Astrophotography stacking: One shot colour workflow (Affinity Photo)

let's have a look at affinity photos astrophotography stacking feature and how we can use it to stack deep sky data from a one-shot color setup we will be using bayer sensor fit files and we'll be doing the entire workflow in a 32-bit unbounded linear color space no conversion to 16-bit is required to make use of affinity photos adjustments filters and tools which saves time and allows us to stay more non-destructive in our editing to start stacking let's go to file new astrophotography stack and we are taken into the dedicated persona or workspace for stacking on the right hand studio here we have our files panel and this is where we will add our light frames and calibration frames we can change the type of frame using the drop down here let's get straight into it and add our light frames so i will click add files here go to where my light frames are stored i'm starting with the 240 second exposure duration light frames so i will just select all of those and click open once added the frames appear in this list and you can click through to preview individual frames you can also reject frames from the stack by disabling the eye icon here so i might reject this frame because it has quite a prominent light trail going straight across the main deep sky object let's quickly add our calibration files so i will add the bios frames the dark frames again using dark frames that correspond with the exposure time of the light frames and then the flat frames we don't have any dark flat frames for this particular setup so we'll just ignore the dark flat frames type here okay let's just move back to the light frames and before we begin stacking let's look at some of the additional options we have here when stacking monochrome data especially from cameras prone to column errors and excessive hot pixels it is best to leave stacking method on sigma clipping however for bayer sensor data from one shot colour cameras and photographic cameras like dslrs and mirrorless bodies you can experiment with mean and median from experimentation these can sometimes yield slightly better noise levels in the stacked image however even though this is a one shot color camera setup quite a few of my frames have light trails going through them so i'm going to stick with sigma clipping because it will tend to reject those light trails as outlier pixels across on raw options you generally will not need to change the fitspayer pattern as it should be inferred from the metadata however if the result on your document view has a distinct bayer grid look and the colors are wrong you may need to manually specify the correct pattern for this camera the pattern is rggb but if i switch back to inferred you'll see that this was correctly identified anyway the mosaic method toggles between affinity photos bespoke demosaicing implementation and a simple bilinear algorithm in most scenarios the default method should be superior as it is sharper and yields fewer false color artifacts but if you need to use bilinear interpolation you can do so i'm going to switch back to the default method white balance allows you to choose from a d65 daylight white point the white point mandated in the camera metadata or to infer the white balance from the master flat calibration frame if you are using an astrophotography one shot camera or a modified photographic camera like a full spectrum camera for example letting the white balance be inferred from the master flat is actually quite useful since it should balance out any extreme shifts in color and i'm going to choose this option for our stack here okay with our settings configured let's click stack to begin the alignment and stacking process once stacking is complete we will see our final image clicking apply will now take us to the photo persona where across on the layers panel we can see we have a levels adjustment which is performing a gamma transform and then a curves adjustment for tone stretching we have our pixel layer here which is the stacked image data i'm just going to click into this and rename this to 240 seconds just to stay organized because with this particular subject the orion nebula it is infamous for having a core that is easily overexposed these light frames were 240 seconds in length and as a result most of the brighter detail has been overexposed now to counteract this i also shot a series of light frames at 10 seconds in length and we will stack these now and composite the two stacked images together so we will go through the same process add our light frames time using the 10 second frames the bias frames the dark frames again making sure to use dark frames that match the exposure time of the light frames so 10 seconds then finally the flat frames and of course not forgetting on raw options to set our white balance to be in third from the master flat then click stack now once this is stacked and we click apply it will be produced in a separate document so to composite this data into the other data here we don't need that curves adjustment so let's delete that and the levels adjustment we will clip into the pixel layer so click drag the levels adjustment offer it to the text just to the right here then release the mouse button and i will rename the pixel layer to 10 seconds again just to stay organized now we can copy this into the other document so command c on mac control c on windows go over to the other document and we want to paste our 10 second exposure stack above the levels adjustment here but below the curves adjustment so command v on mac control v on windows now our next issue is alignment if i just hide the 10 second stack you'll see there was a meridian flip here so this brings me to another useful compositing technique which is isolation mode let me just show this layer again now if we just want to see one particular layer we can option click it on mac or alt click on windows and that enters isolation mode so with this pixel layer isolated i can use v to select the move tool grab the rotation handle here and then hold shift to constrain to 15 degree increments and just rotate that 180 degrees now to exit isolation mode just click onto any other layer and we now need to align our two stack layers so affinity photo does have a star alignment feature under the arrange menu here but unfortunately the star features between the two stacks are not similar enough the overexposed stars are too bloated to be matched successfully to the thinner stars from the shorter exposure time i'll just come out of isolation mode select the 10 second layer set the opacity to 10 using one on the keyboard as a shortcut and now if i just click drag you'll see that i can roughly match these two layers up so let's zoom in and we can see here we can just match those stars up then to set the opacity back to 100 just use 0 on the keyboard and finally i can set the blend mode of the 10 second layer to luminosity okay now we've got our two layers blended together it's time to crop into the image so we can select the crop tool using c on the keyboard and then i'll just drag the crop handles in like so until i roughly get the composition that i want but don't forget that cropping is non-destructive so you don't have to permanently commit to any particular crop right now i'm happy with this so i'll use return on the keyboard to apply it for now and now let's do some tone and color work so i will move to the top of the layer stack add a new curves adjustment so command m on mac control m on windows and i'll use the picker functionality on the curves dialog so i can click on picker then what this enables me to do is just click drag to sample a particular area on the document then i can drag up like so just to push those tones up now we are at risk of overexposing the highlights here so i will just click drag to give that a little bit of a slope there so that we don't overexpose that core too early in our tonal work process okay the next thing we might want to do is remove the background color cast so we have a specific filter for that we can use i'll go to layer and merge visible this will just create a merged pixel layer of all of our work so far let's call this background removal then i can go to filters astrophotography remove background okay on my document view here i now have a sampler and i can drag this to a particular point in the background tones here then check sample color at handle if we don't like the way that the background has been subtracted to pure black we can raise the output black level until we're happy with how it looks and it's worth noting that you can actually tackle gradients as well with this filter if you click somewhere on the document view you can add additional samplers so you could add a sampler down here for example if you had a gradient going across your image but we don't need these additional samplers for this particular image so we'll just delete them and stick with one sampler we'll click apply to remove our background okay let's work on the colors now my preferred adjustment for color work is the selective color adjustment mainly because it allows you to push color groups around separately for example if we just zoom in here to see this in more detail on the reds here i'll increase the yellow contribution to 100 then reduce cyan slightly and immediately you can see that's really bringing out some strong vibrant color in that nebular detail if i move across to blues i can bring cyan up to 100 and yellow down to minus 100 and that just helps give some of the dust areas a more distinct color and identity in the image now speaking of dust areas if we move across two magentas we can reduce the magenta contribution to neutralize the color on these dust areas but also make them more prominent so again let's just see what happens when we move the magenta slider so going to minus 100 will remove that magenta color but actually make the detail stand out more okay the next thing we might do is add a brightness and contrast adjustment bring the brightness up and also the contrast but of course now we are overexposing the core detail so to quickly counteract this i will select the paint brush tool go across to the color panel make sure my active color is set to black increase the brush width and also just take down the hardness all the way to zero percent for a nice soft edged brush and just single click into that core there so we've subtracted this area from the brightness and contrast adjustment mask meaning it can affect the rest of the image but avoid over exposing that core one final step then we might want to bring out some more structure especially in the nebular detail so we can do this non-destructively using a live clarity filter but by default live filters child layer into the layer that we just had selected on the layers panel so we can just click drag this out at the top of the layer stack like so then increase the strength until we really start to bring out some of that detail however this effect is a bit strong if it's rendering on the whole image so what we will do is go to layer invert and that will invert the clarity mask so once again we can get the paintbrush tool this time set our color to white and then just paint into the areas where we want that clarity filter to render so now if i show you the before and the after you'll see that is quite a dramatic difference and because this is a live filter if we feel that perhaps the effect is too strong we can just double click that clarity filter and bring the strength down slightly and there we go i will leave the edit there for now but i would encourage you to experiment further do watch the other astrophotography video tutorials as i use various techniques and features in each one depending on the image being edited i hope you found this video useful and thank you for watching

Channel: Affinity Photo

Views: 26,455

Keywords: Astrophotography, stacking, oiii, ha, calibration, nebula, Affinity Photo, Photoshop, 32-bit, linear, tone stretching

Id: fOMF8CScG_A

Length: 16min 5sec (965 seconds)

Published: Thu Feb 04 2021