ios 8 / iphone 5s - deleted photos, memory still appears occupied

To make more storage space on my iphone, I went through and deleted about 1,300 photos from my iphone. They were in my "recently deleted" album for 30 days and then they disappeared. So I expected to have more storage available on my iphone (maybe 10 GB more?).

But no, something is wrong. Whenever I attach my phone to the laptop by USB, it still appears that I have thousands and many GBs of photos.

I have a 32 GB iphone 5s, and I have installed ios 8.1.2. I back up my iphone to my laptop only. I do not use iCloud or Photostream. My laptop is running Windows 7.

I can't see the deleted photos anymore on my phone. But I think they are still occupying the memory. I received a warning that I was running out of storage.

To try to fix this, I did a back-up and then restored the phone tonight. Three hours later, I have a little more storage available from removing "other" files. But the photos still look like they occupy many GBs.

I'm at a loss. Has anyone else experienced this? Did your phones end up overwriting deleted photos when you needed more storage? Or is there a fix?