Wednesday, October 08, 2008

K10D at 104,000ft

Earlier in the summer, a Pentax K10D was carried to the unbelievable height of 104,000ft to take some photos that would accompany a test of cosmic radiation at high altitudes done by the School of Mechanical and Aerospace Engineering at Oklahoma State University with the help of the NASA Oklahoma Space Grant Consortium. The K10D had a stock DA 18-55mm lens set to 18mm (manual focus at infinity), used Tv priority at 1/3000sec, Auto ISO (mostly ISO 100), and was set to capture Raw PEFs. The results were undeniably exciting photos from high in the stratosphere (19.7 miles).

All images in this post are copyright Dr. A. S. Arena Jr.

Dr. Andrew Arena Jr., the professor of engineering who organized the experiment, got a bit of attention for these photos (link to article at Imaging Info), even from Pentax USA president Ned Bunnell (link to his blog post), because the nature of the test required that the camera was relatively unmodified and it proved how reliable the K10D could be in very adverse conditions. Carried by a weather balloon into the near vacuum and extreme cold, the camera functioned as normal despite the circumstances. However, an unheated protection box with foam padding was built for the camera so that it would be safe enough to survive the +20mph impact on its return to earth by parachute, and a special timer was connected to trigger exposures every 15 seconds (seen below). Also, it's important to realize that it wasn't smooth sailing up and down; once the balloon burst due to low pressure, the payload would spin and bounce about, sometimes quite violently, until the denser air below was reached. The camera survived quite a thrill ride.

I had the pleasure of corresponding with Dr. Arena Jr. to ask him a few additional questions about the K10D rig they used for the experiment. Here's what he told me.

How long have you been taking pictures avidly?

I have been taking pictures for quite some time. My mom worked her way through college at a photography store, so I learned a lot about exposure, and lighting etc. from her. I got my first Pentax (the MX) and used it quite a bit for astrophotography in 1986 when comet Halley made its last visit. (Ed: he currently has a K10D, K20D, and still has his MX)

Why was the Pentax K10D chosen over other cameras for the project?

We had experimented with other brands in the past for the high-altitude experiments. They generally worked, but some had problems with temperatures, and none of the ones tested had the resolution and IQ we desired. For this flight we wanted the highest quality pictures possible, so it had to be at least a DSLR and an APS-C sized sensor. I chose the K10D due to my familiarity and experience with the Pentax brand and the K10D, the weather sealing, ruggedness, and the IQ.

The lens used was not sealed since the vacuum of space may have blown out the seals, but the camera gets so cold that a lot of condensation builds up on reentry. You can see that in the photos near landing. The outside of the camera was soaking wet after landing and so the weather sealing of the K10D is certainly a benefit.

Was the K10D used your own?

That particular K10D was mine that I “donated” for this test. After this successful test we will almost certainly buy one specifically for the project.

What was the wireless trigger device that you used to time the exposures every 15 seconds? Is it homebrew, or something off the shelf?

We have a homemade timer circuit, but we wanted to use something commercially made for this test. We used the Pclix LT 100.

Why did you choose shutter priority? As the balloon rotated and ascended, was it too risky to have a shutter speed that was too slow?

Exactly. There is quite a bit of motion in the balloon train especially going through atmospheric shear layers, and after balloon burst, so shutter priority is critical. From tests conducted on the ground it was decided that we wanted to assure a 1/3000s shutter speed. I was so impressed with the exposure metering of the K10D. We got over 500 pictures during the flight and only a handful of them were not useable due to exposure. The only ones where there was a problem is when the camera was aimed right at the sun. Of course aperture and ISO were adjusted automatically. The typical ISO was 100, and usually an aperture of about f/4.

Were there any other problems?

Everything worked beautifully, so there really isn’t anything critical that has to change [for the next time]. I don’t want to use a sealed lens because I am worried about the pressure build up in the camera blowing out the seals. The condensation we got that day was the worst case possible. It was a very warm and humid day so we had more condensation than we have ever seen. The only thing changing on the next flight is the lens. The kit lens was great, but now I want to try a prime out of curiosity. We are going to fly with the Pentax SMCP-DA 14mm f/2.8 next time. The only other thing I would change is to try the experiment with a K20D, but one thing at a time…

How long, in terms of minutes, was the K10D at an altitude high enough to be considered extraordinary by yourself?

The flight was 102 minutes, so I would say 102 minutes. The entire time the camera is bouncing around and swinging, and impacts at pretty high speed. Even though it is protected in the box for impact, I still think it is a challenging environment for a precision mechanical system. Here is the flight summary (link) if you want to see the altitude history.

I consider what you've done qualifies you as a "Pentaxian," do you feel like one?

Well I am certainly happy with all of my Pentax equipment, and continue to use it both at work and personally.

Dr. Andrew Arena Jr.'s Personal Pentax Gear List:

PENTAX DA* 50-135 f/2.8

PENTAX SMCP-FA 50mm f/1.4

PENTAX SMCP-DA 18-250mm f/3.5-6.3
PENTAX SMCP-DA 14mm f/2.8


TAMRON AF 90mm f/2.8 Di SP macro
TAMRON SP AF 17-50mm f/2.8 XR Di-II



References: Special thanks to Alysha Sideman at Imaging Info for her excellent article.


Olivier said...

Thanks for this very interesting interview.

Abdel Castro Pérpuli said...
This comment has been removed by the author.
Abdel Castro Pérpuli said...

Congratulations on the photographs, they are awesome!

After reading this I feel even better about the decistion of buying a Pentax as my first SLR.

how to take professional pictures said...

Practice until you know all the major buttons and settings without having to actually look at what your fingers are doing.Sometimes the perfect shot only lasts for a second or two,and you don’t want to miss that quick little grin because your fingers were trying to fumble with unfamiliar settings.Such a great information.

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