Why is North American Douglas Fir good for painting outdoors?

Douglas fir is a very resinous timber grown in harsh climates with hot sunny summers and brutally cold winters. The North American variety is a fine grain texture and tends not to splinter as much as other timbers. It is also very clear of knots which makes it a lot more consistent for painting.

Why is Idigbo good for outdoor painted joinery?

Idigbo is naturally resiliant to wet conditions so it is good for external use. What makes it ideal for painting is its straight fine grain texture and that it is consistentlly clear of knots.