Ed Nisley's Blog: Shop notes, electronics, firmware, machinery, 3D printing, laser cuttery, and curiosities. Contents: 100% human thinking, 0% AI slop.
So we did the HersheyPark thing on the way back from our bicycling vacation and our young lady rode seven of their eleven roller coasters. Not being all that strong of stomach, I wimped out after two and contented myself with taking pictures.
I had decided to not lug a Big Camera and the tele-adapter along, seeing as how we’d be camping for four nights. That turned out to be a wise decision: it rained every night and everything we carried was damp. So I took pix with my Casio Z-850 pocket camera, which had been sealed in a ziplock bag most of the time, and that had to be good enough.
The Fahrenheit coaster is, they tell me, 121 feet tall and I was standing outside the fence about 100 feet from the base of the drop; the slant range was maybe 150 feet. I had plenty of time to set up and practice the shot, as the line was half an hour long. I filled the equivalent of two rolls of film with pix of people I don’t know while exploring a nine-dimensional parameter space & scrutinizing the results; pixels are cheap.
Most digital cameras, this one included, have a long delay between pushing the button and getting results. However, it has several “continuous shutter” modes and I picked the “high-speed” version that records three images in quick succession. There’s no indication of how much time passes between exposures, which probably depends more on the SD Card’s speed than anything else. The timestamp resolution is 1 second, which isn’t much help.
Anyhow, poking the shutter button when the train came over the top consistently produced one good picture as it descended.
Continuous Shutter Images
I fought all the other automation to a standstill:
Infinity focus
Shutter speed 1/1000 sec
Aperture f/5.1
The camera picked ISO 200, probably as a result of the “high speed” continuous shutter setting, and warned me that it wasn’t happy about doing that. This being a bright, sunlit day, the nominal exposure for that ISO speed would be 1/200 @ f/16. Two stops faster shutter and three stops bigger aperture should work out OK, as the subjects were on the down-sun side of the coaster. The camera has just two apertures (big and little) that, of course, vary with the zoom setting, so I didn’t have much leeway. I figured I could fix any minor exposure issues in the cough darkroom.
The tele end of the zoom range is equivalent to a 114 mm lens with 35 mm film, which is better than the beer-can-sized zoom on the SLR I used to lug around back in the day.
In round numbers:
the car is 30 feet long and the original image is two cars tall, call it 60 feet
the image is 2816 pixels tall
(60 * 12) / 2800 = maybe 1/4″ per pixel
Cropping the interesting part from the frame, goosing the gamma a smidge, and applying a touch of Unsharp Mask says that’s about right: you can see the expressions on their grainy little faces. National Geographic quality, it ain’t, but it’s OK for a pocket camera and pix of relatives.
Memo to Self: Would forcing the ISO down to 100 reduce the graininess a bit?
It’s that time of the year again: a pair of hens and about a dozen chicks have been cruising through the yard. The chicks vary from softball- to football-sized, so we think the hens are tending a creche.
The chicks are, of course, insufferably cute…
We haven’t seen a hen with chicks roosting in the trees this year, but that just means they’re using trees near the creek rather than ones we can see from the house.
Tom Turkey Closeup
That cute thing the chicks have going for them tapers off pretty quickly as they grow up.
Wow, are those big toms ugly!
But it works well enough for turkeys, so who are we to complain?
Watching the tree frogs crawl up the tent from inside let us see how they move: hand-over-hand up the fabric. A dozen of them crawling along was spooky…
I took a movie with my pocket camera that turned into an 8 MB AVI, which I can’t upload here. Most of it isn’t all that interesting, anyway, an observation which hasn’t stopped YouTube dead in its tracks yet, but we can do better than that.
A pair of Free Software programs extracts the interesting part and produces a (somewhat) smaller animated GIF that works with WordPress.
A bit of browsing showed that I wanted frames 227 through 265 and that the frog was pretty much in the upper-middle of the image. So, crop a 320×240 image around the frog from those 640×480 frames:
cd frames
mkdir stills
for f in `seq 227 265` ; do convert frame-$f.jpg -crop 320x240+160+60 stills/still-$f.jpg ; done
Then convert them into an animated GIF with a 500-ms frame rate (the -delay ticker is 10 ms):
cd stills
convert -delay 50 still-2* frogwalk.gif
It’s a 1.6 MB wad, but gets the message across: frogs keep three paws stuck to the floor.
Remember, that little guy is moving at glacial speed in the GIF: those 40 frames of video last just over a second in real time.
Memo to self: MPEG-1 and MPEG-2 only support video-style frame rates around 30 fps.
Update: Regular reader Przemek Klosowski showed me how to generate those numeric sequences on the fly, without using a for loop:
There's this neat Bash construct {1..10} that you can use directly after ffmpeg:
convert -delay 50 still-{227..430}* result.gif
You can even skip every nth frame:
convert -delay 50 still-{227..430..5}* result.gif
We bicycled along the Pine Creek Gorge rail-trail in north-central Pennsylvania on a Rails-to-Trails Conservancy group ride, camping at schools and campgrounds along the trail. Quick summary: for four days we rode in the sun and slept in the rain.
Tree Frog – Natural Light
As we set up camp at Pettecote Junction, the wet ground was hopping with tiny tree frogs. It was impossible to avoid stepping on the critters. When we got the tent set up, they swarmed up the sides between the tent and the rain fly; perhaps they had an imperative to get above the flood?
The lines in the tent fabric are about 3.7 mm apart, so the frogs are perhaps 10 mm from snout to butt. That size rules out everything in our RTP Eastern Reptiles & Amphibians book except the Little Grass Frog, which used to live only south of Virginia. The spot pattern doesn’t match, either, although they’re said to be highly variable. Who knows what’s going on in these degenerate days?
Tree Frog – Flash Illumination
They didn’t like the mesh vent screens, favored the rougher tent fabric over the smoother seam binding, and didn’t seem to mind falling off the tent.
Some years ago a friend brought a favorite old camera that he’d just rediscovered. As you might expect, the exposure meter battery had long since died and its lid was rust-welded in place. Alas, he’d tried and failed to remove the lid by applying, mmmm, inappropriate tools to the coin slot.
I proposed building a quick-and-dirty pin wrench from an aluminum knob, which requires a matching pair of holes in the lid. Given that the lid was already pretty well pooched, he had no objection.
IIRC, I laid a strip of masking tape over the lid, laid out the holes perpendicular to the slot, then drilled them out by eyeball. The trick is to avoid drilling into the battery; it’s likely all dried out by now, but there’s no reason to release any more of that glop than absolutely necessary.
Battery cover wrench
Then I turned the threaded boss off the bottom of the knob and drilled two slightly larger holes separated by the same distance. This would be ideal for manual CNC, but I didn’t have the Sherline at the time, difficult though that may be to imagine.
When you can’t do precision work, epoxy is your friend.
Lay new tape over the battery lid
Cut two lengths of music wire with a diameter to match the holes in the battery lid using a Dremel abrasive cutoff wheel
Stuff the wire stubs into the holes, wipe off excess epoxy
Jam the pins through the tape into the holes in the battery lid
Wait for a few minutes…
You can see the top pin is slightly offset in its hole, but the epoxy ensures that the pins are an exact fit to the lid. The tape prevents the wrench from becoming one with the battery lid. Not drilling into the battery means the pins bottom out on the battery. Music wire means the pins won’t bend; copper wire doesn’t work in this application.
If you’re good with the Dremel, the pins will be not only the same length, but the proper length. IIRC, I made them a bit long and then trimmed them to fit.
Battery lid removed
When the epoxy cures:
Remove the wrench
Remove the tape
Install the wrench
Twist the lid right off.
Works like a champ!
Much to our surprise, the inside of the battery compartment wasn’t a mass of corrosion and the threads were actually in pretty good shape, all things considered. It’s not clear why the lid was so corroded, but there you have it.
He went home happy… taking the wrench along, although we hope it’ll never be used again.
(I found these pix while I was looking for something else. My close-up technique has improved over the years: a tripod, bright lights, and the smallest possible aperture are my friends.)
The Smell of Molten Projects in the Morning 