Sanseb Posted March 25, 2022 Share Posted March 25, 2022 Hey James, is there a way to create/add arcsin hyperbolic curves for Stretching Data in Affinity similar to Photoshop? It´s being said that stretching with this will preserve star size and color balance. I would like to give it a try? See this link for further information: https://www.cloudynights.com/topic/595610-photoshop-color-preserving-arcsinh-stretch/ Cheers, Sebastian Quote Link to comment Share on other sites More sharing options...
John Rostron Posted March 25, 2022 Share Posted March 25, 2022 The answere seems to be No. Although field expressions can use sine, cosine and their arcs, there is no hyperbolic equivalents. Neither is there an exponential or logarithmic fumction. You might like to add a comment to my request for exponential function. John Alfred 1 Quote Windows 10, Affinity Photo 1.10.5 Designer 1.10.5 and Publisher 1.10.5 (mainly Photo), now ex-Adobe CC CPU: AMD A6-3670. RAM: 16 GB DDR3 @ 666MHz, Graphics: 2047MB NVIDIA GeForce GT 630 Link to comment Share on other sites More sharing options...
Alfred Posted March 25, 2022 Share Posted March 25, 2022 41 minutes ago, John Rostron said: Although field expressions can use sine, cosine and their arcs, there is no hyperbolic equivalents. Neither is there an exponential or logarithmic fumction. If we at least had natural logs we could use the following formula: arcsinh x = ln[x + √(x² + 1)] John Rostron 1 Quote Alfred Affinity Designer/Photo/Publisher 2 for Windows • Windows 10 Home/Pro Affinity Designer/Photo/Publisher 2 for iPad • iPadOS 17.3.1 (iPad 7th gen) Link to comment Share on other sites More sharing options...
Lisbon Posted March 25, 2022 Share Posted March 25, 2022 Its been a while but i remember trying to replicate this in affinity photo. I wanted to see if this method could be useful for recovering shadows. I failed. If im not mistaken its not as simple as just applying arcsinh(x). The original info gives some clues: "The calculation of the curve was a very interesting problem. I eventually solved it by working backwards from the final Arcsinh curve in an iterative manner from the final point backwards - building a curve that with a double lookup matched the Arcsinh curve as closely as possible." John Rostron 1 Quote Link to comment Share on other sites More sharing options...
Lisbon Posted March 25, 2022 Share Posted March 25, 2022 There is a video in Czech (i think) on youtube about this topic. Unfortunately i dont understand a single word. TekBo Studio: Rozšíření dynamického rozsahu pomocí Arcsinh v Affinity Photo Quote Link to comment Share on other sites More sharing options...
v_kyr Posted March 25, 2022 Share Posted March 25, 2022 3 hours ago, Lisbon said: There is a video in Czech (i think) on youtube about this topic. Unfortunately i dont understand a single word. TekBo Studio: Rozšíření dynamického rozsahu pomocí Arcsinh v Affinity Photo Also the Youtube Video descr. references some "Arcsinh Transformation into Affinity Photo curves" values ... arcsinh-transform.pdf Lisbon 1 Quote ☛ Affinity Designer 1.10.8 ◆ Affinity Photo 1.10.8 ◆ Affinity Publisher 1.10.8 ◆ OSX El Capitan ☛ Affinity V2.3 apps ◆ MacOS Sonoma 14.2 ◆ iPad OS 17.2 Link to comment Share on other sites More sharing options...
Lisbon Posted March 25, 2022 Share Posted March 25, 2022 Thank you @v_kyr Quote Link to comment Share on other sites More sharing options...
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