I just did a post on the Lensbaby Sol 45 and decided to do a comparison post for you showing the differences it offers vs the Lensbaby Sweet 50… which is the lens most people will compare this to when asking how is it different and why would they want one or the other or perhaps both.
The biggest differences in the 2 lenses as I see it:
Sol45 has a larger circle of focus area
Sol45 has less blur and it is a creamier blur not distorted blur like the Sweet 50
Sol45 has a fixed f3.5 aperture where the Sweet 50 has a variable aperture from f2.5-f22
Sol45 is a stand-alone tilt lens with a very small tilt ratio compared to the Composer system.
Sol45 is significantly easier to find your focus than the Sweet lenses in my opinion.
Sol45 has the bokeh blades you can use which is unique to this lens.
Overall I’d say there is good reason to have both lenses in your bag. There is no real comparison to the photos each lens produces. They are significantly different in the effects they offer and the photos you end up with. You can check out my lens test shots of each scene below. You’ll notice on the Sweet 50 photos there is a tighter spot of focus and a more blur. I was trying to set up the scenes so they were as similar to each other as possible to really show the difference each lens offers.
*These photos were processed with the Euphoria preset collection.