MONSTER HUNTER: WORLD

You need to complete 20 photo requests from the lynian researcher for this achievement to pop. As far as I know, it can be any 20, including the requests which were added in later updates. Some of these are notably quicker and easier to obtain, such as the ones you can complete in Seliana.

You do not need to have gold grades for a request to be counted as completed. When the achievement popped for me, i had 3 silver grade photos. I dont know whether bronze grades count as completed or not, so to be on the safe side, try to get each request a silver grade before moving to the next one.

You can check your Observation log—located from your Hunter’s Notes, to see the exact requirements for each request and the conditions in which you can find the subjects.

A lot of this achievement is just traveling between areas in expeditions until you have the proper weather and time, and the photo op will usually show up as its own icon on the map for you to find.

There are five requests that can be completed in Seliana and the Seliana Gathering Hub that are very easy to get:
“Bath Connoisseurs”
“Say, ‘Sneeze!’”
“Gathering Hub Courier”
“The Quest Prepper Upper”
“Poogie’s Pursuit”

There are a few requests for pictures of certain monsters doing specific things(which you can always see the EXACT requirements and sighting info for in your Observation log), but most of the requests are for the unique grimalkyne groups in each area of the game. I believe you start off with one or two requests from each group available and as you complete the requests by submitting the pictures you will unlock more requests for that group. When you finish all the requests from one group of felynes (ex. Bugtrappers in the Ancient Forest), the Lynian Researcher will reward you with a decoration for your room, but keep in mind that you do not need to finish every request for each group, you just need to finish 20 total.

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A few tips for ones that i personally struggled with (these are ones where you need to recruit a grimalkyne as a tailraider and take them somewhere for specific conditions):
For “The Leaf Boat” in the Ancient Forest, with your palico you need to recruit a bugtrapper from their lair in area 17 and then travel to the water in area 9 and then you’ll be able to take a picture of your new grimalkyne pal on his leaf boat.

For “The Grimalkyne’s out of the bag” you again need to recruit a grimalkyne, this time a Protector, from their lair in area 8 of the Wildspire waste and then go back to camp with them, and take a picture when they are surprised by your palico rummaging through their things.

Lastly, for “Air Pollution” you must recruit a
Plunderer from their lair in area 15 of the Rotten Vale and take them to any area where the effluvium makes them cough. Areas 9 and 8 are good for this.

Keep in mind, like many achievements in this game, it can be time consuming and monotonous, but keep at it and you will get it! Good luck :-)