch!"
Changing the angle of the ruler can make it easier to see the depth of field being captured. A steeper angle gives more units of measurement for any given depth of field compared to a flat angle. Flattening the ruler gives you fewer units.
That just makes it a little easier to see where on the ruler is the sharpest focus. You can certainly just look at the original image (even on the camera's LCD). In either case, you should view the ruler at 100 percent.
Because the values on the ruler do not correspond to the +/-20 units in your camera's adjustment, you simply have to work by trial and error. Positive values move the focal point away from the camera while negative ones move it closer.
The real challenge to using LensAlign correctly is at the camera where a number of options have to be neutralized to make sure the image reflects focus and not some other feature. These include image stabilization, focus mode, focus tracking and autofocus start point. But that's true of any method you'd use to measure focus.
I would like to know where the focus plane is measured from? When a lens says it will focus at closest a distance of 28 inches, where does that start? My power of deduction, which is sometimes faulty, tells me that it is on the rear element, but I do not know if that is correct.
I've never used my camera to do anything macro and a customer recently asked me to do some close up work. I ask about the focus plane because I'd rather calculate my depth of field with a tape measure in this instance because the pace of this project will be very fast and I want it to be perfect.
The distance being measured is from the the film/sensor plane to the object to be photographed. W/ my M3 the measuring point I use for the the focal plane is the back of the accessory shoe. I measure from there to the object in question. Works for me & the back of the accessory shoe is a convenient place to put the hook @ the end of a measuring tape or a measuring rule.
My 35mm Summicron w/ goggles set @ 0.7 meters has the images coincide @ the edge of a dark object placed 0.7 meters in front of that point. This test requires a light background behind the object being measured. The measurement is done by moving the object to be measured back & forth over the measuring tape & putting it down where the images coincide.
AR Ruler app uses augmented reality technology (AR) to tape measure room, home, house, homescapes with your phone camera. Target aim on the detected plane and start to use AR tape measurement tool. Try to room scan and floor plan your house with a new computer technology.
All measurements are hidden when another tool is selected.They are shown when the Measure tool is selected again.However, you can do editing operations while the ruler is active.For example, you can edit the rotation or scale of the selected object in the Sidebar.
In Edit Mode only, there is also a Measurement group in theViewport Overlays popover.Using the settings in this group, you can have the viewport automaticallydisplay measurements for selected edges and faces, without the need tomanually create a ruler.
To get absolute measurement in real units (e.g. "those two points are 6.23cm apart") one last thing is needed - a reference scale. In the picture below the distance could be 10cm, and the object a toy car, or it could be 2.8m and represent a real car. This problem is easily solved by measuring one or more scales (ruler, tape measure, other distance/survey device) and adding that to the photogrammetric project.
Relating pixels to distance is more difficult. Sometimes you know the size of your object: For instance, if you filmed a basket ball, you can measure the circumference of the ball with a tape measure and that gives you the diameter of the ball. Or, if you film a car or aeroplane, the manufacturer's website may tell you the length.
You may have to use geometry. For instance, to measure an object at distance D from your camera, at right angles, you could position a ruler at distance d from your camera and multiply the distance measured on the ruler by D/d. We measured pixels in the plane of the exterior of the train, not in the plane of the door, because we wanted to use train windows later as reference points and the windows are in the plane of the exterior of the train.
Measured against a clock, the frame rates of typical phone cameras are rather accurate (they have a crystal oscillator). The movie contains 30 frames per second. A first estimate of the uncertainty for the time measurement is 1/30 s, because it low light the camera may record over most of this duration [1]. It is common to give your measurement as (value) (uncertainty). The actual value can be above or below the value you give as your measurement. Therefore the time measurement for our movie could be given as (value) 1/2 *1/30 s, or (value) 0.017 s.
To measure large distances, such as the distance of a planet or a star from Earth, astronomers use the principle of parallax. Here, the term parallax is the semi-angle of inclination between two sight-lines to the star, as observed when Earth is on opposite sides of the Sun in its orbit.[a] These distances form the lowest rung of what is called "the cosmic distance ladder", the first in a succession of methods by which astronomers determine the distances to celestial objects, serving as a basis for other distance measurements in astronomy forming the higher rungs of the ladder.
Other individual objects can have fundamental distance estimates made for them under special circumstances. If the expansion of a gas cloud, like a supernova remnant or planetary nebula, can be observed over time, then an expansion parallax distance to that cloud can be estimated. Those measurements however suffer from uncertainties in the deviation of the object from sphericity. Binary stars which are both visual and spectroscopic binaries also can have their distance estimated by similar means, and do not suffer from the above geometric uncertainty. The common characteristic to these methods is that a measurement of angular motion is combined with a measurement of the absolute velocity (usually obtained via the Doppler effect). The distance estimate comes from computing how far the object must be to make its observed absolute velocity appear with the observed angular motion.
Measurements made by viewing the position of some marker relative to something to be measured are subject to parallax error if the marker is some distance away from the object of measurement and not viewed from the correct position. For example, if measuring the distance between two ticks on a line with a ruler marked on its top surface, the thickness of the ruler will separate its markings from the ticks. If viewed from a position not exactly perpendicular to the ruler, the apparent position will shift and the reading will be less accurate than the ruler is capable of.
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