New 2.2 version of iWE RAW Editor (HHHR is added)

Started 1 month ago | Discussions thread
Anders W
Anders W Forum Pro • Posts: 22,144
Re: A note on slow rolling shutters and merging...

kenw wrote:

First of all, very impressive work!

Second, something to be aware of is the potential for a slow rolling shutter on a high resolution camera to cause alignment issues across the frame.

I did some experiments with multiple exposure super-resolution on a Nikon Z7 (45MP) in full sun hand held (Photoshop stacking, not iWE). When shooting with the fully electronic shutter (1/16 sec rolling shutter) the images would not align across the entire frame (Photoshop auto-align) because the camera had moved slightly during the 1/16 rolling shutter time causing different sub-pixel shifts across each individual frame. Shots taken with EFCS instead (about 1/250 shutter sweep time) did not have this issue to any noticeable degree. These shots were at 50mm and so the effect would be more or less for longer or shorter focal lengths. Even with IBIS on I suspect this would still be a problem for longer focal lengths because 1/16 is quite slow and of course even a 1/2 pixel misalignment will corrupt any attempts at super-resolution. I'd expect iWE's ability to align different regions of the frame separately would help to counteract this problem but probably best to just avoid it in the first place and avoid fully electronic shutter when using the technique on most cameras.

Hi Ken,

Thanks for that reminder! I am using the electronic shutter more and more, knowing that the rolling shutter won't cause any harm to speak of for most of the shooting I do. But you're right of course that it might cause alignment problems when stacking. It's obvious when you think about it, but I hadn't until now so an important reminder!

Lastly, I like the spectral sharpening approach! I experimented with that probably almost 15 years ago now in Photoshop by using the Gaussian Blur and High Pass filter functions to create layers that were each filtered for a different spatial frequency band. Happily those two filters combined do form perfect reconstruction filters so you end up with a set of layers akin to an equalizer. It worked quite well and a nice thing you could do was select particular bands to emphasize for creative benefit. For instance in the following photo I emphasized the spatial frequency band associated with the scintillation to emphasize it:

Interesting example! Like a coloristic watercolor painting!

Doing it in Photoshop with layers was of course a pain and just a proof-of-concept so I never went any further with it.

One question - do you do all your alignment and interpolation on the RAW data prior to demosaicing or is it all post demosaic?

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