I shoot real estate every day and I use the K-1 with the DF-A 15-30 and it is a great combination. I thought about the Irix 15mm for the size and weight and also because it’s a prime lens all good features to be sure, but in the end I went with the 15-30.
The 15-30 weigh more and is bigger than the Irix but I have not had any problems carrying the 15-30 around any house. All in all, I am very happy with my choice of the 15-30.
Also as Dericali said I do use the zoom a lot depending on the shot I am trying to get.
Below are a few photos taken the other day.
All photos taken with a K-1 and 15-30