Re: An unedited clip of a weather balloon ascending to space, without fisheye.
« Reply #20 on: September 25, 2020, 02:28:02 PM »
I think we are all missing the point here. All debate is being focused on one screenshot, and whether the observed curve (surely we can at least agree that there appears to be a curve) is a product of optics or an observation of a round earth. But I didn't post a screenshot. I posted a link to an unedited 2 1/2 hour-long video from the ground to the apogee to the ground again. If you look at the video right after the garlic bread breaks through the clouds, at about 3.1 km, you can see that the horizon essentially appears flat. Take a screenshot and kick up the contrast for a better view.

Then if you look again at 15 km, a subtle curve is visible.

Finally, at the highest point, you can clearly see a curve.

How could a camera artifact account for a changing curve? Just interested ;).

Additionally, I don't think anyone has made any claims to the diameter of the earth:
...claiming that the Earth is round but 5 times smaller than in RET, or demonstrating your excellent knowledge of geometry as you did above, you're guaranteed to blow me away.
Also, just wanted to point out this:
EDIT: I note that I've been referring to these curves as "arcs" which may be a bit hasty - they could be arcs, but they might not be depending on the specific situation. I'll leave the phrasing as-is since it doesn't particularly affect any of the underlying reasoning, but it's only fair that I highlight that inaccuracy.
Word choice does not necessarily affect an argument. I used the term "fairly straight" because if I had used the word "perfectly straight" I would have been lying. It's not perfectly straight, there's a slight distortion. However, it's much closer to straight than the screenshots from 35 km.

Looking forward to your response :)

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Re: An unedited clip of a weather balloon ascending to space, without fisheye.
« Reply #21 on: September 25, 2020, 04:21:41 PM »
Please fix your image links. People shouldn't have to reverse-engineer your post just to be able to figure out what point you're making.

Take a screenshot and kick up the contrast for a better view.
We cannot know what that line actually is. It's most likely not the horizon, which is why you needed to "kick up" the contrast.

Then if you look again at 15 km, a subtle curve is visible.
Ah, yes, interesting - once the horizon appears slightly above the middle of the frame, it starts to look like it's curving a little. I wonder why that might be. I wonder why it follows the formula for barrel distortion to the tee, and why adjusting for it makes it disappear. Truly mind-boggling, that one.

Finally, at the highest point, you can clearly see a curve.
Your red line doesn't even attempt to align with the horizon here - I'm not sure if that's you being incompetent or just trying to lie. Hilariously enough, the curve here is lesser than that in your 15km screenshot. I wonder if that might have something to do with the fact that the horizon is closer to the middle of the frame.

EDIT: For the absolute avoidance of doubt, here's your screenshot with the actual horizon traced correctly:



Now, let's take my purple shape and superimpose it on your supposedly "less curved" horizon at 15km:



Blimey! Who'da thunk it. When you do things correctly, you get consistent results.

How could a camera artifact account for a changing curve? Just interested ;).
Let's start with the basics - this isn't "a camera effect". It's basic optics. "How does optics affect what we see?" is a question I sincerely consider beneath anyone here.

Additionally, I don't think anyone has made any claims to the diameter of the earth
Yes, you would think that. However, claims have consequences. If you simultaneously claim that:

  • The Earth is round
  • Your video is not subject to barrel distortion
  • It was not taken with a wide-angle lens
  • You can see a curvature at altitudes as low as 15km with the naked eye

Then only one option remains geometrically feasible - the Earth must be tiny. Of course, the alternative is that one of the claims above is false - I strongly suggest you consider that possibility.
« Last Edit: September 25, 2020, 07:41:50 PM by Pete Svarrior »
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Re: An unedited clip of a weather balloon ascending to space, without fisheye.
« Reply #22 on: September 25, 2020, 09:01:29 PM »
The ratio between the "line" and "dip" have nothing to do with the eccentricity of these two arcs. I can keep pointing out that you're wrong and explaining why you're wrong, but in the end of the day you won't accept it, because you're not interested in being correct - you just want to confirm your preconceptions.

But hey, let's keep on keeping on. Let's illustrate the issue with my previous example:

The span of the white frame is 590 pixels, and the "dip" (sagitta) of the first arc is 14 pixels.

The second arc has a span of 195 pixels and a sagitta of 1.5 pixels.

You assert that I can make these comparable through a simple ratio. Let's do that.

1.5*590/195 = 4.53

As you can see, by your logic, I should expect that the arc towards the bottom of the image is much less curved than the one closer to the middle. However, even a cursory visual comparison will reveal that not to be the case. In reality, when measured correctly, the sagitta of the second arc is 23 pixels.

Very good, Pete, I always enjoy the chance to learn something new, and found a handy sagittal calculator should anyone like to check the following figures. https://www.liutaiomottola.com/formulae/sag.htm

The arc of 715 pixels has a measured sagitta (couldn't remember the term - thank you) of 3 pixels – this corresponds to an arc radius of 21302 pixels. The same arc extended to a width of 1117 pixels would generate a sagitta of 7.3 pixels, so yes, a simple proportional calculation is wrong. So near the bottom edge of the screenshot we have an equivalent full-width distortion of 7.3 pixels and barrel distortion of a straight horizon line much nearer the middle of the image would show distortion of rather less than that.

You also entirely ignored the many issues with your "23 pixels" estimate - the line you're using as your reference point does not touch the horizon on either edge of the frame (or, indeed, at all). When adjusted appropriately, the correct sagitta is more akin to 10 pixels.

Fair point about the red line in the screenshot, so I had my own try at it. I do hope the (black) line is distinct enough this time:–



Oh dear, "akin to 10 pixels"? Did you try measuring it yourself? My point still stands – if the tray seam (assumed by both of us to be straight) has distortion equivalent to 7.3 pixels across the entire frame, an assumed straight horizon close to the middle should show much less distortion, not more than twice as much. I attach very slight importance to your claim – if these words mean anything.

The lens was an 18-135mm zoom
Do you realise how extremely wide this range is, and how useless that statement is as a result? An 18mm focal would be bordering on a fisheye lens, which this obviously isn't. A 135mm focal wouldn't capture anything remotely close to this wide an area. Before you can perform your experiment, you need to know the actual focal of the lens at the time of filming, not what the particular device is capable of.

Dear me, I should have made abundantly clear the 18-135mm zoom lens is the one that took the test image of the grid, not the view from tens of kilometers above Earth. I do apologise for the misunderstanding, the intention was to demonstrate barrel distortion in a known, measured case and yes, I do understand how wide this range is.

But do you know the film or sensor size of the camera that this zoom lens was attached to? Was it perhaps a phone? Or a 35mm camera? Perhaps a micro 4/3 DSLR, an APS-C digital camera, a medium format or even an 8"x10" field camera? I'll spare you, it was fixed to an APS-C digital camera and 18mm is a typical wideangle focal length on an APS-C camera, with a 76 degree angle of view across the diagonal. Nowhere near fisheye with this camera format and I do hope this helps you.

..claiming that the Earth is round but 5 times smaller than in RET...

Eh? You must be confusing me with someone else.

Oi now, governor. There is absolutely no need to get personal, innit.

Praise be, the man has a sense of humour! Until next time, mate.

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Re: An unedited clip of a weather balloon ascending to space, without fisheye.
« Reply #23 on: September 26, 2020, 08:03:27 AM »
The same arc extended to a width of 1117 pixels would generate a sagitta of 7.3 pixels
It'll be a bit more complicated than that - to get any number for direct comparisons, we'll first need to establish which barrel distortion formula to use. This is one of the reasons why I'm advocating for a visual solution, rather than a numerical one.

Oh dear, "akin to 10 pixels"? Did you try measuring it yourself?
I did, but I neglected to illustrate it at the time. 16 pixels is definitely pushing it. Of course, the challenge here will be agreeing on how to distinctly identify the horizon as a line where the image is (understandably) out of focus at that distance. The way I see it, your top line seems rather arbitrary - it doesn't seem to follow any arc at all, and your bottom line appears to only intersect the horizon on the right hand side. I'll draw something more appropriate later today, when I have access to software that doesn't suck.

Dear me, I should have made abundantly clear the 18-135mm zoom lens is the one that took the test image of the grid, not the view from tens of kilometers above Earth.
That still makes no sense - the lens had a single focal length at the time the photograph was taken. The range of possible lengths is irrelevant.

I'll spare you, it was fixed to an APS-C digital camera and 18mm is a typical wideangle focal length on an APS-C camera, with a 76 degree angle of view across the diagonal. Nowhere near fisheye with this camera format and I do hope this helps you.
I should be clear: I already have a good enough idea of the equipment used. That's what enables me to speak with a decent amount of confidence here, and why I recommended giving Lightroom a shot.
« Last Edit: September 28, 2020, 12:11:26 PM by Pete Svarrior »
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Re: An unedited clip of a weather balloon ascending to space, without fisheye.
« Reply #24 on: September 26, 2020, 09:21:06 AM »
It'll be a bit more complicated than that - to get any number for direct comparisons, we'll first need to establish which barrel distortion formula to use. This is one of the reasons why I'm advocating for a visual solution, rather than a numerical one.

Which barrel distortion formula? Can't you handle the algebra for arcs? It's given on the page for that sagittal calculator; any O-level schoolboy should be able to do the calculations.

I should be clear: I already have a good enough idea of the equipment used. That's what enables me to speak with a decent amount of confidence here...

Then please don't describe a lens as "bordering on fisheye" when it is anything but. A fisheye lens has a field of view of 180 degrees, more than twice that of an 18mm on APS-C.

I look forward to your own arbitrary arc drawing, since you had little difficulty with Regicide's screen captures:–

EDIT: For the absolute avoidance of doubt, here's your screenshot with the actual horizon traced correctly:

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Re: An unedited clip of a weather balloon ascending to space, without fisheye.
« Reply #25 on: September 26, 2020, 09:33:21 AM »
Which barrel distortion formula?
That depends on the specifics of the lens.

Can't you handle the algebra for arcs? It's given on the page for that sagittal calculator; any O-level schoolboy should be able to do the calculations.
I can "handle" it, just like I could "handle" your last proposed proportion. What I question is whether you chose to apply the right calculation. As I pointed out yesterday, these curves may or may not be arcs.

A fisheye lens has a field of view of 180 degrees, more than twice that of an 18mm on APS-C.
Again with the silly comparisons. Firstly, fish eye lenses start at 100° FOV. Secondly, the lens you propose this is is only a tiny bit away from a fish eye in terms of focal lengths.

You really try to force ratios where they don't belong. It does not inspire confidence.

I look forward to your own arbitrary arc drawing, since you had little difficulty with Regicide's screen captures
As I said, as soon as I have access to software that doesn't suck, I'll provide an appropriate illustration, like I did yesterday. I'm not sure why you'd complain about me not being at my desk right now, instead of just waiting a while.
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Re: An unedited clip of a weather balloon ascending to space, without fisheye.
« Reply #26 on: September 26, 2020, 09:52:49 AM »
fish eye lenses start at 100° FOV. Secondly, the lens you propose this is is only a tiny bit away from a fish eye in terms of focal lengths.

You really try to force ratios where they don't belong. It does not inspire confidence.

Really? Name an APS-C fisheye lens with a 100° field of view: not a rectilinear wideangle, a curvilinear lens. Then demonstrate how the video we're all discussing is shot using a fisheye lens.

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Re: An unedited clip of a weather balloon ascending to space, without fisheye.
« Reply #27 on: September 26, 2020, 10:02:52 AM »
Righto, here's where I'm getting 10px from:



It's difficult to see what's going on with the naked eye, but this curve follows through pixels which received the same amount of light at the time of shooting, thus likely representing a "true" horizon. It's a bit more intuitive when viewed at higher contrast:



Of course, the horizon is extremely blurry, so you may want to argue that we should follow one of the other well-defined lines that become visible at higher contrast. Using the second layer gives us a result that looks a bit more intuitive at low contrast.





That gives us a sagitta of 11px. So, yeah, "more akin to 10px" seems to pretty much get us there, but if you prefer I'll stick to "10-11px" :)

Really? Name an APS-C fisheye lens with a 100° field of view: not a rectilinear wideangle, a curvilinear lens.
Why would I do that?

EDIT: I'm still unsure what this achieves, but: Tokina AT-X 107 DX Fisheye @ 17mm f: https://tokinalens.com/product/at_x_107_dx_fisheye/

Then demonstrate how the video we're all discussing is shot using a fisheye lens.
Why would I demonstrate something that I patently don't believe, and which I actively argue against? The video being shot at a narrow angle only helps my case.
« Last Edit: September 26, 2020, 10:29:52 AM by Pete Svarrior »
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Re: An unedited clip of a weather balloon ascending to space, without fisheye.
« Reply #28 on: September 26, 2020, 10:06:24 AM »
Oh, while we're at it, let's verify your "3px" estimate for the tray. I'm not sure why I chose not to question it before, but...



In a truly shocking turn of events, it's actually 7px.

You might be starting to see where this is going.
« Last Edit: September 26, 2020, 10:30:55 AM by Pete Svarrior »
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Re: An unedited clip of a weather balloon ascending to space, without fisheye.
« Reply #29 on: September 26, 2020, 10:18:43 AM »
Since you refused to solve the problem visually, I will. Let's find out if Tiny Round Earth* holds any water.

First, let's ensure that we're only looking at arcs of identical** spans. I am discarding the sides of the image that we can't compare to the tray.



Now, let's trace the horizon.





Turns out the actual sagitta is 4-4.5px for an equivalent** span. A visual comparison also makes it plainly obvious that it is the tray that appears more curved. So, yes, the curvature of the horizon is much less pronounced than that of the tray. Tiny Round Earth* is not consistent with this observation.

You see the tray seam as "straight" because you expect it to be, and you see the horizon as "curved" because you really want it to be. However, at this altitude, and with such a narrow field of view, seeing any significant curvature should not be possible, and, unsurprisingly, is not possible.

Combine this with my rebuttal of Regicide's point: he was at the liberty to choose his own screenshots from multiple altitudes, and he ended up showing that the curvature decreases with altitude. This would not be consistent with the geometry of a sphere... unless we account for the optical effect you're so opposed to.

As always: when you follow a consistent and correct methodology, you get consistent results. Turns out that, despite your protestations, Tiny Round Earth* cannot be proved with this footage.

* - Remember, if you were correct here, the Earth would have to be round and much smaller than advertised. Regardless of FET vs RET, we can safely discard the "tiny" factor.
** - There is some room for inaccuracy here since our reference lines are at slightly different angles. Unfortunately, that's the experimental setup we were given. However, even with generous margins of error, there is no room for alternative conclusions.
« Last Edit: September 26, 2020, 10:51:17 AM by Pete Svarrior »
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Re: An unedited clip of a weather balloon ascending to space, without fisheye.
« Reply #30 on: September 26, 2020, 07:11:17 PM »
Righto, here's where I'm getting 10px from:



You pointed out inaccuracies in my version and Regicide's attempts to measure the horizon sagitta, so I expect you to apply the same standards to your own . Your purple straight line is not aligned with the left of the horizon. I measured from where the white area becomes pale blue at either side: yours goes from the middle of the pale blue at left to close to the transition at right. The "increased contrast" version I have been unable to reproduce by merely increasing contrast in my own bitmap editor, but if you can give me a link to the Bad Acid plug-in used I'd be obliged: I have an unrelated use for it in mind. For the purposes of this discussion it's useless and your result of 11 pixels invalid. Indeed, you're on shaky "Photoshopped" grounds there, see the wiki FAQ.


Oh, while we're at it, let's verify your "3px" estimate for the tray. I'm not sure why I chose not to question it before, but...



In a truly shocking turn of events, it's actually 7px.

Well, let's have a closer look again. My measurement was across a width of 715 pixels and I was very interested to see yours being across 776 pixels. Big deal, you may say, but I was very careful to avoid the curved area at either end of that seam, something you haven't done. At the left side especially, your measurement clearly strays into that curved area to the benefit of an increase in sagittal measurement. Tut, tut. I'm not saying you are being disingenuous, but both these measurements are sloppily done, so both are invalid.

Finally, you mention Tiny Round Earth, a term I'm unfamiliar with. I don't know whose tiny round head is supposed to have mentioned the subject, but it wasn't me, and I couldn't find it on the forums or the wiki. Could we have an explanation? With calculations for the result you claim?
« Last Edit: September 26, 2020, 07:13:32 PM by Longtitube »

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Re: An unedited clip of a weather balloon ascending to space, without fisheye.
« Reply #31 on: September 26, 2020, 07:45:00 PM »
Your purple straight line is not aligned with the left of the horizon
It is, and I showed you my methodology for why/how. If you dispute the methodology, it's on you to illustrate your objection. I used Photoshop, and reproduced the results in Corel. I'm not interested in your inability to adjust contrast in an image - honestly, if you can't perform such simple tasks, you probably shouldn't be getting involved in discussions that exceed your capabilities.

This, by the way, is why I keep suggesting that you use Lightroom. It's clear that all you can do is eyeball lines in MS Paint. You have an idiot-proof solution available to you. Use it.

Big deal, you may say
I may, and, indeed, if this is the best argument you have to offer, then I'll have to conclude you're no longer arguing in good faith - after all, if you had a sincere argument, you would have immediately followed up with a reasoned substsntiation. As a consequence, we're done here - I will not waste my time with someone who tries to lie his way through an inconvenient discussion.

I wish you the best of luck in arguing that the entirety of the Earth is roughly the size of the USA. In the meantime, the solution to your problem is plainly visible to all. You failed to analyse the images at every step of the process, starting with your inability to accurately trace the horizon, meausre heights, or even correctly apply proportions. There is nothing one can do to help a person who does not want to be helped.

If you wish to return to good-faith arguing, I will reconsider, but until then, this thread is now dead. Your failure has been illustrated, and you were not interested in rising up to the challenge. Fine by me.

(Of course, you may wish to defend your position by repeating the analysis over whatever width you find appropriate. Spoiler alert: you will not succeed at defending your Tiny Round Earth delusion.)

your measurement clearly strays into that curved area to the benefit of an increase in sagittal measurement. Tut, tut. I'm not saying you are being disingenuous, but both these measurements are sloppily done, so both are invalid.
I don't respesct liars, and you just showed yourself to be one.

If you're going to make a claim like this, substantiate it. Specifically, show the section of the image in which I "clearly stray into that curved area". Spoiler alert: you won't be able to, because I started my measurement at the very pixel the "curved area" ends. The quality of your work has been consistently atrocious. That's the crux here, really. Re-read through your failures. Note how you haven't been able to get a single technical detail correctly. Every measurement was wrong, every attempt at defining a proportion was wrong. You even challenged me to identify an example of one of the most abundant lenses out there. You know very little, and it's pretty obvious. And all that to defend a hypothesis that directly contradicts your worldview.

Feel free to restrict the image as much as you'd like and repeat the measurements. Here's a shocker: it won't suddenly make your Tiny Round Earth delusion true. No matter how far you run, you will not find a subsection in which your sloppy allegations work.

Have a fantastic day, TRE'er.
« Last Edit: September 26, 2020, 08:17:46 PM by Pete Svarrior »
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Re: An unedited clip of a weather balloon ascending to space, without fisheye.
« Reply #32 on: September 26, 2020, 08:21:12 PM »
I'll let the above images stand and let other readers judge for themselves.

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Re: An unedited clip of a weather balloon ascending to space, without fisheye.
« Reply #33 on: September 26, 2020, 08:24:32 PM »
I'll let the above images stand and let other readers judge for themselves.
Very well, if you ran out of couter-arguments, all I can do is rest my case and, once more, wish you a fantabulous day.

In the meantime, if anyone else wants to question my methodology or claim that the Earth is round and very small, you know where to find me. Longiboy's mantle is there for you to pick up!
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