Wednesday, February 22, 2006

attempt 2!

hammer!





Sand wedge!







I figured out that I've been exposing them far too long. These ones had shortened exposures so less ambient light was exposed and, in some instances, so there wasn't a second flash.





They got a little boring at this point, so these are just the detail shots.





Lessons:
- I either need to take shorter exposures or start doing this in a totally a dark area. I'm thinking of putting a 2x4 across my bathtub and doing this inside there with the door closed. Alternately I can start opening the f-stop a little further (i've been doing this at f11 for a decent depth of field).
- the flash keeps flashing twice; once on impact, and once again when whatever I hit lands (this is especially true in the sand wedge pictures). Solutions: either move the sensor further away or turn down the sensitivity.

The most important problem thusfar is the flash goes off at the very first instant of impact. this isn't necessarily the most interesting moment to be frozen. What I need is a way to delay the firing of the flash by tenths or ten thousanths of seconds before firing. This could be accomplished by soldering in a delay, which I could buy from the same place that I bought the flash from. This is unfortunate as it's another 20$ to throw at this project, with another 6$ yielding me a whole new sensor/delay setup (s/h is 6$ flat from this guy, so I can spend 18$ just getting a delay, or 25$ getting a delay and a new sensor). I'm tempted to do this and have 2 flashes going off at different times and from different angles but with different color filters on them (i.e. red at instant of impact, blue midway through explosion). I'm doing more research into doing this, the biggest problem being I have only 1 vivitar 283 (the easy to use flash for this project). I might wind up having to open up my other, smaller and cheaper flash and re-solder some connections to get it to flash for a shorter duration as well as for triggering remotely (as it lacks a PC cord). In other words, If I start this project from scratch, I'll be out 20$ and have a somewhat useless trigger stuffed into a tupperware container.

The alternative I thought would work when I bought it was moving the trigger further away, as the time it would take for the sound to reach it would create a minor delay.

So lets try some math:
Sound travels at around 700 miles an hour.
There are 5,280 feet in a mile.
700 x 5,280 = sound travels at 3,696,000 feet an hour.
Divide that by 60 (minutes in an hour) you get 616,000 feet a minute
Divide that by 60 again (seconds in a minute) you get a number around 1000.
Ok, so sound moves about 1000 feet a second. Meaning moving the sensor an extra foot away would take it another 1/1000 of a second to respond. I'm not sure I can move it any further than 5 feet and still have it work (it was at about 2 feet last night). Obviously more experimentation is required.

While all the above math might seem superfluous, it will come in handy for a later project that will involve much larger distances and incredibly loud sounds that will likely trigger the flash no matter how far away it is.

4 Comments:

Anonymous Anonymous said...

I really like seeing your process for making high-speed pictures, I think it is a great hobby.

Shameless plug here for the flash kit from O'Reilly: (I hope this is okay!)

There are a few challenges that the Quaketronics flash controller could help you with: Repeated flashes - it ensures that there is a few seconds dead time between flashes. Delay circuit - there is an adjustable electronic delay from 0 to .01 seconds. Two flashes with two delays - get two kits!

The flash kit from O'Reilly does cost more, and might not fit in a student budget.

-Tom from www.quaketronics.com

1:24 AM  
Blogger krylonultraflat said...

Haha shameless plug forgiven! Truth is, I didn't know about the MAKE flash until last week, long after I had bought the trigger I'm presently using. Had I known, I mighta gotten that one :) Remember, part of the reason I got the other trigger was that it was a 20$ investment, as I had inhereted (and coincidentally somewhat trashed) the 120$ flash that you were supposed to use with it. (although I figured out how to modify a 15$ flash to work with it as well. In all honesty, is it ok if I post that? I don't want to draw away business)

In reference to the disposable camera flash, is there a way to modify the duration of the flash coming from it?

Now that I know someone is actually looking, I'll post a picture of my entire set up later!

9:33 AM  
Anonymous Anonymous said...

No problem posting any new designs. The idea behind the kit and Make magazine is learning and having fun!

You can also use any of the circuits from our schematics, they are all online at Homemade Strobe Photography.

You can make a disposable camera flash faster by decreasing the size of the high-voltage flash capacitor. This will also make it less bright.

-Tom

1:00 PM  
Blogger krylonultraflat said...

Ahh the capicitor trick makes sense.
My next design involves using a 15$ Vivitar 2600 and soldering together the leads from the light sensor with the 25$ kit from the place I got my kit before. I'll likely post pics when the build is done.

I'm actually not all that good at building electronics. This is effectively my first soldering project, and I'm having so much fun with it that I hope it's not my last!

If all goes well, I'd like to also try my hand at building that circuit from your schematic next.

5:15 PM  

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