Posted by: Sclera

One reason why it's so difficult to get true before-and-after progress photos:

 

Original reddit thread: https://www.reddit.com/r/gifs/comments/4uqe7v/they_say_the_camera_adds_10_lbs/

Rebrn thread that unpacks the comments: http://rebrn.com/re/they-say-the-camera-adds-lbs-2717530/

This is why the main rule is to take photos from far away - if you're using your smart phone, then your physical placement is affecting the depth of field. The farther away you are, the more accurate the image is to what the human eye sees.

 

I remember someone having told me that, depending on the camera, your face may get "deformed" search for - stephen eastwood lens distortion ,

stephen eastwood and a famous model photographer who proved this   -  http://stepheneastwood.com/tutorials/lensdistortion/index.htm

Maybe you understand better by researching since English is not my native language and I do not know how to express myself so well using google translator I hope this helps

This is why I learned never to use selfies on a cell phone camera for online dating.

@banknote -- Yes, this is the exact same concept!

This is called perspective, depth of field refers to the distance between the first and furthest point in focus.

With perspective the further you stand from the object you are shooting the less distance appears between its closest and furthest elements. The furthest and closest elements are said to be "compressed". With people this results in the nose appearing less prominent compared to the cheeks and will make the person look wider than how you perceive them in person.

On a 35mm camera the most close to real life perspective can be achieved with 75mm, but the same result can be achieved with any lens or camera as the effect is a product of distance. The lens only provides cropping of the scene according to its length. You can try this with your mobile by stepping back as if you were framing the subject with a long lens and shooting then cropping the picture to the desired frame. The perspective will be the same but the draw back is that you will lose resolution and with a phone camera picture get a pixlated final picture. 

Thank you for the correction, @abdul-2!