Do fingerprint smudges on a phone's camera affect the quality of your pictures? Short answer: yes. Long answer: not always, at least not in ways you'd notice. But you should still keep your phone and camera clean.
An iPhone, Pixel, Galaxy and Moto walk into a photo test
I conducted a very unscientific test using four phones: , , and . I took two pictures with each phone: one with a clean lens and the second with a single fingerprint on the lens (I just tapped the lens with my finger). I chose different subjects intentionally because this wasn't a test comparing phones against each other.
The dirty lens photo from the iPhone 7 was quite hazy and blurry. The dirty lens pictures from the Galaxy S8 Plus and the Pixel XL seemed to show little if any loss to image quality. Several co-workers had a hard time figuring out which of the Pixel XL's two photos had the fingerprint.
Then, there was the Moto G5 Plus. The fingerprint made it hard for the camera to find a focus point and added a slight haze to the picture.
Checkout the gallery below to see the actual photos from the test.
Getting between you and your picture
Smudges create a thin layer of grease on your camera which can easily cause distortions. But the condition of my phone had some effect, too.
The iPhone 7 I tested had been used heavily for 7 months as a daily driver and without a case. It's in great shape visually, but my guess is that the chemical coating on the lens cover has worn down a bit. The coating on the display has worn down, too and almost always has fingerprint smudges on it.
I did this same test with a colleague's iPhone 7, which had been used much less, and the results were less drastic. The "dirty" photo had only a thin hazy blur instead of the more pronounced one from my phone.
By comparison the Samsung Galaxy S8 Plus I had was only a few weeks old and the Google Pixel XL has basically lived inside a Google Daydream VR headset since I got it. The coatings on both phones seemed close to new with little if any fingerprint smudge build up occurring.
Infinity fingerprint smudges
When the Samsung Galaxy S8 first came out, many. Not only is the sensor on the back of the phone, it's right next to the camera which could lead to many accidental touches of the lens with your finger.
Samsung ingeniously has a notification that pops up from time to time on the S8 to remind you that "a clean lens makes for a better shot. Clean your camera lens to keep taking great pictures."
But, in our very anecdotal tests, the Galaxy S8 suffered little if any reduction in image quality from a stray fingerprint on its camera lens. While this doesn't solve the ergonomics of the S8's hind-side, you won't have to worry too much about those accidental camera touches unless the lens coating has worn down.
Your phone can never be too clean. Seriously, take a moment and envision all the places and things your phone comes in contact with. Yeah, pretty disgusting, right? This not only affects your camera, but you may have a literal hygiene nightmare on your hands. Seriously, your phone should not look like an episode of CSI: Crime Scene Investigation.
So what's the best way to clean your phone and its camera? A wipe on your pants leg? No that will just smear things around more.
Both Apple and Samsung recommend using a clean lint-free cloth (like microfiber) to clean your phone without any cleaning products -- window spray for example. If the build up on your phone is pretty heavy, use a mixture of distilled water and rubbing alcohol or vinegar on the cloth to clean the phone. Warning: vinegar smells like vinegar and so will your phone. We have a simple cheap cleaning solution recipe here at CNET.
If your phone is in a case, definitely take it out to clean it. Beware when you open that case it might look like an archaeological cross sample of your day-to-day life from the past year. Clean both your phone and the case before putting everything back together.
Once your phone is clean, keep a clean microfiber cloth with you to quickly wipe away any fingerprints or smudges, especially on the camera.
Common sense would tell you that if you get fingerprints on your phone's camera lens then your pictures will look bad. And while that is true, the extent of its badness is dependent mostly on how worn your lens' coating is and the amount of fingerprint build-up on the lens.
The good news is that your photos won't be all that blurry even if you touch the camera lens. But despite this, you should still clean your phone and its camera regularly to battle against germs, general yuckiness and anything that will compromise the look of your photos.