My knowledge of the advances in photography in the 1840's (which I assume is the period for your coaches and pictures) is sketchy, but did they not use glass plates and would have been taken by keen amateurs or professionals? Or perhaps they were engravings?.
I discovered some 1890 to 1894 plates at work which were chrystal clear, and capable of 4X magnification without loss of detail (they're now in Derby Industrial Museum).
I think the loss of detail and/or blurring is due to the limitations of the (news) printing processes of the time which, I believe, entailed engraved copper plates for pictures, and subsequent copying and/or magnification.
However I do like the effect you have achieved, and I do like your Farthing epistles.
Cue..a correction by someone much more knowledgable!!