Generalised Hyperbolic Stretch - Beginner Tutorial

hey guys how's it going I've been receiving a lot of messages just recently asking me if I'd make a video covering the new tool generalized hyperbolic stretch and aside from being one of the most snappily named tools on the market it really is a performer let's get straight into it guys so first of all from an opened Pixi site window I want you to click resources click updates and then manage repositories from here click add and point this little URL box to the one that's located in the video description box just down below should be this one right here ghsastro.co.uk forward slash updates hit OK on that until everything's closed back down and ready to go then hit resources once again click updates once again and this time press check for updates now the next time you close and reopen pics Insight the tool should be installed and ready to go and you will find them if everything went well inside processors and intense Transformations right there generalized hyperbolic stretch so let's go ahead get that thing opened up and ready to go now it's it's a pretty threatening window I have to admit the first time I opened this thing I thought ah where do I start but um a little bit of messing later and I think it's a very good tool and I can certainly see it becoming a part of my workflows going forwards and I hope so for you too because it gives you more control than ever really over accurately targeting your stretching efforts in your images So to that end I've prepared three separate images I want to work on as quickly as possible basically through this tutorial and uh it's these three sets here so first of all we've got one shot color dual narrowband data to work on we've got monochrome H Alpha data to work on and finally some RGB One Shot Caller Broadband Galaxy data to work on and let's just get going on them one at a time so first of all I'm gonna click the window I actually want to work on this is the the Broadband sorry dual narrowband one shot color data and I'm gonna open a preview window from within generalized hyperbolic stretch once that's done uh the first task that I've been performing on this thing is to actually set the black point on the image so to do that I'm going to click the little icon there that says log that's a logarithmic histogram View I'm gonna change the transformation type to a linear transformation and then by selecting an area just behind the left hand Edge of the the actual distribution of the histogram right there so around about here is fine not into the data certainly not deep into the data and not miles away from the day I would anywhere around about here if you can just see on my screen if I make that a little bit bigger hopefully this becomes uh more apparent what I'm talking about anywhere around about here is a good black point to set on your image and once that's done click Send to BP hit apply reset the tool good to go on the next step it should have changed everything back to transformation type being generalized hyperbolic and close down your logarithmic view just click very generally anywhere on the on the image if you like are actually on the uh the graph window right there using the zoom tools you can zoom in just a little bit uh start to get this thing viewable so as I've done here you can see now the pixel values tend to be represented on this histogram so we've got the red pixels the green pixels the blue pixels and the intersections of those where you know where the blue meets the green and we get these teals uh where the red means the yellow and we red meets the green rather and we get these yellows but also you'll see this big gray Mass right here that's the the body of the Venn diagram if you will the central point where everything converges um so I'm going to select for this first stretch smack in the middle of that gray area right there so this looks pretty good it doesn't have to be perfectly precise you know what I mean just anyway near the middle we're not too weird about the verticality of this thing just the horizontal middle um so we're on generalized hyperbolic stretch I'm going to click send that to the Symmetry point so it's going to take the value that we've just selected and apply it into this box right here s p can also adjust the slider if you wish to fine tune this later well now I'm going to start to apply the stretch factor you can if you wish reset the histogram view right there get a better overview of what's going on that up that stretch factor until the day is becoming visible bear in mind this is an iterative process don't kind of overcook it and try and do everything in one because you will inevitably do more harm and good unfortunately so uh just a little bit of a stretch a step in the right direction each time and now if I alter the local intensity if you just pay attention for a moment to this red line while I start to move this local intensity slider to the right you can hopefully see the fur right I go the more vertical effectively the um the central point of that red line starts to get so it's going to be putting its efforts in transforming the broadest part of that data right now now the best way I think to to make these adjustments is by literally just sitting there and looking at the preview window while worrying less about exactly what numbers you're landing on with your mouse hand and this then just make it look like a reasonable step in the right direction so that's to say not too far not so small that you're gonna have to make a million iterations but you know around about here nothing's overcooked it looks alright I'm gonna go ahead apply that reset the window once more and now you can start to get a little bit more selective with this stretch if you would wish so you can have a select using the actual graph view right there the parts of the image you'd like to work on or using your left Mouse button on the preview selecting different regions hopefully you can see that yellow line moving around it's gonna work on different parts obviously if you want to work on background regions select a background region it'll put Yara your symmetry point in the right area fire if you want to work on mid-tones it's like the mid-tones that kind of thing so I think I'm going to use probably around this this Edge right here as a good value I think to work on again we can mess with this a lot so don't worry too much about getting this perfect just start making baby steps in the right direction and it'll all start to make sense so once I've selected that I'm going to send that once again to the Symmetry point that new value that we've selected you'll start to alter the stretch factor this time be a little bit more gentle on that stretch because it's very easy to as you can see massively uh massively overcook this one so just a little bit of a step in the right direction an alteration there on the local intensity a little boost [Music] think that's looking reasonable now I'm just gonna make sure that I've got the right symmetry point for me selected just by basically dragging it around a little bit moving it left nah doesn't look as good move it too far right look is good you know what I mean it's not an exact science you really are best off just focusing on that preview window that's the thing that really matters how does your image look rather than you know what the numbers say on the right hand side so I'm gonna say there looks pretty good to me looks about right or head apply that and that looks like a pretty well stretched image I'd probably like to dial in the Black Point just a little bit more so once again if you wish you can open up linear stretching mode and select an area just off the left hand side of that main histogram distribution so see being careful to not select into any regions where you'll start to clip pixels which making sure you're just behind where you need to be send that to the like Point as you can see it looks pretty good again don't be shy about sliding around the the black point right here just keeping an eye on it you know what I mean you could probably set it yourself like this so you can see that's way too bright that's way too dark it's it's not really uh it's not rocket science so around about there looks a little bit overcooked that looks good to me so I'm going to settle at that and I'd call that pretty well stretched image it looks good to me now I'd be happy to move on with further steps of processing at that point so I'm going to call that one Dawn that's one demonstration take a look now at this mono ha data so I'll reset the tool click the window I want to work on open a preview once again I'm going to click that logarithmic view once again and first of all using the linear transformation type select myself a Black Point hopefully you can see if I just make this window a bit bigger exactly what I'm doing so send that to the black point it's not too far to the right it's not too far to the left just set nicely not clipping any data is the most important part so go ahead and close the logarithmic view if you like select again a broad part of the data or just anywhere on the image that's fine we should be back to generalize hyperbolic mode to send this to the the Symmetry point and zoom up just a little bit make sure that's accurately placed and we can see it isn't I'm actually off to the front I'd rather be selecting around the middle so you can see we're roughly equidistant from left to right through the broad part of this histogram uh view right here I'm going to send that instead to the Symmetry Point start to stretch reset the window if you want to keep an eye on things again I don't think it's that important but just get the data visible start to alter the local intensity sliding it over to the right being careful to not you know not go too fast make baby steps with this thing it's it's not too bad so that looks good to me which happens to just be a value of about 10.32 on local intensity your mileage will vary it'll be of a different image to image reset the view let's make another small transformation so I'm going to go for the broad part of the data I think once again send that to the Symmetry point once again boost the stretch factor a little bit boost the local intensity a little bit be careful to not do this to your image where it's going to look absolutely horrendous and that's looking reasonable maybe a little bit stronger than I'm looking for so that looks good and now I reckon the final black point adjustment on this thing and about there just take a look at that slightly darker than I'm looking for so drag that black point to the left that looks good to me all right I'm happy with that as you can see that's just taken me even while demonstrating it and trying to talk through it moments and I've got a nice stretch applied to this image okay so it's a pretty powerful tool now one final goal this time on broadband RGB data it's the invisible voice so select the image you want to work on open a preview and then using linear mode with a logarithmic view I'm going to set the black point so I'll open it once again you see the main Spike of the histogram the main body of it right there just off to the left a little bit of breathing room not over here not in here that looks good to me set that to the Black Point apply reset the whole tool okay next up like I say let's select either an area of the image with a left Mouse button or place it in the body of it logarithmic view can be turned off now by the way um once again can't really see what we're doing so you could either click the zoom button and look at it that way or I'd rather just click it up a little bit or even type in a number manually that suits the the width of your particular histogram distribution gonna go for the broad Point like this it's a little bit too big to see on the screen whoops that looks pretty good that's roughly through the broadest point of all the data the gray point on this as you can see is much more centralized on broadband um calibrated data but all the same send that to the Symmetry point start to bring up the stretch factor just a little bit I'll leave that deselected so you can keep an eye on what's going on and more importantly just keep looking at the uh the preview window there that's the really important thing in it how the image actually looks like I say so uh stretch factor sliding across the right a little bit don't go crazy don't make two small moves Goldilocks zone that's what we're looking for a little bit of an alteration there in the stretch factor is boosted up it's looking pretty good it seems like we've landed on again 6.4 so it's not like any of the other images really so apply that reset the tool select an area of the image I actually want to work on once again so I'm gonna this time draw a title preview so I can be more accurate with my selection and I'd say perhaps I want to work on the fainter regions of these spiral arms in the Galaxy so maybe I'll select one manually like down here or down here here you get the idea select the parts of the image you really want to work on yourself let's just put it on the foot of this distribution right there you could again if you wish go smack through the middle and see how that looks experiment that's the beauty of it no two data sets are going to be exactly the same so I would never try and deal in hard and fast rules for this thing uh just experiment give it a go so send that now whatever you select the asymmetry point start playing a stretch you see the effect that we're having and again how easy it would be to go way too far with this thing but a little bit of a stretch a little bit of a boost in the local intensity of this so you can see the effect once again it's having on that red line I just move this across the verticality of it is changing but just looking at the image itself around about there looks to be what I'm aiming for I would say if I just cycle the preview window back and forth you can hopefully see it's a step in the right direction we could go ahead with that and let's say that's a nicely stretched image once again if you want to again alter the Black Point just use the linear tool plonk it behind and um take a look do you know what I mean like that's the best thing just just learn by doing I would really say so again I've got it slightly wrong it's a little bit too aggressive so maybe just slide that to the left to touch you know what I mean no harm done go ahead and apply it at that and I think we've got three white nicely stretched images there in a matter of minutes all while doing a running commentary so hopefully you can see don't be afraid of the tool get it downloaded and have a play uh you've got nothing to lose so guys that's about it I hope that that introduces this tool to you in some small way and that you have a load of fun trying it out that's the thing this is really all about and it having some fun and and enjoying life so uh yeah with that said guys thank you all for your support it means the world to me and doing this whole thing would be just about impossible without you guys so thank you thank you all very much from the bottom my heart and I will see you in the next one so until then look after yourselves and those around you and uh fully please guys

Channel: lukomatico

Views: 18,657

Keywords: astronomy, astrophotography, telescope, best telescope, pixinsight, lukomatico

Id: WXY5kOFaxaI

Length: 16min 10sec (970 seconds)

Published: Fri Jul 07 2023