I don't believe there is an official guide on all the methods to achieve a third person snapmatic picture, so figure I amass all the known methods together and forge a guide from them. Snapmatic is not limited to selfies so these methods allow you to further capture your character. You won't be capturing any complex pictures with these methods, but it's just nice to have the ability to take more than just selfies.
Method 1: The Vehicle method PATCHED
1. Park a vehicle or your personal vehicle anywhere
2. Get out of the vehicle and move far enough away with your online character, but close enough so when you press Y/Triangle, your character begins to walk towards the vehicle
3. As your character is walking towards the vehicle, open your phone and enter snapmatic
4. Take the picture whenever you please. You can also spin the camera around with the right stick as your character walks towards the vehicle, allowing you to set the angle
Method 2: The Drop Down method
1. Find a high enough surface to drop down from for this method. It has to be high enough where you'll have enough time to take the pic due to the duration of the fall, but not too high where your character will end up taking damage/wobbling down. I used this roof as an example
2. Stand near the edge. Try to get as close as possible to the edge without making your character automatically jump down.
3. Open up your phone and hover over snapmatic
4. As soon as you make your character walk forward to drop down, open snapmatic and take the picture when you please. If you wait too long though, snapmatic will reset itself into third person. This method can also be done while holding a weapon. Same for the vehicle method.
Method 3: The Melee Method PATCHED
1. Equip your fists, or any melee weapon.
2. Keep mashing the right trigger or R2 (assuming that's the attack/fire button on PS3) so your character will keep attacking with their melee weapon
3. As you mash the button, open up your phone and open snapmatic. As long as you keep mashing the attack button, it will keep cancelling out first-person snapmatic. Take the picture when you please. You can catch some good melee shots against pedestrains and such.
Method 4: The Grenade/Sticky Bomb/Tear Gas method
1. Simply equip one of the three weapons and hold LT/L2.
2. As your character is ready to throw it, open snapmatic and take a picture. Real simple. You can also take a pic after the weapon is thrown.
Method 5: Barbershop Method
1. Go to the barbershops with the female barber
2. On the right there will be a couch you can sit on by pressing right on the d-pad.
3. Sit down on the couch, open snapmatic, take picture
Method 6: Jumping Method (Hardest method)
This is no doubt the trickiest method but being able to take a 3rd person snapmatic pic almost anywhere makes it the most effective method.
1. Stand anywhere and open your phone, hovering over snapmatic
2. Jump with your character and as soon as you press the jump button, open snapmatic
3. Begin mashing A/X as soon as possible to take the picture and save it
What makes this method difficult is acquiring the angle you want, since sometimes when you jump, the camera automatically rotates so you have to try and adjust it as best you can mid-jump. It will take a few tries.
Method 7: Parachuting Method
While parachuting simply open snapmatic from your phone and snap the picture whenever you please. Just rotate the camera with the right stick.
Photo credit: Cmdr_Shepard
Method 8: Merryweather Rappel Method
1. Rappel from the Merryweather pickup chopper by holding down X/Square once you reach your destination. Rappelling is only possible if you are close enough to the ground or a roof.
2. You will have a very brief moment to open snapmatic and take a picture
Photo credit: Cmdr_Shepard
Bonus: Special Selfie
1. Open snapmatic and take selfie, but do not save the picture
2. Press Y/Triangle to delete the pic you just took, but right before you press delete, make your character turn 180 degrees by pressing down on the left stick
3. Take picture. You can capture your character with a few different possibilities of expressions