Today’s Question: I was advised long ago that it is best to enlarge and then crop because the result is better than if you crop and then enlarge. What are your thoughts on this?
Tim’s Quick Answer: The order of cropping versus enlarging doesn’t make a significant difference in image quality, so I recommend using the approach that is most convenient in your workflow. That generally means cropping before resizing, because you would typically crop the master image and then only resize when preparing a derivative image for output.
More Detail: In general cropping involves simply removing pixels from the outer area of an image. In this context, whether you enlarge before or after cropping won’t make any difference in terms of image quality. I’ve heard arguments about there being a potential benefit to leaving the pixels in place until after resizing so that all pixels are available for the software that is calculating the pixel values for resizing. That is an incredibly marginal issue in my view, and would only affect pixel values at the very outer edge of the cropped image.
If you rotate as part of the crop then you are altering the pixels in that process. Enlarging before cropping and rotating would ensure that you’re enlarging based on unaltered pixels, but the reality is that you’re performing two alterations (enlarging and rotating) and there is no significant difference in the results from the standpoint of image quality.
Therefore, I don’t recommend making a point of performing the steps of enlarging and cropping in a particular order, other than based on what is most convenient for your workflow. In general, there’s no need (nor any reason) to resize the master image until you’re preparing a derivative copy of that image for output such as printing. That often means the image will have been cropped before it is resized for the final output, but it is perfectly fine to perform those steps in any order.