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Galaxy S IV - Screen, display, auto brightness, etc explained

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Slade8525
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Default Galaxy S IV - Screen, display, auto brightness, etc explained

As it seems there are a few threads on auto brightness and color issues, i figure i should do the best i can to explain how it works on the S4, and mobiles in general. I work in Television/Film and have been shooting for almost a decade.

ANY QUESTIONS, feel free to PM me, i'll probably ask for very specific photo's (ISO/WB and other data) so i can help you in a professional manner, and i'll try to reply within 6-8 hours. No one should live with a bum screen!

To fully understand what im trying to express, load the attached image onto your phone, and on a bright sunny afternoon, print out the attached image on a small piece of decent photo paper, grab your phone, and find a room in your house that has only fluorescent lights and close any windows or shutters.

Look at the photo in the sunlight; note the colors. Now go inside to the fluorescent dark room, note the change in what the colors look like, and that white is still pretty white (thats your brain), then turn your camera flashlight on (LED), and note the changes in color again (some reds may look purplish or greens bluish), but white still looks kinda white (should look very light blue). Now repeat and look at the print out versus the same image on your phone screen; it should match best under 6500k lighting, but still be off (thats a printed image vs monitor thing though). Also depends on your printer ink type (dye/pigment), color space, etc etc etc. Your eyes take raw data in, but your brain does the magic, and says 'nope, thats white', so you perceive it as 'white' or 'white enough' and you 'know' it is meant to 'represent' white.

Hardware - This includes an ambient light sensor. The way these work is similar to metering systems in cameras; they measure the amount of light hitting a photodiode. Even in high end (DSLR) cameras, sometimes the light meters are junk. On cell phones, they are typically pretty crappy. The iPhone 5's have excellent ALS (ambient light sensors) and they ramp up/down smoothly; much better than any other device i've used.

The way the ALS works in most devices is simple; there are several photodiodes, each tuned for a specific spectrum of light. Say two for 3200k, two for 6500k, two for whatever else, etc, and they basically average the reading, apply a curve, and adjust the screen appropriately. They do NOT accurately measure color temperature very well, and 'see' brightness only in limited spectrums, meaning their idea of what 'bright' and 'dim' is may be vastly different from the human eyes' perceived 'bright' or 'dim'. Also, the 'curves' applied don't match up that well with how the human eye perceives brightness; its really amazing we can fake it as close as we can, really, but most of the magic lies in your brain.

Lighting - this is kind of tricky; and i don't feel like getting into it too deeply, but what you perceive as 'white' is mostly dependent on your brain; not your eyes or the lights around you. Think about reading a book (a real book) inside a library under fluorescent lights; the pages are white, even though the color temperature might be 5000k or 6500k. Now that same book outside; thats 5800k. Now under some old incandescent lights; that might be 2800k. Yet you know it SHOULD be white. Thats your brain. And thats reflected light; its based on the ambient color temperature around you; so reflected light 'looks' white or blue or whatever.

Your phone screen (galaxy S IV) is basically white balanced at 6600k , so it will appear most white when around lighting around 6500k, which is on the bluer side of daylight/cloudy and indoors.

Screen Mode - The Galaxy S IV has a feature that allows it to dynamically change based on the ALS, or can be overridden by the user, which mostly affects color gamut, and either amps up contrast and saturation while shifting hues slightly, or flattens them to a more realistic (usually most people prefer high saturation/high contrast images) image.

Sampling frequency - i have no idea what the ALS sensor samples at, or any definitive specs on the exact sensor and how it interacts with auto brightness, its priority, etc (yet, ive emailed Samsung and i wouldn't mind coming up with a simple app to adjust this if i can figure out the sensor specs and their software). But certain lights (fluorescent mostly) flicker at either 50hz or 60hz depending on their AC current, which may, at times, interfere or give bad readings to the ALS depending on the ALS sensor reading timings (again i do not know exactly what those values are, i suspect they are long as my S III and S IV typically react about a half-second behind lighting changes).

DETERMINING IF YOU HAVE A BAD DISPLAY

All together, it works pretty darn good, if a bit slowly, but there seems to be a lot of confusion and people wondering if their screen is bad. The BEST and EASIEST way is to go to any cell store or mall, and compare YOUR screen and the SAME image to another S IV, with the same settings. The best settings for this are to turn power saving OFF, turn off ALL power saving apps, turn auto brightness OFF, turn brightness up ALL THE WAY, go to 'settings', 'display', 'screen mode', and change the setting to 'movie'. Compare several IDENTICAL images or pages. Then change the 'screen mode' to 'standard' and compare the same images.

While doing so, be sure to check out images such as the one i provided and make sure the colors match, grays are grays or at least the same slight caste of pink/green/etc, and while doing so, TILT THE SCREENS at various angles together (level surface, side by side, tilt to 45 degrees at the same time on all 4 axes), and look for discoloration or bleeding; if you see big differences between two or three other phones and yours, you got a bum screen. I haven't seen a 'bad' one yet, and i made the poor AT&T guy open up five of them and let me play with them (AMOLED also has jet black splotches with full blacks in a fully black room; i wanted the screen with the least noticeable splotches).
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'01 Nokia 5165 - '02 Sony Ericsson T61
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'07 ATT Tilt/HTC Kaiser - '09 iPhone 3G
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'13 Samsung Galaxy S IV


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jetlitheone Old
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Thanks for this. Question though. When I pull my keyboard up to type on something or if I'm in a YouTube video and I tap the screen to bring up the progress bar the color shifts dramatically. I've tried many settings and it always does this. Also tried it on another s4 multiple ones did the same thing...

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rapaholic999
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Just hoping for a fix for it
The white balance can actually be calibrated by changing the calibration levels of the LEDs sitting under the screen
Lets hope for the best
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Slade8525
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Quote:
Originally Posted by jetlitheone View Post
Thanks for this. Question though. When I pull my keyboard up to type on something or if I'm in a YouTube video and I tap the screen to bring up the progress bar the color shifts dramatically. I've tried many settings and it always does this. Also tried it on another s4 multiple ones did the same thing...

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ok, do me a favor, I would prefer if you had either a prosumer camera you could use, or better yet a DSLR you could borrow that i could guide you through how to take two shots of the differences with all the important variables locked down so i can figure it out for you. I believe the screenshot feature ignores the 'Screen Mode' settings, as it should (you wouldnt want a screen mode dictating recording colorimetry options), so it does require real photos to figure out.

Have you changed the standard 'Screen Mode' setting or left it at 'Adapt Display' or 'Dynamic'? Those will keep changing it; Professional photo and movie are more flat, but they do not change. Again disable power saving mode, power saving apps, turn off auto brightness, (in this case set brightness to where you want it) and check it out again; if it doesnt change colors, (which it should not), you have no issues; its a normal 'feature' of the device. The idea is to limit all variables. Try that and PM me the results. If the colors no longer shift, the issue was 'adapt display' or 'dynamic' Screen Modes. Auto brightness/powersaving mode/power saving apps should only affect brightness; we are only disabling them to limit perceived changes.

To try to trouble shoot this, change screen mode to a static setting like 'professional photo' or 'movie' in Screen Mode and turn off auto brightness, turn off power saving and turn off all power/battery saving apps/etc, bring up a Youtube video and play it, then bring up your keyboard and see if the color shifts (it shouldnt if you have changed Screen Mode to Pro Photo/Movie and disabled powersave/all battery apps/auto brightness). Then let me know if that fixes it via PM.

Quote:
Originally Posted by rapaholic999 View Post
Just hoping for a fix for it
The white balance can actually be calibrated by changing the calibration levels of the LEDs sitting under the screen
Lets hope for the best
problem is most calibration settings/programs and methods i know of are non-pentile and are mostly software fixes for what ive used; AMOLED is different PenTile (RGBG) than what i tried to fix before which was Motorola Atrix 4G PenTile (RGBW, red green blue white), CCFL LCD is way different (more what im used to, as well as LED LCD and even IPS is easier as it is still RGB), and all the curves software etc are all proprietary to manufacturers. Granted controlling just the R/G/B/G LED's would help, but getting the curve right and correcting might take longer than the Galaxy S V arrival. I spent months calibrating all my gear; most of it is 2-3 years old, and at least 6-12 months old before i get it all settled and can rely on it for a given job. Usually i rely on calibrated displays, knowing my own color limitations, RGB histograms, vector scopes, etc (i have a very slight red/green color weakness, but extremely sharp vision and i know how to work around my limitations).

I actually emailed Samsung about this for as much information as i could get (not much so far but im digging). I have a friend playing with LUT curves on his S IV and he says its a close second to the iPhone screens for AdobeRGB in 'movie' mode, which i happen to agree with; its pretty flat, but the contrast on greens is still high, which again is a PenTile RGBG specific issue; we are both vets of backlit RGB panels. My friend also works with the same company i consult/represent; it took him almost three months to properly calibrate LUT curves between a single sensor and a simple 480P CCFL LCD display, and that was with full manufacturer support. Colorimetry is a science.
'01 Nokia 5165 - '02 Sony Ericsson T61
'03 Nokia 1110 - '04 Nokia 3200
'04 Sony s710a - '06 ATT 8525/HTC Hermes
'07 ATT Tilt/HTC Kaiser - '09 iPhone 3G
'11 Motorola Atrix - '12 Samsung Galaxy S III
'13 Samsung Galaxy S IV


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dgfriedl
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Originally Posted by jetlitheone View Post
When I pull my keyboard up to type on something or if I'm in a YouTube video and I tap the screen to bring up the progress bar the color shifts dramatically. I've tried many settings and it always does this.
Same here. Thanks for the write up but I'm seeing the same thing.

I dim the display with the Screen Filter app for reading in bed and whenever my keyboard pops up (SwiftKey, TouchPal or stock) the entire screen gets a green cast. Under these conditions it is very dramatic.

I use manual brightness and turned off the Autoadjust Screen Tone setting

Some other apps exhibit a fluctuation in color cast when I put my finger near the screen which is double weird. :-\

-darren

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jetlitheone Old
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Yes it's weird I don't know what's happening. Anyways I'd toy turn the brightness up past half way the color cast goes away. .. Not sure what it is

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MrPlNK
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If you go to a settings menu and scroll up and down fast, my phone gets a purple tint and leaves like a shadow of the words behind... Kinda annoying.. Anyone else notice this?

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Yes smearing

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Slade8525
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Quote:
Originally Posted by MrPlNK View Post
If you go to a settings menu and scroll up and down fast, my phone gets a purple tint and leaves like a shadow of the words behind... Kinda annoying.. Anyone else notice this?

Sent from my SAMSUNG-SGH-I337 using Tapatalk 2
thats because AMOLED usually have a slower response time, upwards of 20ms

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Yes smearing

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yep, i have some old LG CCFL LCD monitors with a claimed 2ms (more like 6-10ms) response time from 2006; they were about $300 each back then. i also have a new IPS with 30ms response time; it is annoying.

also some pentile displays are slower between subpixels; my Atrix 4G had very slow blue white pixels (RGBW) so you had a weird dimming as well when scrolling through texts.

Settings, Display, disable Auto Adjust Screen Tone' as well, its a power saving thing i forgot to mention in the first write up.
'01 Nokia 5165 - '02 Sony Ericsson T61
'03 Nokia 1110 - '04 Nokia 3200
'04 Sony s710a - '06 ATT 8525/HTC Hermes
'07 ATT Tilt/HTC Kaiser - '09 iPhone 3G
'11 Motorola Atrix - '12 Samsung Galaxy S III
'13 Samsung Galaxy S IV


ATTN: AT&T UPDATE UCUMF3 KILLS ROOT, ODIN, AND CUSTOM RECOVERY/ROMS
jetlitheone Old
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thats because AMOLED usually have a slower response time, upwards of 20ms



yep, i have some old LG CCFL LCD monitors with a claimed 2ms (more like 6-10ms) response time from 2006; they were about $300 each back then. i also have a new IPS with 30ms response time; it is annoying.

also some pentile displays are slower between subpixels; my Atrix 4G had very slow blue white pixels (RGBW) so you had a weird dimming as well when scrolling through texts.

Settings, Display, disable Auto Adjust Screen Tone' as well, its a power saving thing i forgot to mention in the first write up.
it can be fixed with color adjustment though so maybe a software update can fix it as well

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