Lesson 3 - Official Topic

You will have one new version of it per epoch, each time you iterate through your data.

4 Likes

Why do we have both batch_tfms are also applied on images aren’t they

How is the RandomResizedCrop be applied to validation data?

A post was merged into an existing topic: Lesson 3 - Non-beginner discussion

Based on my understanding, in each epoch, the image will be cropped to a small area of the image and zoomed in. I may be wrong though.

1 Like

It’s a center crop.

1 Like

The min_scale takes 30% of the image at the time… is there an industry percentage that is recommended to use here?

How can we add diffferent augmentations for Train and Validation set?

4 Likes

My understanding is:

batch_tfms applies the SAME transform to all images in your batch.

item_tfms applies different transforms to all images in your batch.

See: Lesson 3 - Official Topic - #64 by sgugger

This is effectively what it’s doing. The model sees a lot more variations of the input images than if you didn’t have this randomized transform.

No, it takes a random percentage between 30% and 100% of the area (usually we use 0.35).

2 Likes

what is the different between mult=2 or 1 or 3 etc?

1 Like

Sorry for posting in the wrong forum, @sgugger!

The book states …

"On each epoch (which is one complete pass through all of our images in the dataset) we randomly select a different part of each image. "

But I thought the transformations were applied per batch … not per epoch.

1 Like

Think any of these transforms be better than padding (adding empty useless pixels).

That is incorrect, batch_tfms can apply a different transformation to each image. Rotation for instance, or flip, are random per image.

1 Like

A post was merged into an existing topic: Lesson 3 - Non-beginner discussion

On the validation set, we center crop the image if it’s ratio isn’t in the range (to the minmum or maximum value) then resize. Link is:
Documentation of RandomResizedCrop

2 Likes

At each epoch you get a new transformation.

Are there pre-packaged transformations that are not affine? Things like lightness, hue, sharpness…