PixInsight Forum (historical)

PixInsight => General => Topic started by: akoenig on 2018 July 15 08:57:01

Title: File size inflation
Post by: akoenig on 2018 July 15 08:57:01

Hi,
I could not find anything on this Topic so far, so Maybe someone could explain to me, why PixInsight inflates processed files so much?


The initial file size is approx. 25MB per exposure (ASI294MC Pro). Once I've completed the processing, the final size is almost 500MB! (FITS and XISF files). Does this happen to everyone?

I can understand that a Project can easily exceed several hunderd MB, because all of the open files and the processing history etc. But a single processed Picture does not contain all this Information, so why is this Happening and is there any way I can Change this behaviour?


Thank you and Regards,
Allen

Title: Re: File size inflation
Post by: Geoff on 2018 July 15 13:48:39

It shouldn’t happen. You will need to detail your processing steps for someone to diagnose the problem.

Title: Re: File size inflation
Post by: pfile on 2018 July 15 14:28:56

its completely normal.

the original files are almost certainly 16-bits per pixel mono CFA files. thats 2 bytes per pixel. then 2 things happen -

1) the image is calibrated. because it would be foolish to stay in 16-bit integer format after dividing the master flat, the images are now 32-bit floating point. that doubles the size.
2) the images are debayered. they go from 1 channel 32-bit images to 3-channel 32b images. that triples the size from step 2.

so, there is a factor of 6 growth.

any astro processing program is going to do this, because its the only right thing to do. with large sensors (APS-C and larger) with tiny pixels it very quickly gets out of hand.

rob

Title: Re: File size inflation
Post by: akoenig on 2018 July 16 12:29:13

Thank you for the Information.

Regards,
Allen