Drizzle causing problems

[alan potts]

A great question to ask anyone from home. Drizzle, I tried it in DSS just because it is there even though I am not totally sure what it does.

Now I only have 8gigs of RAM on the machine here in the basement which I tend to use for everything, The drizzled file is 925mb which is a a bit bigger but not massive however its more than the normal 180mb area.

My computer using PS CC tells me not enough RAM to open it, any ideas why, as I thought it would not be too big at this size, seems a bit strange to me.

Alan

[alan potts]

On 29/10/2019 at 16:15, KevS said:

Alan, I am experiencing some similar problems; I have a similar capacity machine (RAM). Endeavoured to process some DSLR (Canon) subs this morning, getting massive files when processing in PS(7) and Gimp(2.10.12). DSS took about 6 hours to register, stack and align 231 x 180s subs. The laptop I use has recently updated itself to the latest incarnation of windows 10. I have also noticed that manipulating the image within either image processing programmes the files get progressively larger until the RAM is no longer able to cope. 

Hope someone out there has some ideas.

K

Been in hospital and have just seen, I am raising this with my friend later, he is an IT guru and if sorted I will let you know.

Alan

[vlaiv]

Just don't use drizzle - no point in doing so.

Drizzle as algorithm works only when you have certain preconditions, and in practice no one having amateur setup will have these preconditions met. There simply is no benefit for doing drizzle and it only "hurts" your data.

In order to utilize drizzle algorithm, one needs predictable PSF, oversampling based on that PSF and means to point their scope with sub pixel precision. It requires guide system and imaging system to be connected in such way that dither issued by guide subsystem result in exact pixel fraction shift of imaging system. While this in principle can be done - no software support exists (that I'm aware of).

[alan potts]

15 hours ago, vlaiv said:

Just don't use drizzle - no point in doing so.

Drizzle as algorithm works only when you have certain preconditions, and in practice no one having amateur setup will have these preconditions met. There simply is no benefit for doing drizzle and it only "hurts" your data.

In order to utilize drizzle algorithm, one needs predictable PSF, oversampling based on that PSF and means to point their scope with sub pixel precision. It requires guide system and imaging system to be connected in such way that dither issued by guide subsystem result in exact pixel fraction shift of imaging system. While this in principle can be done - no software support exists (that I'm aware of).

That sounds like a good reason to forget it, I was only trying it because it was there in DSS, thanks

Alan

[sharkmelley]

Drizzle works best on undersampled images.  Standard (random offset) dithering is all that is required.  I use Bayer Drizzle (sometimes called CFA Drizzle) as part of my standard processing workflow and it's especially beneficial for OSC cameras or DSLRs because it increases resolution by avoiding the interpolation that takes place during debayering.  The other advantage it gives is a more finely grained noise structure than standard stacking, which helps with noise reduction. 

It's definitely well worth a try!

Mark

Edited November 10, 2019 by sharkmelley

[vlaiv]

1 hour ago, sharkmelley said:

Drizzle works best on undersampled images.  Standard (random offset) dithering is all that is required.  I use Bayer Drizzle (sometimes called CFA Drizzle) as part of my standard processing workflow and it's especially beneficial for OSC cameras or DSLRs because it increases resolution by avoiding the interpolation that takes place during debayering.  The other advantage it gives is a more finely grained noise structure than standard stacking, which helps with noise reduction. 

It's definitely well worth a try!

Mark

How about an experiment?

I'll provide you with undersampled images with random offsets - and you perform combination of those images:

1) Drizzle method

2) Resampled integration

We examine results for SNR and sharpness (PSF FWHM) to see if it actually works the way people expect it to work?

Btw, by Resampled integration I mean - You take each undersampled sub and prior to stacking you resample to adequate size using Lanczos-3 resampling for example (adequate in this context means equivalent of drizzle factor - if you drizzle x2, you resample to x2 larger size). Then align/register these resampled images using Lanczos-3 and stack with average stacking method.

[alan potts]

Sounds interesting, the one thing I didn't get an answer to is why a file which is in fact only 541mb will not open in PS, on a 8gig ram machine. 541mb is nothing and it is telling me not enough RAM.

Alan

[PhotoGav]

How much of the 8GB RAM is made available to Photoshop? There is an option in PS Preferences to assign RAM to the application. Have a quick check in there. Might be a total red herring, but worth a look...

[alan potts]

On 10/11/2019 at 15:53, PhotoGav said:

How much of the 8GB RAM is made available to Photoshop? There is an option in PS Preferences to assign RAM to the application. Have a quick check in there. Might be a total red herring, but worth a look...

Thanks Gav, my IT mate found this and sorted the situation though with being in Hospital I had forgotten about the thread after Vlaiv had basically told me it was a waste of time using it, his knowledge much greater than mine.

Many thanks in any case.

alan