How to FOCUS STACK at Night

today's video is sponsored by squarespace a platform where you can design beautiful websites and host your online store in landscape astrophotography we're forced to use wide open apertures like f 1.4 f 2 f 2.8 and the downside to that is that we have a very limited depth of field to work with so when you focus on the stars or focus to infinity the immediate foreground is out of focus and blurry now it would be nice to use f8 f11 or f16 like daytime landscape photographers and have everything sharp and in focus in a single exposure but then we wouldn't collect enough light and our images would be pretty much completely black so to overcome the limitation of the wide open apertures we can use a technique called focus stacking where you take multiple images focused at different points throughout the scene blend those into one image where everything is sharp from front to back but before i teach you how to focus back at night it's worth learning how you can avoid the need to focus stack in the first place and for that we need to learn about something called the hyperfocal distance the hyperfocal distance is the distance to focus at to get the maximum depth of field for the current focal length of your lens and the aperture setting that you're using that's a bit of remarkable so let me say it again but slightly differently if you focus at the hyperfocal distance which will change depending on the focal length of the lens you're using and the aperture setting that you're using everything from infinity to half of the hyperfocal distance away from you will be in acceptable focus now the beauty of knowing the hyperfocal distance is that if you focus to infinity so if you focus on the stars everything from infinity to the hyperfocal distance will be in acceptable focus so if you focus on infinity instead of the hyperfocal distance you lose that half distance of the hyperfocal distance of acceptable focus so you don't lose a lot i'd be careful about searching for hyperfocal tables on the internet because a lot of them are from the film days and they're more tuned for film cameras they're not quite up to date for high resolution digital cameras so i always use the app photo pills so you open up the pills and then go to the hyperfocal table let's say for example i'm using my 14 millimeter lens i've got my camera in there the sony a7 iii and i'm sure in a f 2.8 i can see that the hyperfocal distance is 2.34 meters so if i focus on the stars focus to infinity everything from the stars to 2.34 meters in front of my camera is going to be sharp and in acceptable focus so if i didn't want to focus stack maybe it's windy outside for example um then i would make sure my tripod is nice and high so it's away from the foreground and don't aim sort of completely down and that way you know everything is going to be sharp and in focus from front to back so ultra wide angle lenses and wide angle lenses do actually have a lot of depth of field even when you're focused to infinity but if you wanted to focus stack of course if you needed to focus stack you can focus stack at any focal length uh but my favorite technique with focus tracking is using an ultra wide angle lens and getting up close and personal with the foreground so there might be some a small bunch of flowers in the foreground which are nearly a tiny speck in the grand landscape but when you get up close and personal with ultra wide angle lens it really makes them big in the frame and makes them the main subject and sort of emphasizes them in your image so let me show you guys how it's a focus stack at night [Music] so i found a nice composition here got some rocks in the immediate foreground that will be out of focus in a single exposure but i'm not very close to the rock so i don't think it's going to take me many images to get all the images i need to focus stack sometimes i can be right down on the ground about 10 to 15 centimeters away from my main subject but in this instance i'm not too close to the foreground but it will still need a focus deck and now it's time to start collecting all the exposures i need so when it comes to focus stacking at night the first exposure i'll take will be focused on the stars focused at infinity once you've taken that image review it on the back of your camera zoom in and find the point where the focus is dropping off if it's exceptionally dark and you can't see much detail in the foreground of your image try taking another exposure with a higher iso than you would normally use so you can kind of see where the focus is dropping off or the second technique is of course to use live view on the rear lcd of your camera and shine your head torch into the scene zoom in using live view and from there you should be able to see where the focus is dropping off and then you can focus on that point so focus stacking at night requires you to turn a head touch on into the scene so that you can focus on the next point and that's quite an intrusive method especially if there are other photographers in the area um it's going to annoy them and ruin their night so you know think of some basic etiquette and try not to ruin other people's nights but there are some things you can do to avoid the need to turn your head torch on so what you can do instead is to walk into the scene turn your phone on so that you can see the screen and then leave the phone uh sort of in the scene somewhere where the focus was dropping off and then you can focus on the phone light take the phone out of the scene before you capture your next exposure if you don't want to put your phone on the ground you can use something like this just a little led so it's a bit less intrusive than shining a bright head torch but but it's always worth thinking of others around you and uh trying not to spoil their fun another technique um i'm not sure if all cameras have this but on my sony bodies when i'm focusing there's a dial at the bottom which tells you roughly how far into the scene you're focusing and every time i'm focus stacking i pay attention to that dial and remember the numbers so i start at infinity and then maybe 10 meters seven meters five meters three meters one meter um i kind of remember how many shots i needed in that scenario and i could just use that scale on the bottom and that way i don't need to turn my head torch on and i don't ruin the night for other people a quick break in today's video to talk about the sponsors squarespace squarespace is the place to host your website or online store and i should know because i speak from personal experience my website's been hosted on squarespace for years now and i've been a very happy customer if you want to find more useful videos like this you can head on over to my blog page you can also check out the galleries on my website which look absolutely amazing thanks to the lack of compression of the images you can also check out my online store where you can buy my astro workflow lightroom presets for example squarespace handles all the payments everything is automated and it means i can spend more of my time doing things like making useful tutorial videos and taking beautiful images if you'd like to give squarespace a try head on over to squarespace.com forward slash allen use one of their award-winning templates to get you started and when you're happy to go live with your website use the code allen at the checkout for 10 off your first purchase of our website or domain with squarespace [Music] all right so now it's time to do the editing and i'm going to use some different images that i captured in the field in the video you just saw i've got these four images here of some thai nasty plants internal reef backlit by the moon this one's focused right on the foreground as i go across focus further and further away so we're focused on the stars and we're focused on infinity so before i take these images into photoshop i'm just going to do some basic edits so i'm going to lift some detail on the shadows so i can see what i'm working with when we're doing the focus stack maybe lift the blacks just a touch and recover some highlights by dropping the highlights down the white balance could be fixed so let's try auto that's way too warm for me so i'm just gonna manually adjust until i have something i'm looking for i don't want to blue somewhere around there looks good and just going to remove the tint next up i'm going to come down to the lens correction tab remove chromatic aberration enable the profile correction to get rid of the lens distortion and the vignetting that looks great and i'm actually going to leave noise reduction until after i've stacked the image that gives me more flexibility if i ever come back to re-edit this image i don't have to focus stack it all over again if i'm not happy with the noise reduction now all i need to do is select all of the images down here in the film strip make sure they're all selected and just click sync check all so that all of the edits are going to be synchronized between all four images and there we go they're all looking pretty much the same now apart from the focus and i'm just going to right mouse click edit in open as layers in photoshop right on the bottom here so don't click on the edit in photoshop make sure you click on the open as layers now once they've all been opened as layers in photoshop it's a good idea to find the sky image and bring it to the top of all the layers so you can do that by turning off the visibility of the uppermost layer until you find the one which is focused on the stars and focus to infinity what i'm going to do is i'm going to click and drag make sure that lays on top i'm going to rename it to sky so i know it's the sky exposure and then turn the visibility of all the layers back on you'll see why this is important shortly now as i turn the visibility of the layers on and off you'll notice that the field of view slightly changes between each of the images it's almost as if i zoomed in and out as i was changing the focus in this is actually something called focus breathing some lenses exhibit focus breathing more than other lenses some lenses don't have focus breathing but just to be safe and sure select all of the images in the layers panel by clicking one holding shift and clicking the bottom layer and then come up to edit auto align layers and just leave it set to auto don't need any vignette or geometric distortion correction just click ok and what that's going to do is it's going to line up all the images so that they're all perfectly aligned and on top of one another rather than zooming in and zooming out depending on the focus point so now when i turn the visibility of the layers off you'll notice that there's no zooming in and zooming out and they're all perfectly aligned with one another you'll notice there's a white border now because it had to shrink some of the images but we can crop that later on that's fine in fact we could do that now just to be safe so i'm going to crop that in make sure i've got no empty space on the uh the most shrunken image i think that's looking good so it took the visibility of all the layers back on i've got all of the layers selected i'm going to come up to edit auto blend layers leave it to stack images i don't like the seamless tones and colors just leave it as it is because all of the images had the same exposure settings and then you can leave content away field ticked if you want it usually never needs to do anything anyway and photoshop is just going to work its magic here and select the sharpest portion of each region of the image once that's done it spits out a new sky merged layer um i'm going to delete this because i want to work on these layer masks because as you can see photoshop's not done a very good job on the sky there's some autofocus stars there and this is why it's really important to have the sky image on top because now we can easily fix that so what photoshop has done is it's created a layer mask which is these things here for each of the frames and if i hold alt or option on a mac and click on the layer mask it shows me the layer mask basically anything that's white shows through anything that's black gets hidden so you can see this was the sky exposure so most of the sky is showing and some of the sort of distant foreground is showing um but it's not used any of the foreground here which is exactly what we want so um but the issue is as you can see there are some black splotches in the sky and that's why we're seeing out of focus stars from the layers underneath so what i'm going to do is make sure the layer mask is selected here just by clicking it once and you'll see white sort of borders around the corners i'm going to select the brush tool i'm going to make sure i've got white as the foreground color normal as the blending mode opacity is 100 i'm going to change the size of my brush by right mouse clicking and adjusting the size or you can use the square brackets on your keyboard and i'm going to paint in white over these autofocus stars and what i'm actually doing is painting on this layer mask so i'm painting white and saying show that part of the sky image so i'm going to paint over all of the sky here um if you want to see what you're doing live you can just click on the the layer here but then when you're painting just make sure you've clicked on the layer mask and it's active so i'm just going to keep painting here bring those sharp stars back and now i'm just going to take a closer look at the edges because it did a very rough job and this horizon is looking fine looking great everything sharpened in focus you can see some autofocus stars close to the edge of this tiny nasty plant so i'm gonna make my brush smaller and just paint over those bring those sharp stars back lovely another one there another one there and another one there now we're looking pretty good another one there just gonna continue to brush there quickly that's now looking great uh we just check the rest of the image just in case there's anything else we need to fix by changing the layer masks can't fix that lens flare using layer masks unfortunately um but it's looking good it stitched the image pretty well but if it hasn't stitched the image pretty well you can fix it in the layers here so i think here there's a little bit of an autofocus plant going on so let's just zoom into that yeah you can see it kind of just stops there so let's find out what layer that is so the sharp one is here and it's put a blurry bit on top so the first thing i need to do is take a black brush this time and just hide that blurry section of plant and then on the layer underneath i'm just going to use a white brush and bring that sharper version through there we go that looks better there we go we have our final focus stacked image now you can go about editing the image so for example see if we can get rid of this lens flare here what i'm going to do is create a new layer by pressing ctrl shift and n or you could just press this little icon here the plus icon inside the square to create a new layer i'm going to use the spot removal tool sample all layers is ticked that's quite important and just going to paint over this lens flare here that's actually a pretty good job do that a little bit there check the rest of the image now i don't like having very bright distractions on the corner of the frame see how much they draw the eye they're very distracting so i could crop the image or you could just use the spot removal tool to get rid of them and that's far less distracted now and yeah i would just go by editing this image as i normally would if you wanted to use a star tracker for example for the sky exposure do the focus stacking first and then blend the sky exposure on so you still want to make sure that you've got a an image that is focused to infinity in the focus stack but replace that with the tracked exposure later on if you want you can also incorporate stacking into your focus stacking so when you're focused at infinity you can take eight exposures stack those for noise reduction and then change the focus to be closer in the foreground take another eight images and focus stack that so in that instance you do the focus stack of each individual frame first then you do the focus stack so you can incorporate different techniques into the focus stack if you're doing stacking do it before the focus stack if you're blending a sky on do that after sorry the focus deck anyway i hope you've enjoyed today's video guys i hope you've learned something make sure to hit subscribe because there are plenty more of these useful videos on my youtube channel and if you go now to enjoy the night sky anytime soon i wish you good luck increase guys [Music] you

Channel: Alyn Wallace

Views: 63,355

Keywords: astrophotography, focus stack, stacking, nightscape, milky way, night, low light, astronomy, photography, tutorial

Id: KLbgl7fZmgc

Length: 19min 19sec (1159 seconds)

Published: Sun Jan 23 2022