Flash for the Nikon D40.
Built-in Flash Yes.
This camera does not support HSS.
This camera does not support Nikon Creative Lighting System CLS even if Nikon website says it does, it does not.
Flash Compensation -3 to +1 EV in increments of 1/3 EV
For me, this is what stands out in the Nikon D40 vs other DSLR cameras.
The Nikon D40 is one of the few Nikon DSLRs cameras that supports 1/500s flash sync speeds when most cameras can only go 1/250s flash sync speed.
You may ask, why is this important?
Shooting in harsh bright sunlight, for example, it could help you to get the fill flash just right, you can also shoot at larger apertures, which gives you more depth-of-field, you can use a cheaper speed-light that does not support HSS, But the problem is, the camera can only go minimum of 200 ISO, when most cameras can go as low as 100 ISO, but 1/500 flash sync shutter speed could still help you a lot in some situations.
I think it’s best to go for a cheaper flash when I have such old camera, I recommend this small flash from MEIKE its TTL and works very well with this camera.