You can choose to keep some photos private so you can complete challenges without subjecting your photo to public scrutiny.
The "OK" hand icon works like Instagram's "like" heart. Tap the camera to complete the same assignment as the image you are viewing.

A new app for iOS aims to motivate and inspire mobile photographers by merging assignment-based photography with a social media element. 

In many ways, OKDOTHIS reminds me of social media apps like Instagram or Flickr, but it also feels like a challenge-based photography forum with photographers trying to share their best stuff. Abandoning the hashtag system in favor or categories and "DO" assignments, OKDOTHIS is fun to browse as you see how users interpret the different assignments. 

Either take a photo inside the app or choose one from your Camera Roll.
Mix and match OKDOTHIS's four filters to create your own unique look.

Either take a photo or upload one from your photo library. OKDOTHIS has a few filters that you can layer on your image, but you'll likely opt to do your editing outside the app. Next, caption your photo and choose how you want to share it. 

Not only will OKDOTHIS give you assignments, it lets you create them as well. Pick from one of the 36 categories and create your "DO." Watch as your "DO" turns into a photo gallery of images from users around the world.

One of the coolest things about OKDOTHIS is that you don't have to use the social media element at all. You can choose not to publish to the photo feed and instead just save to your Camera Roll with the assignment name under the photo. This can be a great tool to motivate photographers without the added social media pressure. If you do choose to share on OKDOTHIS, be careful to make sure you set the "allow users to download" toggle to "off." Otherwise, your photo can be easily downloaded by anyone.

If you don't want people taking your photo, make sure the download toggle is set to "off."
Create your own "DO" challenges and see what fellow mobile photographers come up with.

Currently OKDOTHIS seems to be dominated by the selfie-obsessed teenage types, but the magic of OKDOTHIS is in its categorization system. You don't have to see the boring "my face when" photos if you aren't looking for them. Instead, you can browse some of the more challenging and interesting assignments.

The Pro Photographer and Street Photography categories are my favorites so far. Challenges in the Pro Photographer section include "Lighting test shot/self portrait" and "Tenebrism: Violent contrast of light and dark, where dark dominates the image." Street photographers are asked to document "The beauty of public transportation," "The magic light that bounces between skyscrapers," and an "Unknowing family portrait."

OKDOTHIS is only available for iOS devices running iOS 7 or later. It costs a steep $1.99 in the App Store, but that price hopefully means that it won't be launching Instagram-like ads any time soon.