Water drop HSS

[Robin_Usagani]

This is in response to this thread. If you pay attention in your physic class in HS or college, you should be able to follow my calculation.
http://www.thephotoforum.com/forum/macro-photography/326634-captain-america-water-drops.html

Now let's just assume we are not using a flash. Is derrel really saying you cant use the mechanical shutter to stop the motion of the water that is only 5.48 miles/hour? Give me a break. Of course you can use HSS to stop a water drop. It is not going that fast. If you are talking about a spinning tool, then of course HSS or ambient light is not going to cut it (High Speed Shutter vs. Ordinary Flash Sync). Usain Bolt average velocity is 23.4 mph. Is derrel really saying you can't stop motion of Usain Bolt? Fire away. I am just really sick of getting picked by derrel. I understand derrel is full of knowledge but he is not right all the time. Let the flaming begin. I was going to set up off camera HSS to shoot waterdrop to proof it (with tripod, constant drip, constant focus point), but I figured a simple physic calculation should do it.

 

[Derrel]

Here are a few I just did. Hand held, focus was all over the place, HSS, shutter was 1/2000 or faster. Unfortunately since this is handheld, I had to burst the shot so I had to lower the flash power so I can fire it consecutively. Because of that I had to bump up the ISO. If I had used a tripod and keep adjusting the focus, I can probably shoot it at lower ISO and get better timed shots. I have no idea what derrel is talking about.

View attachment 44292

Blurry. Not round. Shows motion blur, as I predicted it would.

View attachment 44293

Blurry. Sorry Robin, just as I predicted.

View attachment 44294

In your last picture you show us a nice stroboscopic effect, but it does not stop or freeze the motion...just as I said it would not. HSS is a series of very rapid flash micro-bursts, up to 199 flashes per second, according to the Canon website. You can see here that no motion has been "stopped", or frozen. Exactly as I stated. I can see 15 discrete background images here...this water is not frozen, as you stated it would be using HSS. It is rendered exactly as I predicted...a series of very,very rapidly-paced micro-flashes were emitted, turning this into over an inch-long rendering. "stroboscopic rendering"

You calling me an ass in the Captain America Water Drops thread, as well as your beginning of this new, separate thread with some calculations, but none of these blurred photos to support your calculations...just wow Robin, all in all weak sauce.

Your photos above proved that I was right, and you were incorrect. Sorry, but your very own photos demonstrate that your technical knowledge and understanding of Canon HSS flash is faulty.

HSS flash is sequential, micro-burst flashes that a fired over a relatively looooooong duration, in order to make the flash last for the entire duration the mechanical focal plane shutter is traversing the film plane.

What a person wants to do in trying to render high-speed motion utterly stopped, as in frozen, is to use a SINGLE, very brief-duration flash. This is normally accomplished by using AUTO-thyristor flash, fired at low fractional power, usually between 1/16 and 1/128 power, which fires a very short,duration flash of as brief as perhaps 1/64,000 second. Your first two, blurry images prove that I was correct, and you are not fully aware of how HSS actually works, in the real world.

 

[Robin_Usagani]

Here you go derrel.. I shot a few more just for you. I use tripod this time. Are you really saying I cant stop an object that is going 6 mph with my shutter? Give me a break.

 

[Ballistics]

So... did you find out whose is bigger yet?

 

[Robin_Usagani]

gosh.. the exif is stripped.. not sure why.. brb.

 

[Robin_Usagani]

So... did you find out whose is bigger yet?

Only one way to find out.

 

[Gavjenks]

This is solvable by math, but you didn't do enough of it to arrive at a conclusion.

Size a water drop can be while still circular = roughly 2mm
Number of pixels in diameter the guy wanted a drop to take up for the captain america thing = roughly 200 pixels (see the printed dimensions of the shots compared to drop size)
Amount that the drop can move in frame during the exposure to see essentially ZERO blur = Maybe a few pixels. 3-4? Subjective, but that's already pushing it.

Thus, the distance in real life that the drop can fall during exposure to see no blur at best = 4 pixels / 200 pixels = 2% of its diameter = 0.04 millimeters

At 1,223 mm/s fall speed (your math was wrong for 1 foot of fall), the time it would take to fall 0.04 millimeters = about 1/30,000th of a second





However, why on earth would you wait for the drop to fall a full FOOT before photographing it? that's just making your life much harder. The drops break into individual spheres much much earlier than that if you set it up right. In the linked photos above, you can see pretty round drops in less than an inch of fall (after many shots, you should be able to luck out and get one nearly perfect). This would yield a velocity of 0.353 m/s instead.

Which yields a required exposure of about 1/8500th of a second.




Conclusion: HSS should just BAAAAARELY be capable of getting the image with less than a few pixels of motion blur by using a higher end camera body capable of 1/8000th shutter speeds. But everything would have to be just right, and still, you're really pushing it... if you try to make the drop too big in frame people will absolutely notice blur. Even just 200 pixels like in the captain america example may be too large.

You are much better off by doing the following, which doesn't even require any additional equipment to be bought (assuming you were using flash to go at full HSS previously):
1) Set up your normal professional quality (e.g. nikon or canon modern) speedlight
2) Set it at its lowest power (1/64th or 1/128th or whatever). lower power yields shorter flash durations.
3) Set up in a dark room, with almost no ambient light.
4) Have focus manual and pre-adjusted, obviously.
5) Fire at a shutter speed of 1/200th or 1/250th of a second or however fast you can go on your camera JUST BEFORE HSS flash turns on (the max speed of your shutter without requiring both leaves of the shutter to be in motion at once) something (so that HSS does not engage). You may need to look up what this threshold is for your camera body.

Using for example a typical Nikon SB-800, set at 1/128th power, the duration of the flash is a blistering 1/41,600th of a second. Since you have no ambient light, none of the rest of the exposure matters, and you can capture the water drop without even a single pixel of blur at 1 inch of fall.

Vastly superior than trying to use HSS flash at your camera's max shutter speed.

 

[Gavjenks]

Here you go derrel.. I shot a few more just for you. I use tripod this time. Are you really saying I cant stop an object that is going 6 mph with my shutter? Give me a break.

You're not following your own requirements, dude. That drop in the photo is OBVIOUSLY not a foot below the point of being dropped. it looks closer to about half an inch to me. So it's not going anywhere close to 6 miles per hour. more like 0.5 miles per hour. (Note that even at 1 foot, it isn't going 6 miles per hour, because you did your math wrong. A drop at 1 foot = about 3 miles per hour.)

Also, your drop is not circular, and it's even smaller than the captain America ones (yours is 170 pixels top to bottom). Smaller images on the sensor make it easier to capture without noticeable blur, so this is also cheating.



What you have proven is that at 1/6400th of a second, you can capture a drop (charitably speaking -- it is very wobbly) that is smaller than the original thread's drop, and is only going 0.5 miles per hour.

You still have 5.5 miles per hour and another 30 pixels in diameter in the image to go to prove your point.

 

[Robin_Usagani]

Where did I mess up my calc Gavjenks? I checked everything. You are right, it can be shot sooner than 1 ft (even slower velocity). It was just an assumption. I understand that the best scenario is to use zero ambient and go with smaller power (shorter tail), I never denied that. What I am trying to prove is that it really isnt going that fast. I still think at 1 ft it is at 2.45 m/s (2450 mm/s).

This is solvable by math, but you didn't do enough of it to arrive at a conclusion.

Size a water drop can be while still circular = roughly 2mm
Number of pixels in diameter the guy wanted a drop to take up for the captain america thing = roughly 200 pixels (see the printed dimensions of the shots compared to drop size)
Amount that the drop can move in frame during the exposure to see essentially ZERO blur = Maybe a few pixels. 3-4? Subjective, but that's already pushing it.

Thus, the distance in real life that the drop can fall during exposure to see no blur at best = 4 pixels / 200 pixels = 2% of its diameter = 0.04 millimeters

At 1,223 mm/s fall speed (your math was wrong for 1 foot of fall), the time it would take to fall 0.04 millimeters = about 1/30,000th of a second





However, why on earth would you wait for the drop to fall a full FOOT before photographing it? that's just making your life much harder. The drops break into individual spheres much much earlier than that if you set it up right. In the linked photos above, you can see pretty round drops in less than an inch of fall (after many shots, you should be able to luck out and get one nearly perfect). This would yield a velocity of 0.353 m/s instead.

Which yields a required exposure of about 1/8500th of a second.




Conclusion: HSS should just BAAAAARELY be capable of getting the image with less than a few pixels of motion blur by using a higher end camera body capable of 1/8000th shutter speeds. But everything would have to be just right, and still, you're really pushing it... if you try to make the drop too big in frame people will start to notice blur.

You are much better off by doing the following, which doesn't even require any additional equipment to be bought:
1) Set up your normal professional quality (e.g. nikon or canon modern) speedlight
2) Set it at its lowest power (1/64th or 1/128th or whatever). lower power yields shorter flash durations.
3) Set up in a dark room, with almost no ambient light.
4) Have focus manual and pre-adjusted, obviously.
5) Fire at a shutter speed of 1/200th or 1/250th of a second or however fast you can go on your camera JUST BEFORE HSS flash turns on (the max speed of your shutter without requiring both leaves of the shutter to be in motion at once) something (so that HSS does not engage). You may need to look up what this threshold is for your camera body.

Using for example a typical Nikon SB-800, set at 1/128th power, the duration of the flash is a blistering 1/41,600th of a second. Since you have no ambient light, none of the rest of the exposure matters, and you can capture the water drop without even a single pixel of blur.

 

[Robin_Usagani]

gavjenks, i will use a cup with a hole next time. I used a faucet and it made the drip looked a little weird.

 

[Gavjenks]

I assume you miscalculated time. I don't really want to worry about how, because you never even needed to calculate time in the first place, when you can just use the equation for velocity directly from displacement:

V = sqrt(2 * g * d) / 2
V = sqrt(2 * -9.8 * 0.305) / 2
V = sqrt(-5.978) / 2
V = 1.223

Edit: It was your velocity from time equation. V = 1/2 * g * t. Left out the 1/2

 

[Gavjenks]

gavjenks, i will use a cup with a hole next time. I used a faucet and it made the drip looked a little weird.

But you also need to make it actually fall an entire 1.5 meters before photographing it (distance it takes to get to 6 miles per hour), instead of what looks to be about half an inch in your photo, if you want to prove your point that your shutter can capture an object at 6 mph at that level of magnification.

 

[Robin_Usagani]

i didnt leave it out. it is d=1/2 g t^2 . I am confident with my calc. It is stuck in my head since HS.

 

[Robin_Usagani]

gavjenks, i will use a cup with a hole next time. I used a faucet and it made the drip looked a little weird.

But you also need to make it actually fall an entire 1.5 meters before photographing it (time it takes to get to 6 miles per hour), instead of what looks to be about half an inch in your photo, if you want to prove your point that your shutter can capture an object at 6 mph at that level of magnification.

1.5 meters?? It is going 5.48 miles per hour at .305 meter! Is it really that hard to get a sharp photo of a car going 5.5 miles/hour? No.

 

[Gavjenks]

gavjenks, i will use a cup with a hole next time. I used a faucet and it made the drip looked a little weird.

1.5 meters?? It is going 5.48 miles per hour at .305 meter! Is it really that hard to get a sharp photo of a car going 5.5 miles/hour? No.

But you also need to make it actually fall an entire 1.5 meters before photographing it (time it takes to get to 6 miles per hour), instead of what looks to be about half an inch in your photo, if you want to prove your point that your shutter can capture an object at 6 mph at that level of magnification.

No... as I just pointed out above, your math was wrong, and at 0.305 meters, it is going 2.74 mph

At 1.5 meters, it is going 6.1 mph.



And the car is completely different. You normally would take a photograph of a car with your entire frame, and then you'd put the entire frame onto your final print.
Here, however, you are taking a 200 pixel wide drop and magnifying the image to the point where only 2% of your sensor is showing up on the final print (above, your images are 400x600, and your camera can do 3,000x4,300). This makes motion blur extremely more visible at slower speeds.

It's the equivalent of something going 40-50 miles per hour at normal magnification (print uses your full frame)... without you tracking it.