I've seen some low-light sample images taken with the Oppo F3 Plus' rear camera and I wasn't excited with what I've seen. Having a f/1.7 lens is great, but the lack of optical image stabilization forces sometimes forces the camera to shoot at very high ISO which results in very noisy images. There is one image here shot by Tech2 Photo Labs. It was shot in a very dark area. If you look at the EXIF, you can see that it was shot at ISO 3014 and with 1/14 sec shutter speed and without a flash.
You can see that most of the noise is visible in the dark tones of the images. This is a very challenging scene for any camera. The reason you can see the background is because of the f/1.7 lens and the very high ISO sensitivity used in that photo. If the Oppo F3 Plus had an optical image stabilization it could have captured a much better looking photo. By saying "better", I mean with better exposure and less image noise. An average OIS can provide around 2-3 stops advantage. Each stop allow twice more light to reach the sensor, and this is a huge benefit for low-light photography. You could have shot that same image with a shutter speed which is 2 stops less and still achieve the same sharpness.
This is a very extreme condition, but it demonstrates why an OIS is necessary when shooting in very dim lighting conditions.The reviewer who reviewed the Oppo F3 Plus for tech.firstpost.com website also mentioned that he wasn't pleased with the low light performance. A f/1.7 aperture can get to until a certain point and it's not like it's going to turn a night into day. The main problem is that the pixels on the sensor are very small. On a APS-C or Full Frame DSLR a f/1.7 is godsent. Not that I am complaining, the Oppo F3 Plus can still give you some really good shots, but an OIS would have made those images much better.