In order to fill a given size paper with your image, you may have to crop!!!!
Cropping is not a sin nor against the laws of image editing.
You need to fill a 4×6 print completely with your image? Then it has to be a 2:3 ratio to begin with. The image file that you send to the printer has to match in proportions to the paper you intend to print IF you want it to fit to the edges either with a thin border or borderless with minimal expansion.
Regardless of what the ratio of my camera sensor was, I will always crop as needed to enhance the final impact of my image as much as it is possible. Then I will choose the nearest paper size I have on hand and print it with a border that further enhances and isolates it.
So for example, on my 13″ x 19″ final size paper print, the image me actually be 11- 1/4″ high by say 17 – 3/8″ in length. It does not have to be 12″ x 18″ or 11″ x 17″. It can be whatever the proportions happen to be after I cropped out ANYTHING that did not belong or enhance the final image.
The final image proportions are dictated by the artistic cropping you apply in order to provide the most visual impact in the end.
Please don’t get trapped in the “Camera Sensor must match your final image proportions ” argument.
Size and proportion your images for the BEST final impact and then simply fit them to a standard paper size with whatever borders will enhance them the best. Remember that IF you choose borderless, you will very likely have to crop either the sides or the tops and bottoms in order to make them fit standard paper dimensions.
No regular viewer in their right mind will ever ask you about whether you remained true to your camera’s sensor ratio. If the image was the initial merit and impact it should have, it does not matter if the proportions are not what is considered “Standard”!!
Joe AKA Jtoolman