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01-15-2016, 08:19 PM - 3 Likes   #1
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Pixel Shift is FINICKY!

This morning we had a heavy frost here in northern Wisconsin.

I grabbed my Pentax K3ii and ran out and shot about 100 pixel shifted images of frosty trees.

There was very little wind. Basically just a very light breeze, certainly less than 5 mph.

Even this gentle breeze was enough to impact my pixel shifted images. Most of my images had a few magenta blotches and/or little areas of pixelation where a branch (or dead leaf) moved ever so slightly during the exposure.

Frankly, it wasn't that hard to clean up these pixel shifting artifacts in PhotoShop.

None-the-less, I've learned again that for landscape images one needs almost dead calm in order not to have pixel shifting artifacts in your images.


Last edited by Fenwoodian; 11-14-2016 at 08:49 PM.
01-15-2016, 08:27 PM   #2
osv
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looks like there is a bunch of detail in that shot, well done... and brrr! chilly
01-15-2016, 08:39 PM   #3
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I need to do some tests of merging N images with PS or Photomatix Pro vs. Pixel shift. I suspect in ideal conditions pixel shift will win. But in "real world" conditions that merging N photos together gets you 80% there and take care of "ghosting".

More later.

Michael
01-15-2016, 09:40 PM   #4
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I will have to wait for the new FF to get a go at establishing a working technique with pixel shift.

So whats often on my mind on this topic and your inputs will be most helpful :
1. Would you have got away with a pixel perfect shot using one frame if it was stopped down accordingly (likely f8, f11) at ISO100 and the shutter speed not being at all fast?
Especially so in the context of low light levels during sunrise, sunset hours, blue hour and use of ND filters.

2. How viable is it blending in parts that might be so 'corrupted' by pixel shift artifacts using one of the frames?

01-15-2016, 09:47 PM   #5
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The shutter speed does not have to be fast, but your setup needs to be stable, and wind has to be negligible. That's why pixel shifting is best for indoor applications.

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01-15-2016, 09:57 PM   #6
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My experience matches that of the OP. The scene was to almost dead still and the tripod has to be very stable for PS to be acceptable. The results can be spectacular if the stars align
01-15-2016, 10:12 PM   #7
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QuoteOriginally posted by pinholecam Quote
I will have to wait for the new FF to get a go at establishing a working technique with pixel shift.

So whats often on my mind on this topic and your inputs will be most helpful :
1. Would you have got away with a pixel perfect shot using one frame if it was stopped down accordingly (likely f8, f11) at ISO100 and the shutter speed not being at all fast?
Especially so in the context of low light levels during sunrise, sunset hours, blue hour and use of ND filters.

2. How viable is it blending in parts that might be so 'corrupted' by pixel shift artifacts using one of the frames?

There is no way to pull out one of the 4 frames to use in layers blending! I believe this to be an Internet myth that someone who never shot PS images made up.

It's a good idea, but to make it work one needs to take another shot that is not in the pixel shift mode.
01-16-2016, 02:32 AM   #8
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QuoteOriginally posted by Fenwoodian Quote
There is no way to pull out one of the 4 frames to use in layers blending! I believe this to be an Internet myth that someone who never shot PS images made up.

It's a good idea, but to make it work one needs to take another shot that is not in the pixel shift mode.

Thanks for the information.
Where I am, its mostly cityscapes rather than nature scapes, I might be able to get by the quirks providing I shoot that extra frame like you mentioned.
I do exposure, focus blending often enough anyway.



Its rather shocking to hear that there are no 4 frames "RAW" from the pixel shift.
It seems clearly explained in Imaging Resource's article on it
Pentax K-3 II Review: Now Shooting! - Field Test Part I
(nearer the end).

01-16-2016, 03:28 AM   #9
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QuoteOriginally posted by MJSfoto1956 Quote
I need to do some tests of merging N images with PS or Photomatix Pro vs. Pixel shift. I suspect in ideal conditions pixel shift will win. But in "real world" conditions that merging N photos together gets you 80% there and take care of "ghosting". More later. Michael
With stacking images you still have the issue of shutter induced vibrations or perfect alignment when aligned by software , even with mirror lock-up. I tried stacking N shots, and compared sharpness to a single shot, in the best case, sharpness is "almost" as good as for a single shot. A stacking mode with electronic shutter would be welcome. There's still a benefit of stacking N shots, the noise level / color resolution is a bit better than single shot, which allow more room for sharpening. Practically, with K-3+100 macro, I did a 100Mpixel panorama stitch of an array of 6 x 8 x stacks, the resulting image quality is such that 100% crop is just free of blur and free of noise.
01-16-2016, 03:45 AM   #10
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QuoteOriginally posted by Fenwoodian Quote
There is no way to pull out one of the 4 frames to use in layers blending! I believe this to be an Internet myth that someone who never shot PS images made up.

It's a good idea, but to make it work one needs to take another shot that is not in the pixel shift mode.
What about merging (even by hand) multiple pixel-shifted shots? I imagine that you'll get blur in the same areas, mostly (a loose leaf, tall grass etc., but have you tried that? just curious.
01-16-2016, 03:57 AM   #11
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QuoteOriginally posted by Fenwoodian Quote
There is no way to pull out one of the 4 frames to use in layers blending! I believe this to be an Internet myth that someone who never shot PS images made up.

It's a good idea, but to make it work one needs to take another shot that is not in the pixel shift mode.
I'm pretty sure that if you shoot RAW, the pixel shifted DNG that results does have four images within its container that can then be separated out. Not sure if you can only do this in Pentax Digital Utility that accompanies the camera or, if you can do it with Lightroom too. But my impression is that Lightroom can separate the images, but perhaps not process them together -- for that you need the Pentax Utility.

It would be a clunky process, but I suppose you could process the image once in the Pentax Utility to get a pixel shifted image, then split the RAW file and export one of the four images in the container and combine the two in Photoshop.

However, I don't own a K3 II, so this is just second hand information from the Forum.
01-16-2016, 04:02 AM   #12
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QuoteOriginally posted by Fenwoodian Quote
There is no way to pull out one of the 4 frames to use in layers blending! I believe this to be an Internet myth that someone who never shot PS images made up.

It's a good idea, but to make it work one needs to take another shot that is not in the pixel shift mode.
If you shoot raw with Pixel Shift, use the in-Camera-developing-Tool to convert it to a non pixel shifted JPEG. That's what the article says. The reason is because no third party developing tool can handle this kind of raw files till now. Maybe the Pentax utility came with the K3 can do it. Give it a run!
01-16-2016, 08:00 AM   #13
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QuoteOriginally posted by Fenwoodian Quote
This morning we had a heavy frost here in northern Wisconsin.

I grabbed my Pentax K3ii and ran out and shot about 100 pixel shifted images of frosty trees.

There was very little wind. Basically just a very light breeze, certainly less than 5 mph.

Even this gentle breeze was enough to impact my pixel shifted images. Most of my images had a few magenta blotches and/or little areas of pixelation where a branch (or dead leaf) moved ever so slightly during the exposure.

Frankly, it wasn't that hard to clean up these pixel shifting artifacts in PhotoShop.

None-the-less, I've learned again that for landscape images one needs almost dead calm in order not to have pixel shifting artifacts in your images.
Thank you for the post. It is very informative.

I had high hopes for PS. As Adam mentioned it is probably better for indoor applications. I shoot occasional studio stuff. With PS, I have to look at a continuous light set us as my strobe system will not work. I have done my share of landscape work. On of the iconic images of water scenes is the dragged shutter images. With PS, the water image, moving tree branches and any other moving subject is off the list. The promise of PS is great but the exceptions are too many, including your experience with slight wind and the subsequent camera movement. I almost swapped one of my K3s for a K3IIs but decided to wait for the FF to give PS a try.
01-16-2016, 08:57 AM - 1 Like   #14
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Third-party super resolution software is getting close to solving the moving objects problem apparent in pixel shifting. PhotoAcute, which has development for super resolution, noise reduction and HDR options, cliams to have solved it for HDR using something called "Precise Radiometric Alignment". When I tried to use it for Super Resolution however, some artifacts became visible where there were moving objects. But you can envisage an algorithm of the future that "super resolutes" parts of the images that dont move, while it simply "anti-ghosts" the parts of the images that contain moving objects. A kind of hyrid image, with some parts in high res and others in standard res, but should be a lot sharper overall than a single image. Using a camera that can shoot sequential images in rapid succession should help reduce percieved movement and therefore less artefacts in some cases.
Precise radiometric alignment.

Last edited by Scobra; 01-16-2016 at 11:17 AM.
01-16-2016, 11:36 AM   #15
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Scobra, Precise Radiometric Alignment certainly looks promising - thanks much for posting the link.

Wouldn't it be terrific if the new Pentax Full Frame had Precise Radiometric Alignment built in to its' pixel shifting algorithm!. Now that would be something that might win Pentax's full frame the "camera of the year" award for 2016.
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