Hopefully, if you are reading this you already know that number of megapixels is not the determining factor when it comes to camera quality
(if that was the case Chinese phones for 100€ with 24 megapixels would easily outperform iPhones with their measly 16 megapixels - but they don't.
For a longer explanation check out this post: https://steemit.com/technology/@hwtrendsetter/who-do-smartphones-for-50eur-have-more-megapixels-than-those-for-500eur )
But you might have also heard that ever since those new 48 (and ten 64) megapixels sensors were introduced, they restarted the megapixel war. And since they all new, there aren't any unbranded useless 48/64 mpx sensors. So as long as the phone has that many megapixels - it's at least decent.
This used to be the case back in 2019 when those sensors were first introduced, but unfortunately, this is no longer true. Some phones take terrible pictures despite having 48 or 64 megapixels.
As of now (2nd quarter of 2021) only 108 megapixel Samsung S5KHM2 sensor is "new enough". In other words, you can be sure that the camera is 'decent enough' when it's 108 mpx.
So one possible shortcut is to get the cheapest phone with 108 megapixels and call it a day. Unfortunately, they tend to be rather expensive.
One way to look at camera performance is to follow professional rankings such as Dxomark. However they are sometimes biased and since photography is a form of art, personal preference is also important. For best results, I strongly recommend comparing photos between devices directly. There are plenty of videos on Youtube, and Notebookcheck.net reviews also provide at least a few photos for comparison.
However, to compare photos directly we need to make a list of all models that we think may potentially be good choices within the budget. And then narrow down our list to just a few models.
Is there a way to do that? Absolutely - there are even a few tricks.
Firstly rule out phones with no Electronic Image Stabilization (EIS). If you plan on taking photos with a tripod you are probably a professional photographer and you shouldn't bother with cheap mid-range phones and get a DSLR camera instead. And if you plan on taking photos with your hand, stabilization is the key - especially when lighting conditions aren't perfect.
The second trick is to rule out phones that can't record at least in 4K 30 FPS. Not because this format is usable (quite the opposite - you should probably record in 1080p 60 FPS when possible) but it does usually reflect how much information can be absorbed and processed by the phone camera. If the sensor is too small or too slow, it won't' be able to record 4K footage. And you don't want a camera with a small and slow sensor.
You can also a look at reviews of phones that were released recently and quickly glimpse if they say that camera offers good value for money. If they state that it performs below expectations for this price point - remove it from your list. Remember that this only works for phones that were released recently and are priced about as much as on the release date. If a phone was released a year ago for 500€ and camera performance wasn't spectacular for that price range, if it now costs 200€ it may offer a very good value for money.
After narrowing down your list to 4-5 models it's time to check the reviews photo comparisons on Youtube.
If you still can't decide - ask yourself if the quality of the photos on the remaining phones (doesn't matter if 2 or 5 phones are remaining on the list) is acceptable for you.
If yes - check the remaining parameters - perhaps you could use a bigger battery or higher capacity storage.
Or just get the cheapest one ;)
Or if you really can't be bothered - check out this article https://steemit.com/hardware/@hwtrendsetter/acceptable-camera-phones-for-169eur-or-less