Because while it seems to work fine, I prefer to not have images from various shoots all on the same card without uploading. If the card fails, then all I've lost is the images from one shoot. I can usually reshoot it. If I have multiple cameras and multiple shoots on the same card and it fails then I've got issues that are difficult to fix.
So, best practice is format, shoot, upload, backup, format. OR format, Shoot, backup, format.
And yes, generally I format when I complete an upload and format again prior to the shoot. It helps verify that the card in the camera is good and ready to go.

If you noticed,the post you replied to was prefaced with LOL. While I don't intend to do that,it would be possible. As far as your doubts about my flitting back and forth between geographical areas,you are totally off base. Yellowstone Park geology and geography vary significantly and different days and times in the same area are quite common,so yes, I do flit. Different times and dates in Florida sanctuaries are another example. You also make the assumption that I rely upon software for sorting and that having back-ups on cards by area might not be desirable.

My original post was fairly explicit. My apologies for being thin skinned,but in addition to the non-answers received here,you should see some of the arrogant and condescending PM's I have received for my question. (Along with some good ones.) Most people simply do not follow a thread and just inject whatever strikes them.

Ah, but initially your question was about using the cards in different cameras, not about different days and times.
As using software to sort, how else would you? You are using SD cards, so they are digital images.
Unless you have all your photos printed and then sort, you are using software to sort them. How else would you?
Never mind back-ups on cards by area, back-ups on cards is not desirable unless very temporary: cards are small, get lost too easily.
Finally, when I reply to a message, I hope it will be useful to the OP, and I know sometimes it is not.
But we are not writing these messages in a vacuum: There are almost 73,000 users subscribed to this section, I would like to think that a few more than OP could make use of what I post.

That is a viable method and certainly will not cause you any problems.

The fact is that the format required for all of the OP's cameras is exactly the same. Off hand I am unaware of any DSLR made in the last several years that uses a different format. Hence a card formatted in any one of his cameras will function perfectly in all of the others. Any card with more than 2 Gb of capacity must be formatted as FAT32 or exFAT.


There is a difference between what each of those cameras do, but it is not formatting.

Any of those cameras will immediately look for the unique directory structure used by that camera. The structure of the directory tree is specified by a JEITA Specification. Hence all cameras will first look for a top level directory named "/DCIM/", and if not found it will be created. (Though not part of formatting a card, when a card is formatted that is what happens in the next instant. Hence a card formatted in a PC or a different camera will work the same as one formatted in the specific camera.) Once that directory is found the camera will look for, and create if it is not found, the camera's internally determined current default directory for writing images. The format for this set of subdirectories starts with a three digit serial number with a range from 100 to 999, followed by an up to 5 character identifier. A Nikon D810 might start with 100ND810 as an example, and would thus avoid conflict with any other model from any manufacturer.

Each directory can hold up to 9,999 distinct image file names.

In fact the DCIM Standard works extremely well. I've used multiple cards in multiple cameras for years with never a hint of trouble, and many others here on UHH and elsewhere have said the same thing.

Realizing what can be safely done is sometimes useful.