Sunday, February 26, 2006

how i got started taking these high speed photos

Two years ago, I bought a wealth of chocolate bunnies at local dollar stores and Ekerds around town. I had no idea what I was going to do with these bunnies, so I simply froze them and figured that eventually I'd use them for something that didn't involve eating.

One night my friend David came over to my apartment to meet me before we headed out for a drink. I have been known to force random friends to do random things, and David is usually my most willing target. This night was special, for it yielded the following: a firecracker placed in a frozen chocolate rabbit.



The gif is all the essential frames from the AVI my digital camera captured crammed together.

The last day of classes, when everyone was drunk at a neighboring apartment, I decided to try again, this time with a web camera that had a higher FPS than my digital camera did.

It took some doing, but it worked:


What I liked about both of these was that there was an instant in which they were spectacular. The first had a single frame in which purple cracks showed through the chocolate, immediately before flying into indiscernably tiny bits. The second exploded in sparks that momentarily held the shape of the rabbit before collapsing outward.

Rest assured come post easter, I am doing this again. Both with movies and with the expanded strobe set up I plan on having by then.

Friday, February 24, 2006

attempt 3!

I feel like I could do this a hundred thousand times and never feel I'd gotten it quite right. This is a good thing.



Notes:

Notes:
- This time on "odd photo experiments with john," we're throwing stuff into a bucket of water. The trigger would usually go off a) when the stuff accidentally hit the side of the bucket as i threw it in the dark b) when the stuff slammed the bottom of the bucket after making a big splash c) immediately upon touching the water.
- I went ahead and ordered another kit with a delay.
- ISO 800 is a no-no. Too much noise to be worth cropping.
- I cut out the internal light meter on my Vivitar 2600 and soldered the leads together, creating a short and shortening the flash. How does this work? danged if I know. Shorting the thyristor on the other flash worked, and it also worked here. It actually worked a little TOO well as now the flash is super short and weak. This is unfortunate as I don't want to get the flash too close and soak my gear.
- Ok I KIND OF know why it worked. The light meter was a piece of glass covering a photoresistor. My confusion stems from not having enough experience with the flash before cutting it up to know whether it flashed longer the more light hit it or shorter (i would guess longer, as I've removed ALL resistance and it flashes a very short time now)
- I didn't have a trigger for the 2600 and thus any double exposed below were a single flash with the sound triggered 283 (with a red filter) then a manual flash by the 2600 (no filter). Sometimes this came out right, oftentimes not.
- yeah that's a 7 inch i'm throwing. I picked one I knew I'd never listen to. Sorry The Hex, I'm not the only one who thinks that single sucks horribly (i got it on sale for 99 cents, realized it stunk, and later found a copy in the music directors closet of my old college radio station with a review that said "as hard as it is to believe Troubleman Records but out a bad release, this is shit.")
- a telephoto lens would be good. i should see if i can find a non-AF cheap telephoto lens that'll fit my camera on ebay.
- i think i'm going back to ice tomorrow. my bathroom is cramped.

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.

Tuesday, February 21, 2006

high speed photography rig

I assembled a high speed camera rig of sorts. Really its just sound trigger for a flash, soldered together and stuffed into a tupperware container. Leave shutter open on camera, make noise, flash goes off. What i'm actually most proud of is the fact that I managed to solder the thing together and a) not mess it up b) not burn the hell out of myself and c) incorporate an on/off switch that wasn't in the plans. You can see it in the pictures below. I bought the kit from here in the pre-soldered chip version that has since been discontinued.

Last friday night was kind of a test run and wasn't done in a dark enough place. Plus it was rainy and freezing, so not a whole lot was done. Later: bottles will be thrown or shot with slingshots or those crappy little pistol crossbows, and firecrackers will be stuffed into all manner of things. I kinda wish I had a backyard for this as opposed to a pool deck. I also need to start taking the pictures in RAW format so I can twiddle with the exposure more post taking the photo.
So far the results aren't as exciting as I would hope, but it's getting it at the instant of impact. I might later on add a delay to it so as it'll wait increments of 1/10,000 of second so as to not get things at their most speedy and blurry.

note: After reading the instructions for setting up my flash (half the reason i chose to do this project was that I owned the flash already and the chip and other components cost like 25$ total), I realized I was doing it wrong (namely, I needed to make a short in the thyristor to make it flash for as short as possible a time. i would never have figured out to do this on my own). The last picture is from an attempt done later on that had the flash at the right setting. Note that I found out that my flash, that I inherited from my family, is still made and costs 120$? I feel kinda bad putting stickers all over it now.

click on any of the below for an enlarged detail of the impact







(the flash unfortunately went off twice with this one)