My Lomography Petzval lens sits on my Canon 5d Mk iii. (http://shop.lomography.com/us/lenses/brass-petzval-canon-mount)  That is an interesting combination of old and new technology.  I bought the lens on impulse in Paris last year as I was getting ready for several shoots.  That was not smart but it worked out okay.  Since that time I have tweaked my technique to allow me a much higher incidence of properly focused images.  This is the first of a few blogs which will share my techniques in hopes they will be helpful to others.