I am both a newcomer to UHH and an amateur who wishes he knew more. I've been taking photos since 1966 and did some fairly good B&W work back then. I customized the Adams Zone system to work for me with 35 mm B&W film and polycontrast paper. I built my own darkroom densitometer for spot readings of projected negatives. That's just to explain that I'm neither an expert nor a neophyte but something between. I'm fairly new to digital photography so some of this is confusing me.

The noise in a given sensor's output in a given shot is the result of many possible factors but the most obvious and perhaps the most influential is the "gain" applied to the pixels which have a natural sensitivity that does not change (seems to be ISO 100 on most of the cameras I've looked at). It makes sense, then, to reduce the need for gain as much as possible. So the way to do that is to hold the ISO down and use some combination of slower shutter or bigger lens opening, where available. The limit on this is that the brightest "zone" that should contain "information" should be given no more light than the sensor can handle. In this kind of example, the constraints are the available light and the available lens opening. The practicality of shutter speed enters into this in a similar way. I don't see how any of this is at all in doubt. So that is question #1.

Question #2 is overlapping: what is the practical difference between ETTR and giving more light with lens/shutter combinations? Does any of this change the value of keeping ISO as low as you can?

Technique: Although my camera is able to do very good auto exposure, I find that I need to use shutter priority when photographing birds or any critter that's likely to move. Yes, my Sony lens is ver well "stabilized" but I feel that I need at least 1/400 sec. to get the picture that freezes motion. When I use a legacy lens I manually set both shutter and lens opening and let the camera work with ISO. With the legacy lens at 300 or more mm, I need 1/800 second for camera movement as well as subject movement. YMMV.

Some of the replies imply it, but I want to specifically recommend the "Ding" Darling refuge on Sanibel Island.
https://onedrive.live.com/?authkey=%21AHwBNAMtBhmkENc&id=5DEF67F4664CEDAE%216804&cid=5DEF67F4664CEDAE
I'm not be best at this but the photos should give an idea of the birds and other critters to be found there. If you have a Senior pass for federal parks it works there. It's a 4-mile paved drive, one way and a birder's delight.

Also, I just bought a Sirui P-326 monopod from B&H which is really, really good, under a pound and only 15" but long enough extended for my not to have to bend down. I'm about 6' tall.

Although I use a Sony a6000 and will soon upgrade to an a7R II, my wife uses a Nikon Coolpix P600. See if you can tell the difference on the pictures linked above. That Nikon is fantastic for birds and the P900 is probably even better, uses a lens with equivalent reach of 2,000 mm! You can't even buy a decent lens for the Sony for what her camera cost and there were many shots she could get that I could not.

If you believe the built-in protection in Win10 makes supplemental protection superfluous you are saying the opposite of the vast majority of professional reviewers, many of whom use the standard Win10 protection as the bottom of their acceptable set of results when testing. If that argument fails, then the contention that there is zero evidence that Macs are better in that regard must also fail. Use Windows if you like it, but please don't lead the unwary into the weeds.

I am a newbie and this is my first contribution. There are many expert opinions above and I do not mean to contradict anyone. What relatively little photo work I've done on the computer (3 different computers - 2 Macs and a Win10) convinces me that first and foremost you need a fairly large monitor and it has to be able to correctly display your gamut, gamma, etc. I have worked for hours on a photo on my Mac-Mini which drives a (I think) pretty good HPZR2440w monitor. I've put some time and effort into getting its calibration right. I've even measured the color temperature of the images with an app on my iPhone and tweaked it a bit for that. When I look at the same pictures on either the other computer (good Dell monitor) or, worse, my MacBookAir 13", the real quality I created just doesn't show up. And, of course, a TV is not going to be satisfactory as a monitor (not familiar with =>4k, though).

So point 1 is the monitor. Your work is wasted if you are not seeing it on a large enough, good monitor that is correctly calibrated. For me, 24" is minimum and larger would be better, but I don't have one yet.

Point 2 is the application(s). I am still using a few of them and some work better for me in some cases, others in other cases. Of course, that is dependent to a large degree on my camera's RAW format (Sony ICLE 6000) and the way that some programs read the RAW files. On the Mac, "Preview" and "Photos" work well. Sony provides a RAW to ?? converter that sometimes is terrific because it can emulate the camera's scene choices. Then there is RawPhotoProcessor64 which is only for Mac. I'm sure the Sony program has a Windows version. Of course, Preview and Photos on the Mac are only for the Mac. And lastly there is Lightroom for which there are both Mac and Windows versions. So point 2 is to have the tools to work with the RAW files to your comfort and satisfaction. I've found that the Mac-Mini (with an I7 processor and 16GB of RAM) has sufficient power but the MacBookAir (2011) does not. My Windows computer is a recent build of my own parts selection (gaming level stuff) and has a lot of power but I have not used it for editing.

Your camera will not be the same, in many cases. So your findings will likely be different. I hope that I've put the computer question in perspective. My personal preference is Mac and I am quite familiar with both Mac and Windows. But they are both good operating systems for a huge variety of applications and it's the applications that matter (along with what you do with them).

Any brand and any OS can provide the processor power and the necessary RAM. They have to be powerful enough, but power alone is far from sufficient. I've ignored Linux even though I often suggest it in other situations. That's merely because I suspect that the applications are not as complete a set of choices and abilities. The hardware is the same as for Windows so that's not an issue.

Get the best you can afford, too. You spent a lot of money, probably on camera and lenses. Many of us spend a lot of money going places to find photo opportunities. By comparison, the computer is cheap. I hope some of you will find this helpful.