If you are shooting to resolve error 26 issues but fail to update your phone, there are some simple ways might help you out, such as use the latest version of iTunes, change another USB cable, turn off the third-party security software and so on. Possibly the DFU restore will fix it out but with data loss. Detailed introductions can be found here: Resolve issues of iTunes and third party software.
As I know, error 26 mostly causes by the bloated data partition and lack of storage space. This also means that it would be a little hard for you to fix this problem without data loss. But as described in how to get back photos from iPhone article, try to check out if you have created a backup in iTunes or iCloud. In this case that you are allowed to restore the latest backup to get this problem fixed. Or you can sign back to iCloud Photos Library to see if you can find your photos there.
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