Defect Flash incompatiblity with Coolpix 5400.
The Coolpix 5400 will not produce satisfactory photographs in flash mode with the Wide Angle Converter lens fitted because the lens blocks the cameras photocell sensor.
The lens also blocks the cameras inbuilt flash giving a shadow.
There is no obvious indication of this problem in the sales literature.
The problem is only partially resolved by using a Nikon SB 800 Speedlight.
The Nikon SB 800 Speedlight instructions for the Coolpix 5400 recommend using a TTL setting with the Coolpix 5400.

This is fine, but unfortunately does not work with Wide Angle Converter lens fitted.
The problem once again is the position of the cameras photocell.
Manual flash operation can be achieved by setting the flash gun to A and then manually setting up features on the camera such as aperture.
The automatic point and shoot features of the 5400 in this Auto Mode are then incompatible together with use the camera in Scene Mode. Features such as automatic flash operation under low light conditions and the other flash features that form part of the cameras operation in these modes with the standard lens are also lost.
Amazon may wish to warn customers thinking of purchasing the Wide Angle Converter of these problems.
NB the lens and camera are excellent except when it comes to flash operation.
Have raised the issue with Nikon Technical and have suggested if they can not resolve the problem by electronic means that they should provide a simple optical periscope arrangement for the Coolpix 5400 so that the photocell on the camera can then see over the wide angle Converter.
Have also suggested they might achieve something similar with an optical fibre accessory.
It is a great shame that this outstanding camera and its lens system is spoilt by this issue.
No doubt Nikon with their reputation for service and quality will swiftly provide purchasers who wish to use the wide angle converter with their Coolpix 5400 with a fix.