Confused over Photo Storage?

[Beards]

My question is to do with the two different results for photos and videos on both the device Storage and on iCloud?

Under Settings/General/Storage & iCloud Usage:- the Storage/Manage Storage informs me in my Photo Library I have used 20.4GB and under my Photo Stream 2.1MB.

Under the same but for iCloud the Manage Storage informs me I have 19.3GB of Photos and Videos.

My question being:- Whilst I understand my iCloud storage and that all the photos, videos, albums etc are shown on all my devices my confusion lays with the Storage of Photos and Videos on the device.

i.e. On the device storages of my two main devices my Phone says I have used 20.4GB but on my iPad Pro it says 18.3GB. Obviously both devices reflect the exact same for iCloud Photo storage.
If these two devices show different results for photo storage where exactly are they stored and why is there a difference in size between the device storage and iCloud storage?

Hoping someone can shed some info, thanks.

 

[Beards]

Anyone have an input please.
I honestly thought by saving my photos to iCloud the photo storage on the device would be negligible but here I am with 20.4GB used space for photos on the phone. It's all a bit confusing.

 

[archer75]

I don't use icloud but Google photos has an option to delete all photos on the phone that have been backed up.

 

[aristobrat]

When you have iCloud Photo Library enabled, it will free up space on the devices by replacing the full-resolution copy of photos with lower-resolution copies. If you ever go to look at a photo that is low-res, it'll download the full-resolution copy on the fly.

So the amount of storage used for photos on different devices can vary with that.

 

[glhaynes]

When you have iCloud Photo Library enabled, it will free up space on the devices by replacing the full-resolution copy of photos with lower-resolution copies. If you ever go to look at a photo that is low-res, it'll download the full-resolution copy on the fly.

So the amount of storage used for photos on different devices can vary with that.

Note that it'll only do this if you turn on "Optimize iPhone Storage" (as opposed to "Download and Keep Originals").

 

[Beards]

This is part of my issue: I have "Optimize" set so only a low res/thumbnail should be on my devices.
However, when I look at the actual storage on the device it tells me I have used 20.4GB in my Photo Library yet the iCloud photo storage is smaller at 19.3GB.
Surely the iCloud Photo Library should be much much larger than the devices Photo Library if "Optimize" is set?

 

[aristobrat]

I'd looking in Settings > iCloud > Photos and see if it shows anything waiting to be uploaded...

 

[Beards]

Thanks but no, everything is uploaded. This has me totally stumped.