Even as the debate surrounding the HTC One M9's camera rages on, there's no denying HTC has one of the most feature-filled camera apps of any high-end smartphone. There's a huge number of different modes to use and settings to tweak — from the usual options like HDR and panorama to recent additions like the new RAW camera, which lets you to take your smartphone photography the next level. We'll take a look at everything the HTC camera app has to offer after the break.

Switching between cameras There are a couple of easy ways to switch between the HTC One M9's main camera modes. Hit the modes button (four circles) in the bottom left corner to see an overview of all your camera features. The five main ones will appear here, along with any additional modes you've added, or custom cameras you've created. Verizon is offering the Pixel 4a for just $10/mo on new Unlimited lines

You can also jump between different camera modes by quickly swiping left or right in portrait mode, or up or down in landscape mode.

The main camera mode If you just want to focus on taking photos quickly without fiddling around with settings, the HTC One M9's automatic shooting mode is where you'll live most of the time. Simply select "camera" from the modes menu to make sure you're in this shooting mode. By default you'll just see a relatively simple UI — flash controls in the top right corner, a preview of your last photo in the top left, still and video shutters in the middle, atop the modes menu. If you don't want to worry about tweaking settings and changing modes, this is probably all you'll need to take decent photos on the M9. But if you want more control, HTC's camera app can provide it. Tap the menu button (three dots) in the corner of the screen to bring up the menu bar. The six icons that appear each give you control over a particular aspect of the M9's camera.

The still shot menu lets you choose between presets for still pictures in different environments. There's a night shooting mode designed to assist with low-light captures, an HDR mode that'll balance exposure in shots with very bright and darker areas, and presets for portrait, landscape and macro (close-up) shots as well. Seasoned photographers will also want to play around with the HTC camera app's manual mode (M), which gives complete control over white balance, ISO , shutter speed and focal point. We've gone into greater detail on taking great shots in manual mode in our HTC One M9 photography guide.

The video menu gives you a couple of extra video options, in addition to shooting plain old video at the normal 30 frames per second. Slow motion mode, as the name suggests, takes slow-mo video, though at a lower resolution of 720p. Fast Full HD records at full 1080p, through at double the frame rate as standard video, making your video appear smoother.

Max ISO lets you control the maximum sensitivity value of the camera, balancing between image brightness and noise. A higher ISO value will give you a brighter, though noisier image, meaning the M9's software will need to do more post-processing to remove that noise — the result might be a brighter, less clear image. By contrast a lower ISO level would give you less noise, but a darker overall image.

EV stands for exposure value, and as you'd expect, adjusting it up or down gives you a brighter or darker image.

The white balance control gives you a few presets for tweaking your photos so colors don't look too yellow or blue in certain lighting conditions. To let the camera itself decide, choose AWB (auto white balance)

Camera settings From the camera menu, press the cog icon to open the camera settings menu. Here's where you can save a custom camera with all the options you currently have configured, as well as fine-tune all the other camera features that aren't in the main menu bar. Here's a run-down of some of the main settings you'll need to know about. Crop controls the aspect ratio of photos you take — basically, the proportions of the rectangle you're shooting. The default value is widescreen (16:9), which takes photos that match the proportions of the M9's display. The camera's sensor, however, comes in at 10:7, so if you want to take advantage of the full 20 megapixels, this is the option for you.

Make-up level is self-explanatory — use this slider to control how much automatic smoothing is applied to faces in your photos.

Same deal with Continuous shooting — this lets you hold down the shutter key to take a burst of shots. You can choose to limit it to 20 frames, and automatically review your burst capture once you're done.

Review duration lets you choose to view your photo on-screen for a few seconds after taking it, with a few options available to determine just how long your preview is shown.

Self-timer and resolution are also pretty simple — the former lets you set a timer for your photos, just as you might on a full-sized camera. The second controls the physical size of the photos you take. Generally you'll want to choose the highest available to capture the most detail, though if you're more concerned with file size and saving storage space you might opt for "medium" instead.

Similarly, video quality determines the resolution of your video footage. The M9 can record at up to 4K resolution, but only for up to six minutes at a time. Most of the time you'll want to stick to the standard 1080p (Full HD), which has no such restriction, or 720p (HD) if you want to save space.

Image adjustments let you tweak the contrast, sharpness and saturation of your photos up or down, if you're not happy with the default values. As we discussed in our M9 photography guide, we've gotten good results by tweaking the sharpness down a little, and nudging the saturation up.

General Settings houses even more toggles. You can have the camera app overlay a rule-of-thirds grid to help with framing your shots, geotag photos so they save details of when and where they were taken, and switch the shutter sound on or off. You can also control whether the volume button acts as normal, captures a photo or zooms in and out when taking pics.

Bokeh mode Last year's HTC One M8 included a depth-sensing Duo camera to create defocused background effects. This time around HTC achieves this effect with a single camera and software trickery — Bokeh mode is designed to produce artistically defocused backgrounds behind your subject, and it works best in shots with a clearly distinguishable foreground and background.

The effect works pretty well, but it's not infallible — you can notice areas where the foreground isn't quite blurred properly, or areas of the subject are blurred when they shouldn't be. But as it turns out, the HTC One M9 as a pretty good dedicated macro mode as well, which achieves the same effect using good old-fashioned light and glass for close-up pics. Bokeh mode is can be fun to play around with, but be aware that your mileage may vary.

Selfie mode Everyone loves selfies. Everyone. And the M9 includes a dedicated mode for taking pictures of your mug using the front-facing Ultrapixel camera. Some of the options from the regular camera mode are available, but those given prominence are the self-timer toggle (choose from off, 2, 5 or 10 seconds) and the make-up slider. Positioned along the left side of the screen, this aims to smooth out your skin and mask any imperfections, with the two extremes ranging from what you actually look like, to what an animatronic waxwork of you might look like.

The M9's front camera uses the same Ultrapixel technology we've seen from HTC in rear cameras over the past couple of years. That means it's better suited to darker conditions where you're more likely to be taking selfies than the 20-megapixel rear shooter.

RAW camera The latest version of the HTC camera app introduces RAW camera mode, which is essentially a significantly expanded version of the manual shooting mode in the regular shooting mode. You'll get sliders for white balance, EV, ISO, shutter speed and focus, and you can tweak these to your hearts content. In addition to taking a plain old JPEG though, the RAW camera captures a DNG (digital negative) format RAW image. This captures more information than what you'll see in a JPEG, allowing photography enthusiasts to process them in professional software.

Shooting in RAW and then processing later in apps like Adobe Photoshop or Lightroom allows you to fine-tune every aspect of your photos. The main trade-off is file size — RAW images from the M9 can weigh in at around 40MB apiece — and capture speeds — naturally you're capturing a lot more data, so doing so will take a little longer. Getting DNG files from your phone to your computer also isn't as easy as you might hope. The simplest way is to plug in and find them like you would a normal digital camera. Alternatively the built-in HTC File Manager app can be used to track down DNGs and share them with your cloud storage app of choice. MORE: Android and RAW images - Everything you need to know

Panorama Panorama modes on HTC phones have been hit and miss in the past, but the M9's is actually pretty decent. It's made up of two main shooting modes. Sweep panorama produces a regular left-to-right (or right-to-left) super-wide photo, and due to the dimensions of the M9's sensor these are best captured with the phone held in portrait orientation. Smooth, steady motion with as little vertical shift as possible is key to getting the best-looking panoramas possible out of your M9.