Thanks to KarenJ for her answer,

Regular gallery is 4000x4000, Writers is 450x450

Are the text limits also provided (spelled out) in the same manner? 

BTW, I don't know where to find the limits (both file size and text size) for messages posted in the forums ... could you elaborate? 

Could you suggest that information appear in the forum message upload page(s)? 

Thanks ...

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Martin