^^^ This is true for me as well. Xbox view for some shots is almost useless, but they look fine on the computer or phone.
Consider how we use laptops and mobile phones.
Mobile phones particularly, used outdoors, lots of glare, typically most people set their phone brightness artificially high (many scenarios tho and sometimes people will use auto-settings which mean it changes). Also phone screens are smaller so the res will look far sharper.
Laptops and computer screens - all depends on make / monitor / screen type but much as lots of Home Hi-Fi's have artifical "true-bass" or different preset EQ settings meaning most people won't listen to music how it was recorded / produced but rather they will listen to it tweaked to their own tastes, meaning engineers usually go for a rich, clear, but relatively flat response which will sound good across a range of possibilities (including room acoustics / system type / context etc). It's the same for screens , TVs and monitors, all of these settings are to artificially enhance what you are seeing but they don't reflect the true media.
I suspect game developers do the same- knowing some people will have different backlight / colour / contrast / brightness / res settings - they probably go for somewhere in-between and set it all a bit flat knowing that many people will fiddle with the settings to their own taste.
But this is the thing - when you do that, you aren't seeing how the game actually looks, and therefore unless you have "flat settings" you never know exactly what you are seeing in terms of what the game is putting out.
I checked my recent screen-shots across 4 different displays yesterday - the pictures all look different, because I have different display / contrast / backlight / settings on all. On my old laptop the pics look really washed out because the brightness is far too high and it has a dell specific preset which I find helpful for certain things, I use this for design / print stuff a lot and it helps me to spot certain nuances but I have to print stuff out and compare on a more balanced screen before I go to print knowing that what I'm looking at is slightly artificial and intended to help me spot things I wouldn't see on a truer screen (if I was working in a design office it would be very different but I work from home on that stuff and don't have the same resources). For music, it's different - I write and edit at home on flat (ish) monitors but the room isn't acoustically treated, so I have to go into the studio into a deadened room with incredibly flat monitors to mix and master. Following that, I go into a bright room with a PA and listen again before I sign off - if it sounds good across that / laptop speakers / phone speakers and then finally hi-fi speakers. I also use EQ to do things end users would typically do like boost the hell outta the bass to ensure it's not going to sound distorted the minute someone puts on their "jazz" or "rock" or "dance" settings on their hi-fi meaning that sometimes I'll dip the sound at certain frequencies and not make them overbearing before the end-user gets their mitts on it.
As I've also said - my screen shots also look different in terms of brightness depending on wether I've taken during the afternoon or at night (when my TV is the brightest thing in the room).
So again - I'm not surprised that with all these sorts of perception and user setting type things going on that there is a variance (I'd be very wary of "game-mode" settings on monitors as that's one manufacturers idea of "game mode" but who is to say that this setting doesn't artificially sharpen or increase contrast / warm up the colours or whatnot (because that's exactly what game mode does on my LG screen so I have it switched off and the settings far more balanced while taking screen-shots).
That said - yup, I've noticed a few that were very, very dark in comparison, so there's even more at play here - dusty may have a point about how light is rendered but I haven't got a clue on that sort of thing I'm afraid but what I can tell you is that compression can and does tend to have an effect on lighting / particle effect type stuff etc which is why if I design a leaflet with a nice smooth gradient fill or a glow , then sometimes going through different compression algorithms can mess this up.
Final thing - for anyone editing / posting from mobile phone - you just can't expect things to look as good on a bigger screen, just ain't gonna happen, mobile phone is the most artificial way of seeing things IMO, I'd look at your images after editing on a computer / screen and once done, you should find your screenshot looks EXCEPTIONAL on a mobile screen, but going the other way is a recipe for disappointment.
Lots of things at play here, I must admit I know more about sound / perception from that level which is why I refer to that (hope it's not confusing) but knowing that hearing and how we see things both have a lot of variables, it's natural for me to try and compare
That said - peeps be getting great screenshots regardless and a little bit of messing with photoshop (or any simple photo-editor really)is all it takes if it's a bit dark (bearing in mind that photoshops algorithms are going to be far nicer than soomething cheap and nasty but for the most part, the layperson won't spot it).
Right, said enough about this - back to some exploring methink, happy screenshot hunting friends

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