Hello and welcome to the forum!
I've struggled w/ iTunes and photo transfer from my computers and/or cameras since early 2011, so let me provide a few potential solutions although others likely exit. First, I really dislike using iTunes for 'photo transfer' and have stopped employing the app years ago for that purpose - but if you look at the first image below, one choice is to make one or several folders (the ones checked) and store the images you want to transfer to the iPad in those folders, so that only those pics will sync - there are issues w/ that method as you 'remove' images from your iPad and/or your computer's folders, thus not my choice any more.
Second, Apple's cloud and photo stream services have really developed in recent years, especially if you want to share your images across devices and w/ others - not a priority for me, so not a user, but an area to explore if the concept is of interest.
Next, there are a variety of photo transfer apps that can easily accomplish your goals using wireless technology - no cables and no clumsy dock photo connectors (had one for my old iPad 2, now sold, but did not buy a new one when I purchased an iPad Air 2 - do all wirelessly) - see the next 3 attached images - all of these apps are either on my device, computer, or both - google each to see if one or more may solve your photo issues. I also use Apple's
AirDrop a lot to get images and other files between my MBPro and my iPad.
Finally, concerning transfer of images from your cameras, I would forget about using a cabled attachment - my choice is to simply remove the SD card from my camera(s) and using either the built-in card reader or a USB card reader, transfer selected images from the storage card to my computer. There are a number of wireless devices that are inexpensive which use the SD cards and by establishing a personal Wi-Fi network (and using an appropriate app on your iDevice) transfer photos - the two that I own are shown below (the second one is more versatile as the description states). Dave
P.S. SD cards can be used in cameras that have built-in Wi-Fi (called Eye-Fi); in addition, I just purchased a new Lumix Panasonic DC w/ Wi-Fi and can easily transfer images from my camera's SD card (without removing it) to my iPad using an app from Panasonic - works like a charm.
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