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Allow me to explain the question which might seem slightly vague.

One particular use case where i generally face this question is when i am shooting something during nighttime, dark conditions. In these cases, when the scene is too dark for autofocus to work properly, i generally go to another area where i have some other well lit object at a similar distance and then use half shutter press to focus on it.
Now, since i have the focus set to my preference , i go back to my OG subject and then hold the AE/AL button (it is set to AE/AF lock) and take a picture. Now, i may not like the picture, so i might change some setting in the camera. Do i now have to go back to the well lit object to set focus again, or can i just repeat the same thing after changing settings, and just take a second photo while holding the AE/AL button again ?

Now i know, "changing settings" is too broad a term. There are a hundred settings that can be changed. So, i am trying to divide them in my mind, into different levels of settings .
Level 1 : Changing image quallity ( norm, fine, basic) , size , picture mode ( standard, vivid etc.)
Level 2 : Changing PSAM modes, changing shutter speed, ISO , exposure comp etc.
Level 3 : Everything else, more indepth settings, in the camera shooting menu etc.
Level X : changing aperture ( i feel this HAS to be changing the focus, so i put it in separate level, correct me if i am wrong )

Now, i understand these levels are just imaginary, there might be different things in different levels that do need me to autofocus again, and some that do not. But is there any standard rules that most cameras follow regarding which settings can be changed without affecting the focus and which will need me to re-autofocus again ?

Also, one of the suggestions in the comments about turning off autofocus completely, makes good sense. So, if i autofocus once, and then turn off Autofocus, can i be assured that as long as i do not mess with any focus setting ( e.g. AF-C, AF-S etc. ) or manual focus ring, the focus will stay where it was ?

Which settings affect the focus distance and will need me to focus again, and which can i just change and click a picture without having to focus again ?

I tried looking at the manual , but what keyword should i be searching for in the manual ?

I use a NIKON D5600 with a Nikon AF-P DX nikkor 18-55mm 3.5:5.6G VR lens

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    Why not just switch off autofocus altogether if you want to ensure it doesn't change?
    – Philip Kendall
    Jul 11 at 15:04
  • @PhilipKendall I was under the impression that switching off autofocus only means that hitting the shutter halfway wont affect the focus . That is not the issue i have. I am not touching the shutter halfway anyway . The only things that i am worrying would affect my focus is going into the settings, changing PSAM mode, changing shutter speed , etc. Jul 11 at 15:09
  • @PhilipKendall But i guess, you are saying that turning autofocus off will prevent those other things i mentioned from changing focus as well. If that is true, then i will definitely give that a try. But can you confirm that, with autofocus turned off, changing aperture wont affect focus either ? Aperture seems to me to be directly linked with focus. Jul 11 at 15:24
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    Even with the small edit, this is still a very confusing question. If you're using back button focussing, then the half-squeeze is irrelevant [& already disabled]. Also, tbh, if you've time to mess around in the menus before taking the shot, you've time to refocus.
    – Tetsujin
    Jul 11 at 16:18
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    Please do - please also clarify exactly how you are using the focus mechanism… & why your focus length is not the to the object you are shooting.
    – Tetsujin
    Jul 11 at 16:36
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None of the settings you mention will change the lens focussing - but changing the focal length on a zoom lens definitely will.

Late edit
Now we know what lens we're talking about - the kit 18-55mm, even changing focal length isn't going to me much of a problem with that lens. Almost by accident of design rather than by intent, it's almost parfocal anyway [it doesn't change focus based on 'zoom'].

After some further clarification in the question body - the OP is using AF Lock, rather than back button focussing, 'AF ON'.
Aside from the above, that nothing except changing focal length will really affect focus, it would seem the solution would be to use AF ON [or the other two manual focus alternatives below]. Instead of trying to use the button as an override, use it to focus when needed.


Previous answer, partially obviated by comments & question edit
This is almost moot unless you switch off the AF mechanism in the half-press by one of the following methods.

With standard settings, every time you half-press it will refocus, so anything else you do in between will require another half-press, focus, shot. You have apparently been overriding this using AF Lock.
Otherwise, you cannot avoid the half-press no matter how fast you do it, it will check or refocus every time you press it, unless you switch it off.

The way to avoid this is by using back button focus instead, so only pressing the back button will focus, pressing the shutter will simply take the photo.

You can set this up in settings - I also moved mine to the Quick menu to save having to dig for it every time. You can lock focus &/or exposure, jointly or separately. This is from the D5500 manual. I doubt the D5600 is much different…
To clarify, after comments & question edit, 'back button focus' is termed 'AF ON' by Nikon. This is then the only button that will instigate focus. Using AF Lock is an override, only active whilst the button is pressed; otherwise standard half-squeeze will initiate focus.

enter image description here

Alternatively, if your lens supports it, you could just flip the physical switch on the side from M/A to M.
If not, you can disable it in the main shoot menu on the rear of the camera.

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  • I DO use the back button focus. So, i set the focus to, say infinity, then take the picture, using back button. So, now if i go and change the aperture, shutter , ISO etc. , are you saying that i can take the 2nd picture using back button without having to once again focus to infinity ? If i am understanding you , then that is what you are claiming, right ? Are you sure about the changing aperture part ? That really makes me think , will change the focus Jul 11 at 15:15
  • I wish you'd mentioned that in your question, rather than only mentioning half-press. Would have saved me a whole lot of effort looking up where it was in the manual.
    – Tetsujin
    Jul 11 at 15:16
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    After the clarification - that's not back button focussing, that's AF Lock, a different thing.
    – Tetsujin
    Jul 11 at 17:26
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    @silverrahul Back button focus means you press the rear button to focus, not to lock it. When you release the back button, your focus will stay locked. Pressing the shutter release or changing settings will not affect focus. There are a few ways of setting up BBF which you need to sort out for your shooting style. There are many web sites that show you how to set up BBF.
    – qrk
    Jul 11 at 18:36
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    @K.Minkov - now we know which lens it is, the kit 18-55, it's as near as damnit parfocal anyway… almost by accident ;)
    – Tetsujin
    Jul 13 at 11:24
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Changing focus may not be the issue. If the aperture changes it will affect depth of field, so part of your image may go out of focus. This will be more apparent at the telephoto end of the zoom range.

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