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Post by seth24 on Jun 16, 2014 17:18:17 GMT 10
I would say these markings ARE very faint but quite distinguishable stripes. I couldn't tell ya what they are to be honest, the marks could be anything Got less certain over time? Starting with your own example of the brindle dog, if I crop the photo to the right place I can find 5 relatively "consistent" (I use the term loosely) stripes. If the trail cam had happened to target that portion of that dog we could be sitting here arguing this animal was striped. I use the term "consistent stripes" loosely because if you make a fair analysis of the mystery animal in question, the "stripes" are not all the same thickness, or darkness; nor do they extend to the same length - either up onto the spine or down to the belly. Maybe we are looking at it wrong, another perspective of the image, "maybe" the "ends" are around the other way ie: hips front of animal and shoulder back of animal. "stripes" seem to be evident from middle back to what is suggested the front of the animal. just a thought. in this case the animal would be walking towards the camera.
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Post by mingle on Jun 16, 2014 18:34:23 GMT 10
I'd say the motion-blur on the subject definitely indicates right-to-left motion - ie: the 'head-end' is on the left...
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Post by youcantry on Jun 20, 2014 13:02:54 GMT 10
I'd say the motion-blur on the subject definitely indicates right-to-left motion - ie: the 'head-end' is on the left... I feel likewise, but how do you "measure" that and say "because of features xyz, this indicates left to right motion"?
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Thylacoleo Gal
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Thylacoleo Gal
The Singularity is near.
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Post by Thylacoleo Gal on Jun 20, 2014 13:05:17 GMT 10
I'd say the motion-blur on the subject definitely indicates right-to-left motion - ie: the 'head-end' is on the left... I feel likewise, but how do you "measure" that and say "because of features xyz, this indicates left to right motion"? Need to know the shutter speed and make some plausible assumptions about how close the critter was & how fast it was moving.
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Post by youcantry on Jun 20, 2014 13:07:39 GMT 10
I wanted to take the illustration one step further. The trail camera has produced a greyscale image. I believe the selection of the shades of grey is related to the temperature, or infrared light reflected by each point in the image, so the below comparison is not 100% fair (because my generation of a greyscale version of the dog was simply the software's choice at converting colour pixels - nothing to do with temperature or infrared light) Nonetheless, here is that dog in greyscale. (As an aside, I think it's precisely because IR images from trail cameras have to do with temp/IR that sometimes the apparent colouration of objects/animals in IR images looks totally wrong - because we humans are used to interpreting colour, or shades of light/dark; we are not used to shades of light/dark representing something we cannot see).
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Post by youcantry on Jun 20, 2014 13:14:34 GMT 10
Need to know the shutter speed and make some plausible assumptions about how close the critter was & how fast it was moving. But still - how do you get from that to a conclusion about direction of travel? Take a look at this bird photo: See how it *looks* like the snow is falling upward? There is a reason for that (and it is explained well on the source page, here: www.digitalbirdphotography.com/7.2.html ) In a nutshell, flash was used to take the photo, but the shutter was open for longer than the flash fired. When the flash fired, the snowflakes were "frozen" and are clearly defined. Because the flash fired at the beginning of the exposure, the flakes continued falling after the flash turned off - and it is this motion of the flakes that was recorded as a trail/streak/tail, underneath the point at which the flake was "frozen" (no pun intended) by the flash. So.. along the lines of your suggestion - *if* we could confirm the exposure time, and *if* we could confirm the start and end time of the flash firing, and *if*, in that case, the flash fired for less amount of time than the shutter was open, and *if* the flash was not on at the very least either before the shutter opened or as the shutter closed, and *if* the shutter opened more towards the beginning or the end of the exposure than in the middle (and *if* the manufacturer could guarantee the consistent sort of quality you'd expect from a DSLR) *then* we could look for a similar effect in this image and draw a measured conclusion about direction of travel, imo.
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Post by youcantry on Jun 20, 2014 13:16:04 GMT 10
Oh, and *if* there was enough light to render an image while the flash was off.
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Post by youcantry on Jun 20, 2014 13:22:41 GMT 10
What we'd be looking for is a sharp edge to some portion of the moving animal - say a stripe. The mesh fence shadow is most fortuitous because in all probability that mesh did not move - so the edge of the mesh gives us a measure of what a "sharp edge" should look like (ie, in this case from an unmoving object, which is what the moment at which the flash fired should look like). If we have a sharp edge at one end of the motion-blurred stripe, but a soft edge at the other, then we're in luck. In all honesty I think the left edge is sharp and the right edge is blurry - at a number of points (though not all, but a majority). (Aside - note, mingle, TC_gal, that in the bird photo, you would conclude the snow was falling upward, no? Just by visual inspection? ) So, without knowing the camera specs, I'm going to *assume* right to left motion. To be blurry first, then end with a sharp edge suggests the camera's shutter opened before the flash fired, and/or the flash fired toward the end of the exposure. I'll send Reconyx an email and ask if they have this info. If it's the other way around then the animal was moving left to right.
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Post by mingle on Jun 20, 2014 13:57:40 GMT 10
(Aside - note, mingle, TC_gal, that in the bird photo, you would conclude the snow was falling upward, no? Just by visual inspection? Actually, I didn't think that bird photo showed motion-blur, as the snowflake that's been captured by the flash is quite clear and it's only the 'trail' of the unflashed flake that suggests movement. Proper motion-blur will affect all parts of a moving object equally, unless of course certain parts are moving faster/slower than others. To be motion-blur, wouldn't that photo be showing snowfalkes that suddenly stopped mid-movement? :-)
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Post by youcantry on Jun 20, 2014 14:07:14 GMT 10
Actually, I didn't think that bird photo showed motion-blur, as the snowflake that's been captured by the flash is quite clear and it's only the 'trail' of the unflashed flake that suggests movement. Proper motion-blur will affect all parts of a moving object equally, unless of course certain parts are moving faster/slower than others. To be motion-blur, wouldn't that photo be showing snowfalkes that suddenly stopped mid-movement? :-) Huh? "It's only the 'trail' of the unflashed flake that suggests movement" - so yes, this is motion blur. The blur was stopped by the flash at the top of the flake's fall - but just look at the photo: at a glance, doesn't it look like the flake is falling upward? This is because our brains are accustomed to the 'trail' being behind the object that is moving - so our brains interpret it that the flake is moving upward: "look, here is the trail, and here is the flake at the top, so the flake moved from bottom to top". But the effect is a consequence of the configuration of the camera, and our instinctive interpretation is wrong. I'm saying the same could be true for the dog image. You and I both feel like it is moving right to left but (I'm proposing) we also both feel like the snow is falling upwards - but it's not. We're wrong in the snowflake interpretation (if I may assume you agree it looks like it is falling upward), and so too we can be wrong in the interpretation of right-to-left movement. To objectively draw a conclusion about direction of travel, I think the technical setup of the camera needs to be known. "Proper motion-blur will affect all parts of a moving object equally, unless of course certain parts are moving faster/slower than others." - they will still be "properly" motion-blurred, though different portions at different rates. Blur depends not only on the object's movement, but the amount of time the opened shutter is illuminated sufficiently to render an image. "To be motion-blur, wouldn't that photo be showing snowfalkes that suddenly stopped mid-movement" - you've lost me. Don't really understand what you're asking. That photo shows flakes which were illuminated for a fraction of a second by a flash unit at one point during their movement, *and* a motion-blurred rendering of their movement after that moment in time (because the flash fired soon after the flash shutter opened; had it fired toward the end of the flash shutter opening, the "motion-frozen" rendering of the snake would have appeared toward the end of its fall, not its beginning). Aside - all flakes show the effect here.
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