View Full Version : Pixel Shift and noise reduction

25-02-2016, 3:48pm
Hello All,
Here are some images from some test shots from today, made in an attempt to get a feel for the extent of noise reduction resulting from shooting in Pixel Shift mode.
Images shot with Pentax K-3 II
First shot (3870) f3.5, 1/13s, ISO 200
Second shot (3871) f3.5, 1/50s, ISO 800
Third shot (PS_normal_out) f3.5, 1/50s, ISO 800

I have selected a small portion of the shot that best visually shows differences in image quality due to noise, and taken a screen shot of all three images at pretty much the same magnification. The above images are in order left to right.


Not the most scientific process, but might help.


25-02-2016, 4:57pm
Looks quite OK. The Pixel Shift ISO800 is almost as clean as the ISO200 image, so the benefit is definitely there.

A few points tho:
1. Maybe be a bit more clear on the nomenclature you chose :p . The use of the term PS(ie. PS_normal_out) is obviously the Pixel Shifted image, but (as in the last discussion of such) maybe other's don't understand this.
I'm thinking PxS or something similar may be less confusing to those of us not acquainted with Pixel shifting .. ie. makes it harder to misinterpret or misconstrue it as reference to a PhotoShop term!

2. what software? And what format?(jpg, PEF, DNG) .. and does the chosen format in the camera make any difference to the test?
Also does the software used make any difference to the quality of the outcome?

That is, if you used Pentax's software to make the final PS image, is the final result as good as (or better, or worse) than say if you used Adobe software(ACR or LR or whatever)

Also curious if the advantage is linear? That is, as you shoot higher up the ISO chain, noise gets progressively worse. Does using pixel shift become more of an advantage at even higher ISO levels.

Another thing I recently noticed with the Olympus version of pixel shifting feature. It doesn't allow you to shoot past a pre determined ISO level(I think ISO1600 maybe? :confused013).
It's probably not really a problem as you really only use higher ISO's for the ability to shoot with smaller apertures or faster shutter speeds.
As the pixel shift feature is really only worthwhile on static subjects, those two issues aren't always a problem.
That doesn't mean that they never will be, just that they may not be in most situations(ie. landscapes/macros/etc).
Is the Pentax limited in any way with this feature .. can you shoot all the way up to max ISO?

anyhow... interesting info :th3:

25-02-2016, 5:29pm
Hello Arthur,
Re the nomenclature, I am trying to stick to the terminology that Pentax use, as I understand them. Sorry if it is confusing for people who think of PhotoShop or whatever, but I would rather use the Pentax terms than start inventing new terms that simply muddies the waters even more. I have defined what the images are, surely it isn't too hard for that to be understood and accepted.
Re the software. All images were shot in RAW (DNG) and conversion to tiff done using 'dcrawps' (a patched version of David Coffin's software). dcrawps was also used to convert/combine the 4 pixel shifted images into tiff. There was no other 'processing' done on these images. No in-camera noise reduction was used. What you see is roughly what the noise looks like prior to any post processing.
I haven't tested SOOC jpg, which is an option for a test of this sort.
I don't use the Pentax software for two reasons...firstly I don't like it, and secondly because I use Linux and it is only available for Windows and OSX. I do have it installed on Windows in a virtual machine, but only go there as a last resort which isn't too often.
I see if can get motivated into shooting at a range of ISO values to see how it scales.
I don't think there is any limit on ISO with the Pentax pixel shift mode.


26-02-2016, 2:06pm
I can now add a bit more to the story.
I have some test shots at 1600, 3200 and 6400 ISO, shot in normal mode and in Pixel Shift (PS) mode.
The camera settings were as follows;
Normal mode
IMGP3922.tiff 1/100, f10.0, ISO 1600
IMGP3923.tiff 1/160, f10.0, ISO 3200
IMGP3924.tiff 1/320, f10.0, ISO 6400

Pixel Shift mode
IMGP3925.tiff 1/60, f10.0, ISO 1600
IMGP3926.tiff 1/125, f10.0, ISO 3200
IMGP3927.tiff 1/250, f10.0, ISO 6400

As previously, I have screen shots with normal mode on left, PS mode on right to compare image noise.

ISO 1600

ISO 3200

ISO 6400

Again, as previously, all shot with Pentax K-3 II, saved in raw (DNG), converted to tiff using dcrawps. No post processing.


I @ M
26-02-2016, 2:29pm
That is impressive. :th3:

Particularly in the last pair of images, detail that was lost in the non shifted image, the creases to the left of the writing, are captured or "restored" nicely in the shifted pic.