I have trained my classifier on pictures with a mixture of several classes on each picture, e.g. A-F. The classifier is able to (nearly) correctly segment those classes on the images.

Now I got more data with pictures showing class G. To minimize my work, I only labeled class G on the images and left the rest out (Invalid).

Two questions for my training arise:

  1. If there are no examples of class G in my first dataset (because it could have been a subclass of A-F), how do I train it correctly? Suggested Solution: I can add my new data to the old one, but I have to tell the CNN when there is an image with class G, because I have to change the error measurement of my CNN somehow. But how?
  2. If G was included in my first dataset (assume G is 'police car' and B is 'car', but some images showed police car), how do I train in this case correctly?

Transfer learning is what you want to need.

Checkout this note from CS231n, it provides some general advices on transfer learning and model fine-tuning.

In the meanwhile, this blog from keras shows how to use pre-trained VGG16 network to classify dogs&cats.

  • $\begingroup$ I know that I have to finetune - but I am interested in how to adapt the new classes. Any more specific answers on how to model it exactly? $\endgroup$ – N8_Coder Feb 20 '17 at 6:27
  • $\begingroup$ Does this gist help? $\endgroup$ – Icyblade Feb 21 '17 at 6:23

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