Help Using GeneralisedHyperbolicStretch

Hi Zak

For your second a subsequent stretches it can be very helpful to switch to a log view of he histogram (the second button on the left above the graph).  The histogram "hump" (which you have peaking at around 0.2) represents primarily background, the brighter detail in the nebula exists more to the right hand side of the histogram graph but here the histogram values are "squashed" so you cannot really see the profile.  The log view is specifically designed to reveal this detail.  

If you switch to a log view on this image I expect the slope to the right of the histogram peak will be downward but quite "bumpy".  Bumps will reflect areas where pixel values have become "bunched".  This will correspond to a lack of contrast in your image.  Your image will likely improve if you set your Symmetry Point at these bumps - set a mid sized Local Intensity and then bring in a bit of Stretch Factor.  You should see the histogram graph gradually becoming more linear, less bumpy, and also see some contrast coming into the corresponding parts of the image.  You may need to do this in a few different places to get a pleasing result.

If things are getting too bright use the Highlight Protection slider to bring overall brightness down a bit.  Alternatively you can use the Shadow Protection slider to stop the background getting too dark.

It is difficult to be too specific because, of course, every image is different and your vision for your image will be personal but hopefully this gives a few more pointers to work with.

Let us know how you get on and any further questions that you have.

CS, Mike

Hi Zak,

can you point out which Adam block video are you referring to? I can t find it on yt, is it paywalled on his website? (i have his subscription anyway so i would be able to watch it)
Asking because i have the exact same problem as you, while i seem to be able to extract more faint detail and in general better SNR with GHS, what i dont like that i lose a lot of contrast in brightest areas especially against dark structures

Zak Jones:

Mike Cranfield:
Hi Zak

For your second a subsequent stretches it can be very helpful to switch to a log view of he histogram (the second button on the left above the graph).  The histogram "hump" (which you have peaking at around 0.2) represents primarily background, the brighter detail in the nebula exists more to the right hand side of the histogram graph but here the histogram values are "squashed" so you cannot really see the profile.  The log view is specifically designed to reveal this detail.  

If you switch to a log view on this image I expect the slope to the right of the histogram peak will be downward but quite "bumpy".  Bumps will reflect areas where pixel values have become "bunched".  This will correspond to a lack of contrast in your image.  Your image will likely improve if you set your Symmetry Point at these bumps - set a mid sized Local Intensity and then bring in a bit of Stretch Factor.  You should see the histogram graph gradually becoming more linear, less bumpy, and also see some contrast coming into the corresponding parts of the image.  You may need to do this in a few different places to get a pleasing result.

If things are getting too bright use the Highlight Protection slider to bring overall brightness down a bit.  Alternatively you can use the Shadow Protection slider to stop the background getting too dark.

It is difficult to be too specific because, of course, every image is different and your vision for your image will be personal but hopefully this gives a few more pointers to work with.

Let us know how you get on and any further questions that you have.

CS, Mike

Hi Mike,

Firstly, apologies for the extended period of time in between responses, I have had a lot going on in my personal life that made me unfortunately miss out on three months of astrophotography (plus the weather didn't help either).

Thanks for your pointers in using GHS. I have finally figured out how to use GHS properly, mainly thanks to your tips and Adam Block's videos on GHS.

It's a fantastic tool to use, and I have been getting much better results than I used to, especially in bringing out background elements in my images such as nebulae or dust whilst also retaining good details in the stars.

If I find any other issues when using GHS, I will be sure to reach out again, and I will make sure that I actually respond in a timely manner this time!

Zak

Hi Zak. I am glad you are managing to get GHS to work for you now. Adam's Stretch Academy series is very helpful - a real nuts and bolts look at the whole stretching landscape!  CS, Mike

Mike Cranfield:

Zak Jones:

Mike Cranfield:
Hi Zak

For your second a subsequent stretches it can be very helpful to switch to a log view of he histogram (the second button on the left above the graph).  The histogram "hump" (which you have peaking at around 0.2) represents primarily background, the brighter detail in the nebula exists more to the right hand side of the histogram graph but here the histogram values are "squashed" so you cannot really see the profile.  The log view is specifically designed to reveal this detail.  

If you switch to a log view on this image I expect the slope to the right of the histogram peak will be downward but quite "bumpy".  Bumps will reflect areas where pixel values have become "bunched".  This will correspond to a lack of contrast in your image.  Your image will likely improve if you set your Symmetry Point at these bumps - set a mid sized Local Intensity and then bring in a bit of Stretch Factor.  You should see the histogram graph gradually becoming more linear, less bumpy, and also see some contrast coming into the corresponding parts of the image.  You may need to do this in a few different places to get a pleasing result.

If things are getting too bright use the Highlight Protection slider to bring overall brightness down a bit.  Alternatively you can use the Shadow Protection slider to stop the background getting too dark.

It is difficult to be too specific because, of course, every image is different and your vision for your image will be personal but hopefully this gives a few more pointers to work with.

Let us know how you get on and any further questions that you have.

CS, Mike

Hi Mike,

Firstly, apologies for the extended period of time in between responses, I have had a lot going on in my personal life that made me unfortunately miss out on three months of astrophotography (plus the weather didn't help either).

Thanks for your pointers in using GHS. I have finally figured out how to use GHS properly, mainly thanks to your tips and Adam Block's videos on GHS.

It's a fantastic tool to use, and I have been getting much better results than I used to, especially in bringing out background elements in my images such as nebulae or dust whilst also retaining good details in the stars.

If I find any other issues when using GHS, I will be sure to reach out again, and I will make sure that I actually respond in a timely manner this time!

Zak

Hi Zak. I am glad you are managing to get GHS to work for you now. Adam's Stretch Academy series is very helpful - a real nuts and bolts look at the whole stretching landscape!  CS, Mike

I totally agree with you about Adam's Stretch Academy videos, they are unique and have a lot of information in them!

Looking forward to seeing what else you and Dave have planned for GHS in the future!

Zak