When I upgraded from my Pentax K-5 DSLR to the K-1, I was intrigued by the new interval shooting options it provides. I do quite a bit of night sky photography so I was particularly interested in the Interval Composite Bright and Star Stream modes.
This video's introductory still image of star trails was shot with the Interval Composite Bright settings. This combines multiple exposures into a single image, retaining for each pixel only the brightest information for that point out of all the exposures. Of course, this can be done by combining individual exposures in software, which provides more flexibility and control than letting the camera create the composite image. I usually do strive for maximum control but I must say I am very happy with the out-of-camera result, which is a RAW file. The outcome might be less satisfactory if there was a problem with one or more of the exposures, such as a passing cloud or a spurious flash of bright light that likely would wash out dark areas of the final composite. Anyhow, this may be a lazy photographer's way of creating this kind of image, but without the disincentive of having to manage large numbers of image files and spend time on the computer assembling them, it makes the technique much more conveniently accessible and encourages just getting out there and doing it. The image consists of 90 30-second exposures; I had set the camera to record 150 exposures but I overestimated the amount of juice remaining in the battery and it ran out at this point. I am satisfied with the 50 minute composite (including pauses between each exposure) anyway.
I shot the Star Stream video later the same night. Star Stream is in its essence a time-lapse video version of Interval Composite Bright. From the descriptions I had read, I assumed it simply sequenced the progression of the composite to end on the same final composite image as the still imaging mode would produce. But wait ... what is that "fade" setting? The camera manual's instruction for the mode is sparse and I could not find anything on the internet (Has anyone else even tried this mode?) so I left fade in its default middle setting. Again, I was concerned that any clouds or other bright transients might ruin the whole video. I used the same exposure settings as I had settled on for the earlier star trails image, including the 30 second shutter speed. After starting exposure, I contemplated aborting to change to a shorter exposure time. In the bright moonlight I was using ISO 200 and the lens was not wide open, so with the excellent high ISO capabilities of the K-1 I could have gotten the shutter speed down to about 5 seconds without sacrificing much quality, but I left it alone. I went into my house and worked on my computer for the 2+ hours that the camera was recording. I looked out periodically but I never saw the clouds in that part of the sky or the aurora, which had been non-existent before that point in the night. So when I retrieved the camera and reviewed the video on the LCD, I was delightfully surprised by what I had captured and how well it worked. I had approached this as just a test to familiarize myself with the feature and the outcome was pure serendipity. Another surprise was that I ended up with 30 seconds of video from 240 exposures. The manual did not indicate frame rate but I had expected no more than 10 seconds at 24 fps. The video frame rate is indeed 24 fps, but it turns out that the camera triplicates each exposure so the effective frame rate really is only 8 fps. I guess the streaming effect smooths it enough that this is not really a problem. There are some artifacts, particularly noticeable in some of the transient clouds, and perhaps a faster shutter speed would improve that. The approximately 3 second gap between exposures also is an issue, more problematic at the 4K resolution at which I originally recorded this.
I am quite tickled with this Star Stream function. Granted, it is a rather singular effect that might quickly grow tedious with over-use. But it is unique enough to excite me as a new way of seeing the night sky. Could the effect be replicated in software using a set of individual time lapse images? I imagine so, and probably someone somewhere has done it ... I doubt that Pentax came up with the idea out of the blue. But surely that would be a complex and time consuming project. I am quite happy to let my camera do the drudge work, seeing as it does it so well. I surely will be playing with this function some more and trying different shutter speeds and fade settings.
Photographed with a Pentax K-1 and Rokinon 24mm f/1.4 lens; exposures of 30 sec @ f/2.2, ISO 200.
Video edited in Adobe Photoshop CC.
Created by John Reeve.
See more of my photography at http://www.jreeve.ca.