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06-24-2015, 11:33 AM   #1
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Pixel shift for landscapes

Hi all,
For those of you that have used pixel shifting in landscapes: do you find, on average, that it improves your shots or makes them worse? I understand it's use is dependent on shutter speed and subject movement (leaves, water, clouds), but in an average landscape do you find it useful? Do you have any pictures you could post of landscapes using pixel shift, for better and for worse?
Thank you!

06-24-2015, 11:59 AM   #2
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+1, particularly for long exposures using ND and/or those with moving water. The artifacts for short exposures are pretty well documented. I am interested in what happens with intentional blur.


Steve
06-24-2015, 12:32 PM   #3
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QuoteOriginally posted by stevebrot Quote
+1, particularly for long exposures using ND and/or those with moving water. The artifacts for short exposures are pretty well documented. I am interested in what happens with intentional blur.


Steve
I'll get you guys some samples soon. Moving water is going to be out of the question (you'll get fuzz in those areas because the camera won't correctly be able to calculate the color values). And if anything shifts during the actual exposure, even slightly, you can expect artifacts as well.

The pixel shifting feature is going to be beneficial for static subjects only (buildings, product photos, reproductions) based on what I've found so far.

Here's a building and a bunch of trees shot with a very light breeze and a shutter speed in the 1/180s - 1/250s range (can't remember exactly). Even then, see what happens to the trees:
https://www.pentaxforums.com/content/uploads/files/1/p1616/IMGP0026.JPG

Adam
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06-24-2015, 12:59 PM   #4
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QuoteOriginally posted by Adam Quote
Moving water is going to be out of the question (you'll get fuzz in those areas because the camera won't correctly be able to calculate the color values).
I was thinking exposures of about 1/10s to 2s for subjects similar to the below. Blur is anticipated/desired, but artifact (banding/blocking up) is what I am wondering about.


1s exposure



1/10s exposure


Super resolution and color tonality in the non-moving parts would be so very nice, though intuition says it will not work well. Very long exposures such as with ND 9 or ND 10 (several minutes) where blurring is complete might fare somewhat better.


Steve

06-24-2015, 01:01 PM   #5
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QuoteOriginally posted by stevebrot Quote
I was thinking exposures of about 1/10s to 2s for subjects similar to the below. Blur is anticipated/desired, but artifact (banding/blocking up) is what I am wondering about.


1s exposure



1/10s exposure


Intuition says it will not work well.


Steve
Or it could look so funky it starts a whole new type of photography.
06-24-2015, 01:41 PM   #6
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Can pixel shifted artifact be decreased/eliminated with faster shutter speed, say > 1/500?
BTW, beautiful shots Stevebrot!
06-24-2015, 02:08 PM   #7
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QuoteOriginally posted by seachongo Quote
Can pixel shifted artifact be decreased/eliminated with faster shutter speed, say > 1/500?
BTW, beautiful shots Stevebrot!
Unfortunately not. It's not the shutter speed that matters -- it's the interval between each of the four successive exposures. The camera needs to read the information off the sensor four times (well, three times between the first and last exposures) and that requires a fixed amount of time; subject movement during those in-between periods causes the artifacts.
06-24-2015, 02:25 PM   #8
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QuoteOriginally posted by Quicksand Quote
Unfortunately not. It's not the shutter speed that matters -- it's the interval between each of the four successive exposures.
But doesn't the camera have a pretty big/fast buffer? It should be able to take four 1/500 photos quite rapidly, no?
I would assume it depends on how fast the subject is moving, or rather how much it moves between frames.
or if it moves so much that you get total blur, then the shift should work okay, as well (As long as you get consistent blur, for example consistent water motion during each exposure)
Generally I would assume this has the same limitations as HDR bracketing. The images need to overlap nicely, and a certain amount of movement can cause differences

I am just theorizing, I would love to grab a camera and go take some tests in the local river valley, but I don't have a K-3II. If anyone is so curious they are willing to sponsor me

06-24-2015, 02:31 PM   #9
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QuoteOriginally posted by Na Horuk Quote
But doesn't the camera have a pretty big/fast buffer? It should be able to take four 1/500 photos quite rapidly, no?
IIRC the K-3 (II) limit of 8.3 FPS is driven by the sensor's readout data rate nearly as much as the mechanical aspects (mirror & shutter).

So even if you take the mechanical shutter and mirror out of the equation it's still going to take nearly 1/2 second to capture the four pixel-shifted exposures, irrespective of the shutter speed.
06-24-2015, 06:23 PM   #10
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PF user Tomtor here sent in a patch to dcraw that works with the K3II PS raw files. Not only can it merge the four files into a usable bitmap file (ppm by default), but it can also show artifacts (if any) generated during the PS process and also get rid of the artifacts in the bitmap. It is up on github here:

https://github.com/tomtor/dcrawps

Command line for now but I am sure a GUI will eventually be developed for it. I do not have a K3II but I have tried it on downloaded Pixel Shifted files and it seems to work as advertised.

Jack
06-25-2015, 12:56 PM   #11
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QuoteOriginally posted by jbinpg Quote
PF user Tomtor here sent in a patch to dcraw that works with the K3II PS raw files. Not only can it merge the four files into a usable bitmap file (ppm by default), but it can also show artifacts (if any) generated during the PS process and also get rid of the artifacts in the bitmap. It is up on github here:

https://github.com/tomtor/dcrawps

Command line for now but I am sure a GUI will eventually be developed for it. I do not have a K3II but I have tried it on downloaded Pixel Shifted files and it seems to work as advertised.

Jack
Very interesting! How would one implement this? Is it a patch for Pentax soiftware programming? Do the photos remain workable in post? Anyone willing to try this and report on results?
Thanks for posting this!
06-25-2015, 02:55 PM   #12
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QuoteOriginally posted by seachongo Quote
Can pixel shifted artifact be decreased/eliminated with faster shutter speed, say > 1/500?
No...

QuoteOriginally posted by Na Horuk Quote
But doesn't the camera have a pretty big/fast buffer? It should be able to take four 1/500 photos quite rapidly, no?
Doesn't work that way...

QuoteOriginally posted by Quicksand Quote
Unfortunately not. It's not the shutter speed that matters -- it's the interval between each of the four successive exposures.
We are getting close...

Pixel shift requires that the entire frame be exposed for the full period of time needed for all four exposures. The exposures themselves are done using an electronic shutter in the following sequence:
mirror up -->
first curtain drops -->
exposure one --> shift -->
exposure two --> shift -->
exposure three --> shift -->
exposure four -->
second curtain drops -->
mirror down
The fastest mechanical shutter speed at which the entire frame is exposed (first curtain fully dropped before second curtain starts its travel) is the X-sync speed of 1/180s (the minimum dwell for curtain movement). As a result, the effective shutter speed for stopping action is never faster than 1/180s + 4x the set exposure time + 3x the time to do a shift.

Example 1: Set shutter speed is 1/1000s for a pixel shift image
0.006 + 4(0.001) + 3(n) = 0.01 + 3(n) where n is the time to do the shift
The effective speed is a little longer than 1/100s.

Example 2: Set shutter speed is 1/10s for a pixel shift image
0.006 + 4(0.100) + 3(n) = 0.406 + 3(n)
The effective speed is a little longer than 1/2.46s


Steve

Last edited by stevebrot; 06-25-2015 at 03:04 PM.
06-25-2015, 03:25 PM   #13
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Really cool stuff. So there is no mirror action between each frame? What about slow shutter NR? Can pixel shift even be used with long exposures?
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