Hi Tim, In doing some exploring between Fractint and Ultrafractal, I have found what I think are some errors in Fractint. The first one involves MarksMandel. The error here is in the documentation. The documentation has the formula as z -> (c^exp-1)*z^2 + c It should actually be z -> c^(exp-1)*z^2 +c This can be readily verified by coding both ways in Ultrafractal and comparing to the built-in MarksMandel formula in Fractint. The other apparent error is for the built-in Hypercomplex formula with the function being sqr. If cj = 0.1 or ck = 0.1 the image agrees with what I get in my UF formula using your hypercomplex code. If BOTH cj = 0.1 and ck = 0.1, the images are different. The built-in Fractint formula forces symmetry around the x axis, and the correct image is not symmetrical. Cheers, Ron Barnett