Plenty of negative LCD Casio models are worst. My personal worst are 6900 negative, AQ164W negative, AW591 negative.
SGW100 indeed has lousy angles but it's not bothering me to the extent of negative models.
Best f105/108 Nixon and Timex 50 lap full size.
For sure Samsung Galaxy Sport with OLED takes a win. That thing is 180 viewable.

 

My personal worst are 6900 negative

Dang I just bought one and it's on the way

 

My best digital for contrast and viewing angle is the Casio B640WD with the 3294 module. Background is light, characters are inky black and the viewing angle is the longest I've seen.

 

Totally agree. I have the B640 as well and like it a lot. Menus operations exactly like the DW5600E.

 

Out of my many, this is one of my best viewing angles piece. The case is a T5E901, but the module is from a T5E931. In the T5E901 I have seen hit/miss for viewing angles (some ok, some very bad).

 

I dont have it anymore but my protrek prw3100 with STN display had the best viewing angle. Basically as long as you can see the screen, you can read the time, regardless of angle.

 

3100 - STN
GW2500 (not sure what it is but it darn good)
Are examples of good inverted screens.
3100 is almost as good as positive. Angles excellent and despite been negative you can use it in dim lit room because STN has higher contrast.

 

The CASIO module 3234 display almost disappears at some angles so I replace it with the almost identical movement from an SKMEI 1337.
I took these photos after a swap, so the CASIO movement is on the left.

 

W96H a nice one with the timer mod, the viewing angle could have been better though.

 

What reasons make different models' screen quite different? Is it because of different supplier of these screens that diff models have different qualities?

I don't think it has to do with cost since some of the very inexpensive ones like the F108 have excellent screens.

 

What reasons make different models' screen quite different? Is it because of different supplier of these screens that diff models have different qualities?

I don't think it has to do with cost since some of the very inexpensive ones like the F108 have excellent screens.

different reasons it's from electronics around, voltage control, screen build quality and frankly your luck.
Different types of screens have inherently different angles. STN, MIPS, LCD (there are several types of them among what considered just LCD), E-ink, OLED all have different inherited angles, different maximum attainable contrast etc.
Different screen thickness, voltage fed to non working elements, quality of manufacturing, design (size of elements, placement, tint/ no tint) etc. sets it apart in non type thing.
Angle itself is not full story for legibility but here we talking about angles.
there are technically 2 types of problems:
1. you see all elements
2. you stop seeing "working" elements.

With #1 been #2 plus extra. So things are complex and there is no singular answer to it.
F108 does not have way better angles than some other watches but it don't show non working elements and bold font create good contrast coupled with minimal distance between LCD and "crystal" create great visibility. so it's not exactly best angles but other factors making it more legible.

 

Garmin Instinct Solar. MIP or GTFO when it comes to overall "all lighting" contrast and viewing angles. The bezel obscures the screen before the viewing angle does.

STN displays came out in 1983 and are a complete joke compared to MIP displays. STN is no more expensive to manufacture than a "traditional" LCD; boggles my mind when I hear folks talking about it (especially on the G-Shock forum) as if it were the "future". Proposing STN displays as the "future" seems, at least to me, like a horse saddle manufacturer proposing their new riding tack as the "future" 10 years after everyone bought a Ford Model T. Sorry, but we're all done with that, why not join us in the new century Casio?

Here's the Wikipedia entry for STN for anyone who's been asleep since 1983...

Super-twisted nematic display

 

These are great at all angles, I like the retro frosted lcd on the Omax, but the 'Casio Royale' probably has the worst view at an angle.

 

Mips requires more processing power compared to regular or STN LCD alike.
Simply there are more elements to control and keep in memory. Not a huge deal in 2021 but ...
This is sufficient to keep seeing LCD only watches. Garmin, CASIO GBD and such are not watches per se. They are lower grade smartwatches. I feel bad about calling Instinct lower grade so let say more simple and monochrome.
If you think about it why not OLED? Because it will require even more processing power each pixel has color information to it. While regular F91 ish LCD has 30-40 elements to control Garmin Instinct has 40000 or more.
Not a big deal but most of digital watch tech has not changed since 80s. It's as conservative as mechanical watches in this regard.

Also not all MIPS displays created equal.

 

I think you may need to investigate further about MIP displays. Here's a quick explanation of one of the manufacturers of these displays for sports watches like those manufactured by Garmin [Emphasis mine]:

Memory-In-Pixel (MIP)
With a randomly accessed stored bit per pixel cell structure, you address pixels individually, refreshing only those pixels which need to be changed thereby reducing power requirements.
The extremely low power LCD cell structure design makes these displays excellent candidates for battery powered applications, such as wearable medical devices, wearable sports gear, Internet-of-Things products and other portable applications.
The KYOCERA MIP technology provides:

• Ultra-Low Power in Static Mode
• Low Power when Changing Images
• Contrast Ratio > 24:1
• Reflectance > 17%

More Information

• Contact a Distributor
• Locate a Sales Rep
• Request for quote

(Source link: Kyocera Memory-In-Pixel Technology)

The transflective MIP LCD displays used by Garmin, both color and gray-scale, are an excellent constant-on low power display choice which contributes to long device battery life - weeks instead of days.

HTH

 

I personally can't believe oled ever made it to the watch world. Doesn't seem right to even call them watches when you can't tell the time of day most of the time they are on your wrist. Currently the sacrifice of color is worth it to be able to read a watch from angles, distance and at all times. Not to mention battery life. Really doesn't matter to me how old the tech is.

Just got an instinct and really liking it so far.

 

Just arrived in the mail. Casio ws1000h. Very nice features. At within-range viewing angles nice contrasting legible display, but soon everything disappears at a higher angle...

 

Garmin fenix 6xPro with color transflective MIP LCD:

Display can be set for either positive or negative at will. I'm impressed.

 

TX HydroMod!

not bad for a negative display

HydroMod by Wolfsatz, on Flickr

G Shock by Wolfsatz, on Flickr

Full Sun on Dial
GIT by Wolfsatz, on Flickr

Indoor Shot
GIT by Wolfsatz, on Flickr

G-lide ing through a car wash
Tickers by Wolfsatz, on Flickr

 

TX HydroMod!

not bad for a negative display

HydroMod by Wolfsatz, on Flickr

G Shock by Wolfsatz, on Flickr

Full Sun on Dial
GIT by Wolfsatz, on Flickr

Indoor Shot
GIT by Wolfsatz, on Flickr

G-lide ing through a car wash
Tickers by Wolfsatz, on Flickr

I have the same Timex with +ve display. That watch is very nice feature packed and one of the most comfortable to wear. Did it come with -ve display or you swapped the module?

 

Got this one a few days back - casio ws2000h (step tracker). Similar poor angle situation (a bit further worse). The lap/split feature with the added option to view current time with lap/split time and also current lap number is very nice on this one. Misses on SNZ alm, auto repeat timer.