As you can see it's pretty big. Not something you want to put in a slider but rather in cams/cam phones. I hardly think the cam should be important for this device, or the light.

And it sucks. Just like LED flash. Flash can't solve sensor limitation in low light.

True. And the amount of pixels is only a half (if not less) of the truth. One should be more worried about the quality, not quantity of the pixels or the colour of a led flash.

Noise is solely based on sensorsize, amount of MP doesn't matter. More megapixel can* be even less noise when viewing on the same resolution / printsize. This is because more pixel can average noise out better.

Only way to improve imagequality is to gather more detail AND available light. Available light can be fixed with flashes. Xenon can deliver way more light than LEDs.

* The optics has to be able to deliver the amount of MP, if the optics doesn't there's no way then the noise can't be averaged out as much.

For Xenon flash, it is achievable. But it needs way stronger power supply than LED, so we must re-design the PCB to some point.

The question is if it is worth the time and effort, and if the majority happy to wait and pay more.

Our main difference is having a slider keyboard inside the device, because of that our work and device complexity is much much more than a normal phone. We need to position the sliding frame correctly, need to have quite some additional FPCs, need to implement additional sensors for keyboard, need back lit, need to control thickness etc. All those efforts are not easy to achieve, and will make the device expensive. (And again we are a small team, we don't have so much resources on engineering and we are doing something big companies don't bother to do because of complexity.)

So in theory adding Xenon flash it is possible. But we are based on a slider phone it's not the same amount of work as a normal phone. It's all come into the same question about timeine/money in the end.

PS: LED can be used as torch but Xenon can't.

I use my Nokia 808 often. It has an LED along the Xenon flash for use as torch and for finding the focus.

The Xenon flash is awesome, no doubt. Its way brighter than an LED and thus the phone takes way better pictures in the dark in distances of 3-4 Meters and below.

But it also has a little downside beside the size: It will take a little to reload. Half of the space it uses in the 808 is a giant capacitor. You can make fast image series in the dark.

Besides that: You rarely want to use it. The flash changes colors slightly and I only really enjoyed its benefits when taking pictures at night at a beach or when I took pictures of an unlighted chapel without windows and old paintings.
If I have the chance, I just take out my tripod and take pictures in natural lighting.

So: Its awesome in the rare situations you need it, but I don't miss it most of the time. If this would be a camera phone a Xenon flash would be a feature to be demanded. So its just too much hassle for the result.

Much more important are: a big enough aperture and the possibility for long exposure times.

I have two professional cameras and have had others in other brands before, none of them have built-in flash (and in fact I don't think any semi-pro or pro camera have built-in flashes). There is one main reason for dropping the flash: if you want extra light to expose your pictures, you have to do it properly, i.e., not with the limitations that come with built-in flashes, so you'd better off dropping the features that won't be up to that standard and still come at a cost.

Of course phone cameras are not the same, nor do they serve the same purpose, and it's arguable that a flash could be more useful on a phone since the main purpose of the camera is to take souvenir shots rather than artistic pictures. Plus their sensors do not show the same performance in noise control. I acknowledge that. But if we come by that definition, there's little support for justifying the bulk of a xenon flash and design/power supply issues it brings, a LED flash should be plenty enough for taking a souvenir picture, and even the best (!= powerful) flash won't do miracles when placed 5 mm next to the lens right in front of the subject.

I see. So its not worth the hassle then.

@Kaboulik

My a6000 has a built in flash, which does a fine job as a fill-flash.

Another point where the Xenon flash rocks is to take picture of things in motion (like kids). The Xenon flash duration is a lot shorter than with LED, so that the scene is frozen on the pictures, and not blurry like with LED.
I was once surprised while looking at a picture of a circular saw running at full speed, that on the picture the blade looked still. It may not be the effect you have wanted, but it allows to froze a picture to that point.

Despite loving it on my N8, I am not sure it is worth the trouble to add it to this phone.

Some other thinks that could help with phone cameras quality in low light are, among others : sensor size, optics quality, and technologies like OIS (Optical Image Stabilization).
OIS would not help when taking pictures of things in motion, but would help when taking pictures in low light with long exposures. It would also help with videos. Not sure how the cost of such techno is, and the difficulty to embed one, but it exists...

I agree that a flash can still be very nice in case of motion or filling (although filling would work with LED as well, just to a lesser extent), at least when you need it even it it's not necessarily common. It's a nice comfort on a phone to take all kinds of pictures with the camera you always have in your pocket. But as Macros and Chen said, the main goal of this phone is to be a keyboard phone and not a camera phone, and these two things are hard to reconcile in the same design (and I have a clear preference since I don't really care about camera phones, but that's personal taste and the market shows that most people think the opposite ). A LED flash seems like a nice compromise.