Hi paul
The centre of the flower seems to be OK. But the edges are a bit out and the more I look the more it hurts my eyes
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Did you manually change the exposure between the 3 shots and reposition the camera each time? If you did then maybe you where at a slightly different angle each time you took a photo. The software will do its best but it will always have its limits. What software did you use?
Next time set the camera to bracket automatically. One stop on, one stop under and one stop over for starters and expand the range if you need. Also try using a tripod and if your camera does it, use the rapid repeat to reduce the time between shots and therefore any changes in position or light.
A good start though and this game is always about having a go and then working out how to do it better next time.
Have fun
Debs