Dallmeyer produced fewer of the larger Portrait Petzvals, so that would account for the general lack of user reports on the web. I have the Dallmeyer 3A Patent Portrait and it's a beautiful lens, but very large, so if you're hunting for a 4A, you better have a studio camera. The 3A will cover 8x10 and you can fit it to an 8x10 field camera, but it doesn't quite fit on a 6"x6" lensboard. Even the 3A is a stretch for a field camera. As with any Petzval, you can use it for any purpose, but the controlling factor is format size relative to the focal length of the lens. It all comes down to the qualities you're looking for in a lens--zone of central sharpness, blur, swirl. If you're shooting wet plate, the speed is critical, but if you plan on using the lens with film, you might consider a slower (lighter, less expensive) Petzval.