High speed shots

[Lello]

Originally Posted by Canis Vulpes

Below is from the Nikon SB-800 manual, as can be seen reducing the flash duration reduces power.

1/1050 sec. at M1/1 (full) output
1/1100 sec. at M1/2 output
1/2700 sec. at M1/4 output
1/5900 sec. at M1/8 output
1/10900 sec. at M1/16 output
1/17800 sec. at M1/32 output
1/32300 sec. at M1/64 output
1/41600 sec. at M1/128 output

Thanks Stephen
Changing the power output does make a difference.

[Don Hoey]

Some great shots there Lello.

Superimposed shots are probably too long a flash duration. From Foxys post I would be aiming at using 1/128 output ( 1/41600 sec ) for maximum freezing of the action.
I guess the D300 is quite clean to allow setting 1600 ISO to allow for a reasonable aperture.

As for firing bb's or pellets then choose pellets. BB's are the more dangerous option as they are steel balls. Try for an air pistol rather than rifle as they are limited to 6 ft pounds which is half the power of an air-rifle.

Thinks .........................

I have an antique Webly air pistol. .............. try a bit of kitchen foil as a flash trigger ....... mmmmm . Another diversion ?????????

Don

[andy153]

Some great shots Lello and I have to say I admire all the enthusiasm BUT have you noticed one of the specs on one of the photo's - one millionth of a second exposure with strobe lighting - I know Nikon and Canon are good but I do not think any of our cameras can match that.

[Don Hoey]

Andy,
The key is flash duration NOT shutter speed. Camera on bulb in a dark room so the shutter is open. Even Stevies D100 can cope with that. As long as it is recognised that us mere mortals cannot get to flash durations greater than 1/50,000 sec then there are still lots of subjects that we can do. Rifle bullets cutting cards does require some pretty specialst kit in more ways than the flash dept alone though, I agree.
1 million/sec flash now that would be serious money.

Probably worth a mention on the flash front. Studio units are no good for this as you cannot get anywhere near the short burst duration that a decent camera flash on reduced power will give.

Don

[andy153]

Thanks for that Don - it's not a subject I've ever studied - makes sense though, do you need a very short, high intensity light for this then?

[Don Hoey]

Originally Posted by andy153

..... it's not a subject I've ever studied

Neither have I Andy. Never even truely tested top speed of 1/8,000 sec to freeze motion to understand its limitations.

Think of normal camera shutters and a series of blades ( 4 ) mechanically linked moving at 1/8,000 sec is no mean feat. To get that speed up to 1/30k or 1/50k to match the fastest burst from a flash requires a complete rethink of shutter design to reduce the number of moving parts.

Faster shutters are only of value if direct lighting is used. If flash is used then if exposure is for flash only, then flash duration becomes the key. Turning the power down does reduce the duration of the burst but also reduces the amount of light. That can be overcome by placing the flash closer to the subject.
Now you have two things affecting the overall exposure. Amount of light from the flash burst and ambient light recorded while the shutter is open. In a dark room with the shutter open there will be no ambient light so no image will be recorded. If you now fire a flash then an image will be recorded purely from the light generated by the flash. Flash duration will determine the ability of that burst of light to freeze motion.

In digital I guess the next consideration is amplification noise on long exposures. So a bit of experimentation is probably required here. For Lello's ballons then camera connected by a remote and you can probably get away with a few seconds. Trigger ... ( shutter open ) - Burst ballon ... ( flash fires ) - Shutter closes.

I have found a couple of further links that may be of interest.
http://chdk.wikia.com/wiki/Samples:_...r_&_Flash-Sync
http://www.woodselec.com/index.htm

Don

[miketoll]

I reckon the easiest (!) way would be in a darkened room with two synchronised flashguns set to lowest power for short duration of flash so would not have to have long exposure and noise worries. Without specialised equipment there will be a limit as to how fast an object could be 'frozen'. How about a dart? You would need just a little ambient light to see the target water filled balloon but with a fast shutter speed that would be irrelevant exposure wise.

[andy153]

Don, thanks for that and those links - very "illuminating" . I know Lello is using a sound trigger but somewhere I have an old Nikon ML-3 infra red remote unit - I think I'll try and set it up so whatever bursts the balloon etc passes through the IR as a trigger and I'll post what I get here. It should work for a dropped ball or hammer on water - lets see.

[Don Hoey]

You will be the death of me Lello, could not resist a go even though I do not have a sound trigger.

I dug out the air pistol and clamped it in my milling machine vice.
Pellet stop is a plastic bucket with 3 layers of 200mm rockwool roof insulation. Tests showed the pellet only just made it through one layer.

Without a sound trigger I thought to short out and so trigger the flash using kitchen foil. Two strips, one connected to each side of the old fashioned flash extension terminal.
NOTE IF YOU TRY THIS ........ depending on the trigger voltage of your flash you can get a bit of a shock if you close the contact with your fingers by accident. I did so I know.

I chose to use my old Vivitar 283 for this experiment. Trigger voltage is quite high but I could turn it down to give a flash duration of 1/30,000 sec.

First shot was to determine the distance the pellet would travel once it had triggered the flash. Triggering is by the pellet force closing the circuit between the two bits of foil.
As can be seen there is not much delay so I will have to work on that one for a pellet exiting the muzzle shot. Also 1/30,000 is not enough to freeze a pellet so it could be a case of exploding food shots.

Second shot was just to see that I could do it. First grape hit dead on but failed to trigger. Workbench and background suitably splattered. Second shot and time getting on so I made sure the flash would fire even though the foil would be visible in the end result. Bench even more of a mess now.

Exposure info : Camera on remote 2 secs at f16, ISO200, Flash duration 1/30,000 sec. - workshop lights off but enough daylight for me to see what I was doing.

Don

[Don Hoey]

Originally Posted by andy153

........ but somewhere I have an old Nikon ML-3 infra red remote unit - I think I'll try and set it up so whatever bursts the balloon etc passes through the IR as a trigger and I'll post what I get here. It should work for a dropped ball or hammer on water - lets see.

Neat Andy. Never seen one in the flesh so as to speak so I will see if I have any info in my Nikon leaflet collection.

Don