iPads tend to come with rather limited storage (16BG to 64GB) and Apple places strict restrictions limiting the use of external storage devices such as USB sticks, SD cards and hard drives.
So what do you do if your iPad is full and you would like to bring a few films (ripped from legally-purchased DVDs) to watch during your holiday? Well, there is a way to do that without jailbreaking. It’s not without flaws and it only works with video files. But it works.
I described how to do this on a French forum a couple of years ago, and I recently noticed that my post got over 16,000 views! I thought it could be useful to translate it into English and post it here. Here we go.

How to externally store video files to view on your iPad
Firstly, you’ll need Apple’s iPad SD card adaptor. You can find it here or here, depending on whether your iPad has a 30-pin dock connector or the new Lightning connector.
Secondly, you need an SD card to store your films. These come in all sorts of sizes nowadays (up to 128GB). To give you an idea, a full-length film will weigh between 1 and 2GB, depending on your preferred quality. Your SD card must be formatted using the FAT-32 file system. You can do this in just a minute on a Mac or PC, just Google it if you’ve never done it before.
Thirdly, the video files: The films you want to watch must be encoded using the h.264 video codec for which iPad has hardware support. Audio is best supported in AAC format. File format can be either .m4v or .mov. To rip a DVD into an iPad-compatible video file (using one of the above formats), I recommend that you use (and make a small donation to) the excellent Handbrake. It has an ‘iPad’ preset which will do the work for you if you don’t want to hear about codecs and file extensions.
Next, you need to place the videos on the SD card. Simply copying the files onto the card will not work. As you are using the Camera Connection Kit, you need to make your iPad believe that you’re trying to unload videos you’ve shot with your own camera. For this, create a folder called ‘DCIM‘ on your SD card. Inside this folder, create another one called ‘102_PANA‘ (that second folder can have many names, but I have tried and tested this particular one).
Then you’ll need to name your videos like they’ve been generated by a camera. Many names will work, but I recommend the following: start with ‘P1000769.m4v‘, then increase the number by 1 for each new file: P1000770, P1000771, etc. These imitate the file names generated by a Panasonic camera and will be recognised by your iPad.
Once this is done, open the ‘Photos’ app on your iPad (NB: even though you want to access video files) and plug in the adaptor containing your SD card. A new tab, “Camera”, should appear. Tap this tab and your videos should show.

To watch one of the videos, tap on it and choose “import selected”. This will download it onto your iPad. This means that you must save enough space on your iPad to accommodate the largest of your files. Once viewed, the file can be deleted from the tablet.
Drawbacks
The main drawback of this method, as you may have seen on the above screenshot, is that file names are not displayed when iPad accesses the SD card. The only available information is the length of the file. This is not a problem when you have 2 or 3 films on your SD card. You can download one and check if it the one you want.
However, it becomes tricky when you store a number of episodes from a TV series, which are all about the same length. I do not have a solution for that problem. A workaround can be to preemptively make a note of the length of every episode, in order, and use some additional notes to distinguish those of similar lengths. It’s far from ideal, but if you’re like me and you really cannot go on holiday without taking with you the whole of Arrested Development, it’s a good enough solution.
Another drawback is that, predictably, DRM contents (i.e. films purchased on iTunes) are not supported by this method.
Anyway, I hope this can be useful to some of you. Any comments or questions welcome.