Opencv cv::Subtract method throwing System.Runtime.InteropServices.SEHException Exception - c++

Question

I am currently trying to implement the Lucy Richardson algorithm in Opencv, when it comes to running the 'cv::subtract' method in my program it throws an InteropServices exception (stack trace below)
************** Exception Text **************
System.Runtime.InteropServices.SEHException (0x80004005): External has thrown an exception.
at cv.Mat.=(Mat* , MatExpr* expr) in e:\opencv\opencv\build\include\opencv2\core\mat.inl.hpp:line 3107
at LucyRichardson.LucyRich(LucyRichardson* , Mat* , basic_string<char\,std::char_traits<char>\,std::allocator<char> >* imagePath) in e:\documents\development\realtimeimageprocessing\imageprocessing\imageprocessing\lucyrichardson.cpp:line 63
Below is the block of code where the error occurs, it is thrown on the second line.
im_correction = cv::Mat (cvSize(383, 357), 8, 1);
cv::subtract(im, im_conv_kernel, im_correction);
cv::namedWindow("Sub");
cv::imshow("Sub", im_correction);
The variables im and im_conv_kernel are both of type cv::Mat and are correctly populated and the variable im_correction I have tried creating a version of before I save the result of the subtraction in.
I am using cv::subtractions fine in other parts of the program.
Does anyone know why this error occurs and how I could fix it? Or if there is a different method I could try for the subtraction?

Answer 1

I have worked out where the problem was I needed to make sure all of the images where of the same type. - After adding the below three lines before performing the subtract it worked fine.
im.convertTo(im, CV_8UC1);
im_conv_kernel.convertTo(im_conv_kernel, CV_8UC1);
im_correction.convertTo(im_correction, CV_8UC1);