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06-28-2015, 01:32 PM   #1
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K-3 ii Pixel shift of stars / night sky

Is this possible - K-3ii Pixel shift of stars / night sky?

-in-built astrotracer would be off (goes without saying!)
-wide angle lens
-static scene with stars/night sky
-a short exposure, but what exposure time can you do with PS?

has anyone tried this?

06-28-2015, 01:45 PM   #2
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the stars will move and you will likely get artifacts.
No different than any other moving thing.

Michael
06-28-2015, 01:52 PM   #3
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If the exposure time is short enough though the movement won't be a problem...

For instance I can shoot with no astrotracer [or other device], these settings and movement is not a problem/detectable:

f2.2
16mm
ISO 800
30 seconds

So pixel shift might be possible albeit at a drastically shorter exposure time (?)
06-28-2015, 02:07 PM   #4
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QuoteOriginally posted by Conqueror Quote
If the exposure time is short enough though the movement won't be a problem...

For instance I can shoot with no astrotracer [or other device], these settings and movement is not a problem/detectable:

f2.2
16mm
ISO 800
30 seconds

So pixel shift might be possible albeit at a drastically shorter exposure time (?)
You probably won't see much benefit, if any, but I suppose it would be worth testing for our review!


Adam
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06-28-2015, 02:13 PM   #5
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I have shot at 18mm f1.8 and the stars start to trail at 20 seconds. With Pixel Shifting enabled, you will get 4 frames at 30 seconds each, so it would essentially a 2 minute shot, and the stars would be trailing.

06-28-2015, 02:33 PM   #6
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QuoteOriginally posted by Adam Quote
I suppose it would be worth testing for our review!
Yeah that would be good!

QuoteOriginally posted by interested_observer Quote
I have shot at 18mm f1.8 and the stars start to trail at 20 seconds. With Pixel Shifting enabled, you will get 4 frames at 30 seconds each, so it would essentially a 2 minute shot, and the stars would be trailing.
How about 4x 2-to-5 second frames though... resulting in 8-to-20 seconds total (depending on what you choose)
06-28-2015, 03:06 PM   #7
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QuoteOriginally posted by Conqueror Quote
How about 4x 2-to-5 second frames though... resulting in 8-to-20 seconds total (depending on what you choose)
Since you are reducing your shutter time, you would need to increase your ISO to maintain the same exposure. This would increase your noise (going from ISO 800 to 3200).

The reasoning behind the pixel shift approach is to get more light to each pixel, thereby increasing the richness of the colors being captured. Stars really have no color. The colors that you are seeing in the various Milky Way shots are introduced by the photographer during post processing. The pixel shifting technology is not buying you anything when applied to astro.

You would be better off shooting at 20 seconds at ISO 3200, taking 4 frames and then stacking them using some astro software.

06-28-2015, 03:29 PM   #8
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K-3II manual page 87: pixel shift feature not available with astrotracer.
But there's also marked that Continuous shooting don't save raw data. Is this the only error?


Last edited by MartinsB; 06-28-2015 at 03:35 PM. Reason: added remark
06-28-2015, 06:22 PM   #9
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What if you use a star tracking camera mount like the IOptron?
06-29-2015, 05:05 AM   #10
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QuoteOriginally posted by interested_observer Quote
.......The colors that you are seeing in the various Milky Way shots are introduced by the photographer during post processing......
How do you mean "introduced by the photographer" ? Are the colours not already there and just exaggerated by post processing? Sorry for my ignorance
06-29-2015, 07:33 AM   #11
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QuoteOriginally posted by LennyBloke Quote
How do you mean "introduced by the photographer" ? Are the colours not already there and just exaggerated by post processing? Sorry for my ignorance
The best way to understand is to go out to YouTube and search for Milky Way. There are quite a few videos on post processing that show various ways of bringing out the MW, and then add some color in various areas.


---------- Post added 06-29-2015 at 07:38 AM ----------

QuoteOriginally posted by Not a Number Quote
What if you use a star tracking camera mount like the IOptron?
I think it will work much better, essentially the camera (pixel shifting) does not know that its moving. But, you are still taking 4 images in quick succession, with a slight movement to move the light to an adjoining pixel. It would probably be better just to have all the light going to the same area (pixel) and then stacking them. This is essentially additive, adding the light from all 4 images together. You should be able to do the same with pixel shifting, but they any pixel will have 1/4 the light, since you were moving from pixel to pixel across each of the images.

06-29-2015, 09:52 AM   #12
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Note that all stars do have an inherent spectral output and resultant colour. When they say that the Milky Way is white, what they mean is that over the millions of light years that the light from another galaxy must travel to reach us, what we are seeing is the sum of all the visible stars which adds up to white. So we are seeing the forest, not the trees. Our own Milky way stars are much closer so we do see their colour.
06-29-2015, 11:26 AM   #13
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QuoteOriginally posted by interested_observer Quote
Stars really have no color. The colors that you are seeing in the various Milky Way shots are introduced by the photographer during post processing.
Stars DO have color. The image pointed to by this Cloudy Nights sub-forum entry:

Milky Way from Colorado, East of Denver - DSLR & Digital Camera Astro Imaging & Processing - Cloudy Nights

shows Antares (bright orange star to the right of center) with its well-known orange hue, while Dschubba (NW of Antares, a 45 deg angle up and right from Antares) shows the contrasting blue. Many other stars are showing orangish or bluish, along with the many that do show as white. As well as showing color in MW shots, these stars show these same colors visually through a telescope.

Certainly these colors can easily be enhanced during PP, but these star colors are real, even in an unprocessed wide-angle camera shot.

Further examples can be found at:

DSLR & Digital Camera Astro Imaging & Processing - Cloudy Nights

and lots of DSLR astro-imaging information is available in this sub-forum and other Cloudy Nights sub-forums.

I find your statement misleading at best.

---------- Post added 06-29-15 at 10:28 AM ----------

QuoteOriginally posted by jbinpg Quote
Note that all stars do have an inherent spectral output and resultant colour. When they say that the Milky Way is white, what they mean is that over the millions of light years that the light from another galaxy must travel to reach us, what we are seeing is the sum of all the visible stars which adds up to white. So we are seeing the forest, not the trees. Our own Milky way stars are much closer so we do see their colour.
Correct.
06-29-2015, 01:24 PM   #14
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Stars have colors according to their temperature and spectral classification:

Star Classification - Zoom Astronomy

The hottest stars are blue, the coolest are red.

The Hertzsprung Russell Diagram
06-29-2015, 01:37 PM   #15
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QuoteOriginally posted by Conqueror Quote
If the exposure time is short enough though the movement won't be a problem...
Four exposures is four exposures. For your 30s example, the total time open would be a little over 2 minutes. The merged image at best would show a 2 minute star trail with a blip at each 30s mark.


Steve
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