I am working on a research paper concerning developing a CNN model for a multi-class classification on images. I have a large dataset consisting of 3 classes summing up to 20000 images. Class 1 has 7000 images, Class 2 has 10000 images and Class 3 has 3000 images. Can I subsample Class 1 and Class 2 down to 3000 images both, so I can have 3000 images for each class? I feel like oversampling can increase training time a lot.
Note: I have constraints on resources because I don't have a powerful machine. I only use the free version of Google Colab. I am willing to get the Colab Pro however I'm not from US or Canada.