Issue with images captured by Android Phone

[RonB1949]

I am finding that most or all the photos I'm taking with my LG K51S phone need to have their gamma corrected when I upload them. Before correcting, they look sort of 'misty' but after correcting to 0.60 gamma using IrfanView, they are fine. I can post images if required.

I have tried using the built-in camera app but I use Open Camera normally. Both give the same results. There doesn't appear to be any setting for gamma in either app.

Thanks in advance.

*Edited by admin to remove font/colour options so the post is readable.*

[Tannin]

Hi Ron. You are posting black text on a dark grey background. It is very difficult to read. Most likely you have selected a different AP colour scheme (one with a white or light-coloured background) so it looks OK to you, but most people using the site use the standard AP scheme (white ext on a dark grey background) and can't read your post. I recommend using the default colour scheme to make things easier for everyone.

On to your query. I don't use phone cameras (well, practically never) but I would look at two possible causes:

(1) Exposure compensation. If you have any exposure compensation set, everything will be too dark. (Or too light, depending on how you set it.)

(2) White balance. Incorrect white balance does weird stuff. To start with, set it to "auto". (There are better settings, but auto is a sensible start.)

(3) Colour space. Do not use Adobe RGB! Set both phone and computer to SRGB (if they aren't already). Adobe RBG produces horrible colours. (It does have a useful role, but not a relevant one in this context.)

OK, so that's 3 things. Good luck!

[ricktas]

Hi Ron. You are posting black text on a dark grey background. It is very difficult to read. Most likely you have selected a different AP colour scheme (one with a white or light-coloured background) so it looks OK to you, but most people using the site use the standard AP scheme (white ext on a dark grey background) and can't read your post. I recommend using the default colour scheme to make things easier for everyone.



Hey Tony, that happens when the text is cut-n-paste from another website or a word doc etc. Just for info. I will edit the OP post to fix it.

[ameerat42]

Hi, Ron.
Check your settings, including those that Tannin indicated.

I take it you're shooting just in jpeg mode and not some sort of
"raw" format (usually DNG on phones)? In cases like these, it's
good to post a shot illustrating the problem - with the EXIF data
intact, and perhaps an "after" shot of your processing.

I checked the LG site and gsmarena for info on this phone's camera
but it didn't say whether the model can shoot raw.

Welcome to AP.

[RonB1949]

Thanks for the posting fix. It was a cut-and-paste.

- - - Updated - - -

Thanks. Here is a shot without, and with, the gamma fix148640148641

[ameerat42]

OK, the attachments were not successful. Have a look at the post
below for how to do it...

http://www.ausphotography.net.au/forum/showthread.php?156515-Attaching-Images-To-Posts-On-AP

[RonB1949]

These are the before and after gamma correction images.

148651148652

[ameerat42]

Hmm...! DULLsville, alright, and I don't mean the Balgowlah shopping centre.
Your camera image shows a tonal flatness (your misitiness) and low saturation.

The processed version is only a minor improvement, and I don't mean that you
lack processing skills. I think you've got some challenging output from that
phone cam.

I take it then that these are out-of-phone jpegs, and...
...
I've looked up the picture-taking settings for the phone... - there aren't many.

Two things about Open Camera:
- it can't give you what your phone does not have;
- and anyway within this app you should select Settings-Camera API-Camera2 API
(the alternative is "original camera API", but that's used by the native camera app).

In whichever app you can access it, find Scene Modes and try a few that are NOT
"Normal" or "Standard".

Going back to one of your original questions about gamma settings, look for a Manual
mode setting. In the Open Camera app, press the square icon that contains the -/+
symbols. I don't know how in the native app.

And referring to one of Tannin's qs: the Exif in the posted photos DOES show sRGB
and Auto WB.

Finally, I've tried Irfanview to simulate your processing, and also Photoshop, and even
another freebie called Faststone Image Viewer. - A challenging image in all three.

[Tannin]

Excellent!

The issue here is exposure compensation. That is easy to fix.

I checked your EXIF information and everything else is OK.

* sRGB colour space. (OK.)
* Auto white balance. (OK - we can improve on that but it's fine for now.)
* Exposure compensation: none. (OK and the correct setting most of the time, but sometimes you have to change it. See below.)

What is happening in this particular picture is that you have two different areas:

(a) the tree and brown building.
(b) the surrounding street, bus stop, and sky.

Area (a) is mostly darkish in colour and in shadow. Area (b) is very bright. In other words, we have a classic example of a backlit scene, and backlighting is always challenging from an exposure point of view.

You can expose for (a) the darkish centre area, in which case cars and bus stop will be over-exposed and the sky will be blown out completely. Not great.

Or you can expose for (b) the sky, in which case the main centre subject area will be almost black. Not good either.

Or you can try to find some sort of compromise. Sometimes there is a good compromise, sometimes it is just not possible and you need to do something heroic such as (depending on the scene) using fill flash, optical filters, joining multiple exposures up in post-processing, or simply coming back at a different time of day. Basically, if things are a bit out you can usually tweak things and get away with it. (You are doing this with your manual post-processing corrections. The result isn't perfect but it's much improved.)

A second problem is that cameras' exposure systems don't know what they are looking at. They don't know if they are looking at the white sand of Bondi Beach or something inside a coal mine. So they guess. They simply assume that the scene is medium - not bright, not dark, somewhere in the middle. (Technically this is called "18% grey".) Cameras cannot "know" these things (though they are gradually getting better at guessing.) Only a human can reliably know what the picture is of, and which parts of it are the main subject and most need correct exposure.

In this case your camera is using a centre-weighted average for its exposure metering. It is deciding how much light to let onto the sensor (aperture, shutter speed and ISO settings) by taking an average reading, mostly paying attention to the centre of the frame but also considering the outer areas. All things considered, it's done a fairly good job. The first problem here is that the correct exposures for (a) and (b) are different. It can't do both at the same time! The second problem is that the central area (tree and building) consists of dark leaves and dark bricks. The camera doesn't know that these objects are actually quite dark and it has no way of knowing it. So it just assumes that they are medium and hopes for the best. Mostly that works fairly OK. But sometimes - as in your example - it doesn't.

You answer is to take control of the exposure yourself. Generally, this is done using a camera control called "exposure compensation". I expect that your phone will have that ability. (I don't use phones so I don't know how you do it. Other people here will know.) Note that you only need to take over and use exposure compensation when the scene is difficult (beach, coal mine, backlighting, etc.) and the camera guesses wrong. Most of the time they do a pretty good job.

Thanks for posting an interesting puzzle!

[RonB1949]

Thanks for your quick response. I'm generally pretty happy with the images my phone captures - I only use them for posting on Facebook and general home viewing. I can't afford a decent camera, and I like the ability to whip out the phone and capture something even if I haven't set out on a "photographic expedition"! The main problem is viewing the screen in sunlight, and keeping the phone from changing into other apps etc. I have "solved" both of these issues by making a box to put the phone in to shield it from sunlight and keep my fingers away from the screen!

Interesting that you recognised the shopping centre - do you live in the area?

I use the Camera2 API. I will experiment with alternative scene modes. What's sRGB? Is that the right setting?

If all else fails, I might just try batch adjusting the gamma when I upload the images to my PC.

Thanks again


Hmm...! DULLsville, alright, and I don't mean the Balgowlah shopping centre.
Your camera image shows a tonal flatness (your misitiness) and low saturation.

The processed version is only a minor improvement, and I don't mean that you
lack processing skills. I think you've got some challenging output from that
phone cam.

I take it then that these are out-of-phone jpegs, and...
...
I've looked up the picture-taking settings for the phone... - there aren't many.

Two things about Open Camera:
- it can't give you what your phone does not have;
- and anyway within this app you should select Settings-Camera API-Camera2 API
(the alternative is "original camera API", but that's used by the native camera app).

In whichever app you can access it, find Scene Modes and try a few that are NOT
"Normal" or "Standard".

Going back to one of your original questions about gamma settings, look for a Manual
mode setting. In the Open Camera app, press the square icon that contains the -/+
symbols. I don't know how in the native app.

And referring to one of Tannin's qs: the Exif in the posted photos DOES show sRGB
and Auto WB.

Finally, I've tried Irfanview to simulate your processing, and also Photoshop, and even
another freebie called Faststone Image Viewer. - A challenging image in all three.

- - - Updated - - -

Thanks for your extensive reply, Tannin. I think I covered most of the issues on my reply to ameer's post. As I said there, I might just have to accept that the images will always require "post processing". I appreciate that the camera has trouble working out what's the best point(s) to judge the exposure etc. I find it pretty amazing what can be done even with a simple, cheap app like IrfanView.

Thanks again

[Tannin]

Cheers Ron. Good to get a result.

SRGB is a colour space, essentially a way of mapping numbers (which is all a digital camera or a phone or a computer understands) to colours (which is all that we can see). There are many different colour spaces, nearly all of them designed for specific purposes. The standard colour space is sRGB. Nearly everything uses it. The only thing you really need to know about colour spaces is that sRGB is the one you want to be using and (almost always) the one you get unless you go fiddling with things. As background, there are reasons to use other colour spaces but use of them is technical and requires specialised knowledge, software and equipment. A good rule of thumb is that if you don't know anything about them, then you don't need to know anything about them except to stick with sRGB if the question ever comes up, which it mostly doesn't.

[ameerat42]

^ And it's "generally" the "right" one to use for most photographic applications.
(A bit of a sweeping statement and I'll get :violent10: for it, but there...)

No, but I went there some time ago for some reason...