How do you put 0.5 on your camera

A few iPhone models have a 0.5x zoom, but it may not be available in all situations. Here are a few reasons why you might not be able to use it:

1. The 0.5x zoom is only available in the iOS Camera app. If you are trying to use it in another app, such as Messages or Mail, it will not work. On iPhone models with Dual and Triple camera systems, toggle between 0.5x, 1x, 2x, 2.5x, and 3x to quickly zoom in or out (depending on your model). For a more precise zoom, touch and hold the zoom controls, then drag the slider right or left.
2. You are in Portrait mode. The 0.5x zoom is not available in Portrait mode. If you want to use the 0.5x zoom, you will need to switch to Photo mode.
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3. You are using a third-party camera app. Some third-party camera apps do not support the 0.5x zoom. If you are using one of these apps, you will need to use the Camera app to use the 0.5x zoom.
4. There is a problem with your iPhone's camera. If you have tried all of the above and you are still unable to use the 0.5x zoom, there may be a problem with your iPhone's camera. In this case, you will need to contact Apple support for help.
5. Change your Photographic Style: Want to change the Photographic Style that you set? Just open the Camera app, tap the arrow , and tap Photographic Styles . Standard is the default, balanced style that's true to life and can't be customized, but you can swipe left to view other preset styles that are customizable. Tap Customize  to adjust the Tone and Warmth of the style that you've chosen.
6. Do you see this on your iPhone --> About genuine iPhone cameras
7. Sometimes, a simple restart can resolve temporary software glitches. Turn off your iPhone, wait for a few seconds, and then turn it back on.
   1. Restart the device. That's it.
   2. Still not solved --> Force restart iPhone - Apple Support
8. If the issue persists, you can try resetting all settings on your iPhone. This will not erase your data but will reset all personalized settings to their default values. Go to Settings > General > Transfer & Reset > Reset > Reset All Settings and confirm the action. Note that you will need to reconfigure your settings afterward. All settings—including network settings, the keyboard dictionary, the Home screen layout, location settings, privacy settings, and Apple Pay cards—are removed or reset to their defaults. No data or media are deleted.
   1. Reset All Settings: Return iPhone settings to their defaults - Apple Support:- Return iPhone settings to their defaults
   2. You can return settings to their defaults without erasing your content.
   3. If you want to save your settings, back up your iPhone before returning them to their defaults. For example, if you’re trying to solve a problem but returning settings to their defaults doesn’t help, you might want to restore your previous settings from a backup.
9. Make sure you have the latest updates installed.
   1. Update Over-the-Air (OTA) —> Update your iPhone or iPad - Apple Support (IN)
   2. Update using iTunes/Finder —> Update your iPhone, iPad, or iPod touch - Apple Support (IN)

If none of the above steps resolve the issue, it is recommended to reach out to Apple Support or visit an authorized service center for further assistance. They can provide specific guidance based on your device model and iOS version.

You may get better and prompt responses if you may kindly provide the iPhone Model that you have and the iOS version if it is known to you and re-post.

With the limited information that you have provided, It is hard to even guess the problems faced by you. 

You may get faster and better responses to your query by --> Writing an effective Apple Support Commun… - Apple ...

Please re-post with detail so that someone else can help.