The View Up Here

Random scribblings about kites, photography, machining, and anything else

Even More Cowbell

Posted by Tom Benedict on 11/01/2015

I still haven’t used my new strobe gear to do portraiture. Which is kind of odd, now that I think about it, because that was one of the things I had in mind when I got it. I put some of this down to portraiture being a relatively new form of photography for me, so I’m not as driven to jump in. And some of it has to do with my only having one light and no reflectors. It’s tough to do good portraiture without at least a bounce card. (I know, I know… A bounce card is no more complicated than a piece of posterboard. I’ll get to that in a second.)

The real reason? NO ONE wants to be a subject, much less hold a piece of posterboard I tell them is actually a bounce card. (See? I told you I’d get to it!)

But that didn’t stop me from hoarding all the gift cards my family gave me for Christmas and using them to get  a second strobe, light stand, and umbrella. And it sure didn’t stop me from adding a 42″ reflector and flash diffuser to my cart while I was at it. As I placed the order I told Rydra that she and our little minions were now fair game. Oh yeah, baby! The portraits will roll! (Unfortunately, all of them know where I sleep, and know how to pull the batteries out of camera gear. So maybe this won’t work out as well as I’d hoped.)

Meanwhile I’ve been enjoying my single flash a great deal. No portraits, but I’ve been using it at work a ton. Most recently I’ve been using it while we’ve been investigating an issue on a much larger camera than anything I carry in my bag.

Megacam on CFHT

This is Megacam. When it was built it was the largest digital camera in the world. It’s a 320 megapixel focal plane fitted to a wide field corrector that’s optimized for use on our telescope. (And yeah, it came with Linux drivers.)

My real involvement with Megacam started as it was being integrated for use on the sky. Shortly after it saw first light, people figured out that it needed something that wasn’t part of the original design: a light baffle. That was my first large-scale project at the observatory: design and build a baffle for Megacam. The big black can on the bottom that looks like a silencer is what I came up with. It’s about 2m high and about 1.2m wide. To date it’s the largest lens hood I’ve designed and built. Tucked up above it is the wide field corrector assembly: four lenses and one image stabilizer (heck yes it includes image stabilization!) And it’s there that the story begins.

A few months ago one of our astronomers alerted us to what looked like a steady degradation in instrument performance. We investigated and found that the bottom-most lens in the corrector was dirty. One of the guys at work tried valiantly to clean it, but even his best efforts left the lens looking… ooky. To make a long story short, we took everything apart, looked at it through a microscope, and figured out what was going wrong. To our dismay we found that the optical coating on the lens was literally falling apart.

I wind up doing a lot of the documentation photography at work. Any time something goes wrong that we need a record of, I’m asked to pull out my camera and get busy. As part of the investigation of this lens I had the opportunity to do ambient light photography, dark-field photography, and (you guessed it) flash photography.

I needed a set of reflected light photos of the outer edge of the lens, but the room lights were killing me. So I turned them all off and pointed my flash at the ceiling to use as a giant white card. It worked great.

MC WFC L1 Acids

It’s not perfect. You can see the light fixtures in the reflection of the ceiling. But we’re not trying to do image analysis with these. The point was simply to record the state of the coating at several points around the edge of the lens. I couldn’t have pulled it off in the time I had available without my strobe.

I’m sure my second flash head will find its way into the photography I do at work. But what I’m really excited about is finally finally jumping into portraiture.

– Tom

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One Response to “Even More Cowbell”

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