Water drop HSS

[Robin_Usagani]

sorry dude.. my math is correct. I dont know what you are talking about. MY image above is barely cropped. I used a macro lens. I could have shot it closer but then depth of field will be a problem.

 

[Robin_Usagani]

gavjenks.. it is really hard to have this conversation with you. You edit your responses all the time. At one point you said your calc was wrong, then you edited it again.

 

[Gavjenks]

Sigh... I already explained why your math is wrong.
You did: velocity = gravity constant * time
The correct equation is: 1/2 * gravity constant * time.


And your image as displayed on the forum is 400 x 600 pixels = 240,000 pixels
Your Canon 5D is capable of producing 2912 x 4368 pixels = 12,719,616 pixels
Which means the image is only as large as 1.8% of the number of pixels your sensor is able to capture.

Last time I checked a 99.2% crop/scale is not "barely cropped"

 

[Gavjenks]

At one point you said your calc was wrong, then you edited it again.

Here's a double post for you instead of an edit then.

To be precise, I wrote that MAYBE you were right, because I found three websites with different equations, and none were very official. Then I went and looked it up in the physics textbook on my shelf, and confirmed that my initial formula was correct and yours was not. Then I edited my post again, because you weren't maybe right anymore.

In any case, it doesn't matter. The laws of physics do not warp depending on what I post on thephotoforum.com. It is absolutely v = 1/2 * g * t, and you forgot to divide by 2, or were using a bogus equation from somewhere.

 

[Gavjenks]

if you hadn't cropped and rescaled at all, then your image would be representing the entire sensor plane

The difference between your sensor's full length and the portion you showed here is a factor of 7x (along just one dimension, since motion is one dimensional)

Which means that capturing 6mph without motion blur at your current cropping is approximately equivalent to the difficulty of capturing 42mph without motion blur for an uncropped normal photo displayed at the same size on the screen as yours in the OP. For instance, one of a car.


Edit: Also, when you take a photo of a car, you would normally PAN the camera to follow it, which reduces its speed from 42mph to essentially just whatever your error is in hand shake and panning skill. Here, however, you cannot pan the camera to track the water drop. So you're at a major disadvantage compared to the car. You also cannot take advantage of horizontal tracking image stabilization in your lens. Taking all this into consideration, capturing 6mph at that cropping may actually be more difficult than capturing 100-200mph with no cropping + camera panning being possible.

 

[BlkdOutGsxr]

This is an odd thread to read... @OP I don't think that anyone is saying that you 'cannot stop motion' of a water drop well enough to photograph it using the technique that you mentions, but I think the point was that it's not the preferred or 'best' method of doing a shot like this. As for the nonsense over the calculations, I don't see what anyone is trying to accomplish by focusing on that part of the post; Whether it is 3mph or 6mph the OP's point was that he thinks even at 6mph he should be able to stop the motion of the water well enough for the effect he was trying to get. I'm not sure what the epeen battle is about beyond that.

 

[Gavjenks]

@OP I don't think that anyone is saying that you 'cannot stop motion' of a water drop well enough to photograph it using the technique that you mentions

That is exactly what I am saying, and I believe what Derrel was saying too.

At 6mph, I am claiming it is almost completely impossible to freeze the motion of a drop of water using only your camera shutter (up to 1/8000th of a second, assuming normal commercial grade cameras), if it is magnified to the size shown in the OP or in the original captain america water droplet thread.

At 1/8000th of a second, the 200 pixel image would still have upwards of 15-25 pixels of blur even under completely optimal and lucky conditions, which is still going to be completely obvious.

 

[BlkdOutGsxr]

@OP I don't think that anyone is saying that you 'cannot stop motion' of a water drop well enough to photograph it using the technique that you mentions

That is exactly what I am saying, and I believe what Derrel was saying too.

At 6mph, I am saying it is completely impossible to freeze the motion of a drop of water using only your camera shutter (up to 1/8000th of a second, assuming normal commercial grade cameras), if it is magnified to the size shown in the OP or in the original captain america water droplet thread.

I think what your arguing about is actually what you consider 'well enough to photograph it' was the point I was trying to make. Which I went on to say that I think you are trying to say there are better ways; ie closer to what you deem 'frozen'.

 

[Gavjenks]

Note that I am NOT saying it is impossible to capture ANY water drop with only your shutter.

For example, using only your shutter, you very well might be able to freeze the motion of any of the following:
1) A water drop that has just left the faucet and only fallen half an inch. This would be moving at 0.5 mph, not 6mph, and thus could be captured without noticeable blur.
2) A water droplet that was sprayed into the air and is photographed at the top of its trajectory, where it is almost completely still. You might even be able to capture the motion of such a drop with as slow as a 1/500th of a second shutter, depending on circumstances.
3) A water droplet in freefall along with the camera (for instance, in space, or if the camera and droplet are both inside of a plane that is taking a nose dive)
4) A water droplet in a vacuum, where size is not determined by air resistance, and where a drop can be much larger and thus require less magnification.
5) A water drop that takes up a much smaller portion of your final print. For example, if the photo is a picture of children playing in a sprinkler, and the droplet only takes up 2 pixels, then its blur would only be 0.2 pixels of blur, which wont even be rendered. The fact that it is much smaller in the final print makes it easier to freeze its motion even at higher speeds.
6) A water drop that is so predictable that the camera can be made to pan downward (for example using a computerized stepper motor) and track its movement. This would reduce the relative movement from the point of view of the camera, effectively making the droplet act as if it were moving slower. With perfect tracking, you could potentially freeze motion with 1/50th of a second...
7) Who knows how many other situations?

But this is not about any of those. This is about the situation at hand: a drop of water that has fallen 1.5m (6mph), and is being magnified to take up 200 pixels in the final image.

I think what your arguing about is actually what you consider 'well enough to photograph it' was the point I was trying to make. Which I went on to say that I think you are trying to say there are better ways; ie closer to what you deem 'frozen'.

Frozen simply means "few enough PIXELS of motion blur (in the case of a quantum, digital image) in the final, distributed version of the image that the viewer cannot notice the blur."

For most people, this is going to end up being maybe 2-4 pixels of blur, tops, for it to be seen as frozen. That simply cannot be achieved for the given situation using shutter speed alone.

 

[Gavjenks]

In case my explanation was unclear about why a photograph of a car is different:

In the image above, I applied some motion blur to the circles on the bottom. I then copied and pasted them at a smaller size into the upper image. Notice that the blur on the bottom is very visible, but the blur on the top is not. This is because on the top, the blur only takes up 1 maybe 2 pixels, and becomes pretty much invisible to the human eye, whereas 8 pixels or so of blur on the bottom is quite noticeable.

This is why magnification matters, and why a water droplet expanded to be the main subject of a photo is just as hard to photograph as a non-magnified or cropped car is even if it were traveling many times faster than the water droplet.

Pixels of blur in the final image is what matters, not speed in the real world. And pixels are based on relative magnification and relative speed to the film plane.

 

[Nahin]

I understand you promote such an stunning example, but relation btw calculation and figured. Actually couldn't perceive... :er:

 

[Robin_Usagani]

Gavjenks, you brought up good points, however:
1. My calc is correct. You got your formula wrong. Gravity Velocity Equations for Falling Objects by Ron Kurtus - Succeed in Understanding Physics: School for Champions

2. I only cropped a little bit to level. The size of water is like the size of a car in a frame when I shoot a car.

I told the OP of the other thread to kill the ambient light (which was the problem) or go to quicker shutter and hss. You are correct gavjenks about the cropping. You would need sharper stop motion if you had shot it with non macro which was something I didnt consider. In fact, when I made the point about hss, I assumed OP used a macro lens (the post was in macro section).

Thanks for having an intelligent conversation with me, that is exactly what I want.

 

[Robin_Usagani]

Gavjenks, i agree with you 100% about the pixel blur. But do you also agree with me if it was shot with macro, it would have been ok too? I think we were arguing different things. Major cropping was never in the original discussion. Derrel was simply saying I was wrong while photographers all over the world are going crazy over hyper sync (freezed by mechanical shutter). I see so many high speed action freezed by hyper sync. I was just making my point water drop is no difference. You could have done it with no flash out in the sun (macro).

 

[slow231]

At one point you said your calc was wrong, then you edited it again.

Here's a double post for you instead of an edit then.

To be precise, I wrote that MAYBE you were right, because I found three websites with different equations, and none were very official. Then I went and looked it up in the physics textbook on my shelf, and confirmed that my initial formula was correct and yours was not. Then I edited my post again, because you weren't maybe right anymore.

In any case, it doesn't matter. The laws of physics do not warp depending on what I post on thephotoforum.com. It is absolutely v = 1/2 * g * t, and you forgot to divide by 2, or were using a bogus equation from somewhere.

lol what? your final velocity is absolutely g*t (assuming you stat from rest). if you increase speed at a rate of 9.8 m/s-per-second, after 1 second you'll be going.... 9.8 m/s. if you just thought about it rather than blinding using a formula you'd realize this. your average velocity over that time period (again assuming you start from rest) would be half that though, and that's probably where your equation is coming from.

you can also look at his from an energy perspective. falling d distance gives a potential energy change of m*d*g, ending in kinetic energy is 1/2*m*v^2, so v=sqrt(2*d*g). and again robin is right.

i don't have much issue with you being wrong, it's more that you're adamant about something that you obviously don't have a very strong grasp of.

 

[o hey tyler]

ur feet secrete almost 1/4 a cup of sweat every day tell me that aint ****ed up