I have converted the convolution layer from 3 channels to 4 channels. Is it means the first layer is also re-trained using target images?
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model = models.resnet18(pretrained=True)
model.conv1 = nn.Conv2d(4, 64, kernel_size=7, stride=2, padding=3, bias=False)
num_ftrs = model.fc.in_features
model.fc = nn.Linear(num_ftrs, num_classes)