June 24 2026 APP 2.0.0-beta46 has been released !
Improved internal memory configuration (lower ! memory usage), fixed beta45 startup issue, fixed Set Save Directory & 2-panel mosaics.
May 27 2026 APP 2.0.0-beta45 has been released !
Fully Multi-Threaded LNC, many improvements for the registration engine, platform upgrade, and further tuning of internal memory consumption and memory release back to OS.
Apr 14 2026: Google Pay, Apple Pay & WeChat Pay added as payment options
Update on the 2.0.0 release & the full manual
We are getting close to the 2.0.0 stable release and the full manual. The manual will soon become available on the website and also in PDF format. Both versions will be identical and once released, will start to follow the APP release cycle and thus will stay up-to-date to the latest APP version.
Once 2.0.0 is released, the price for APP will increase. Owner's license holders will not need to pay an upgrade fee to use 2.0.0, neither do Renter's license holders.
Good day to all! I have been a happy APP user for several years now and am actually beginning to feel at home with the application. Rather than just use and tweak the DDP stretching presets and just being happy they work so well (e.g. 15% BG, 5 sigma, 2.5% base), I find myself now asking, "What exactly am I selecting for this image?" I have done a fair bit of searching on this site and on the web but am coming up empty. About all that I can find is in the "Preview Filter Instructions," which is not much. Without giving up the corporate crown jewels would you be able to elucidate, or provide a reference? Thanks!
Regards, Martin
I'm not sure I completely understand the question, do you mean to ask what a best kind of setting would be for a certain image? Or what exactly the values mean
@vincent-mod - I would like to know what the values represent. I would like to better understand what is being affected when the individual values are changed.
Ok, thanks for clarifying! I'll pass this on to Mabula as he likely has a more detailed response on this.
Hi @martinontheroad,
Thank you very much for your question.
15% BG, 5 sigma, 2.5% base :
means that the image will be stretched so the peak of the histogram is at 15% of the data range. So for a 16bit image, the data range is 0-65535, then 15% means 0,15 * 65535 = 9830 . For 32bits float data, the range is from 0-1, so then the peak of the histogram will be at 0,15 * 1 = 0,15 .
The sigma determines the width of the peak after the stretch. with 5sigma, from the peak in the histogram to the black point of 0 will be 5 sigma, with 3 sigma, it will be 3 sigma, this means that with 3 sigma you will stretch the data stronger when compared to 5 sigma. So with 3 sigma you will see more noise than with 5 sigma.
2,5% base means that a 2,5% aritifical pedestal is added to the data. So for 32bits float data in range of 0 - 1. It means that the range of 0 - 0,025 will have no data. The remaining data range of 0,025 - 1 will then be used to stretch the data in that range. It has the upside that you get better contrast in low lights of the image, so faint fuzzies will be better visible. The downside is that you lose some contrast in the result when compared to using no base (or base 0%).
Please let me know if this answers your question.
Mabula
Mabula
Many thanks for taking the time to reply to my question. I have a much better understanding now of what is going on “under the hood.”
A lingering question regarding “sigma.” When it comes to a Gaussian-like distribution of data, I am used to thinking of sigma as a standard deviation, with 5 sigma being further away from the center than 3 sigma. I visualize a 5 sigma curve as being wider than a sigma one. In APP, it is the opposite, so my understanding must be faulty.
What does sigma represent in APP? Is it related to a sigma clipping algorithm for noise/outlier rejection? Thank you for considering my questions.
Kind Regards, Martin
Dear Martin.
Sigma is the dispersion/scale of the distribution.
For a normal/Gauss distribution this equals the standard deviation.
So for any gauss or gauss like distribution, the 3 or 5 sigma in APP's preview filter indicates the distance from the peak to the black point of 0. So with 3 sigma less of the distribution is showed on the left side of the histogram, with 5 sigma more is showed meaning that with the peak at the same location, the data will be less stretched 😉
Hope that explains it better?
Mabula
Mabula - Thank you for such a concise response. It makes perfect sense. Now to figure out how to use this information to improve my APP images! Have a great week.
Regards, Martin
