I was thinking about buying a 28mm lens for one of my cameras, but, I didn't want to sink a lot of money in a lens I might not use much (something I have done in the past). I remembered I had bought a 28mm Soligor lens that would fit my Konica Autoflex TC a couple of yeas ago. Now Soligor lens are reputed to be cheap low quality lenses. If memory serves me correctly I paid $12 for this one. I also have a 40mm Konica Hexanon that is reputed to be very sharp. In fact many people are buying this lens and using it on Sony mirrorless cameras. I decided to put both lenses through their paces and see what happened. Now I don't shoot test patterns. I like my tests to be more like something I might shoot in real life. I went to Chatham National Monument a near by park.
First of field of view. Exactly how much wider is a 28mm than the 40mm. I like to use 40mm as a normal lens. Notthe usual 50mm lens, which, I find a little long in many situations. Standing in the same spot I took a shot with each lens F11 at 1/125 sec. hand held. Once scanned I put a black border on the 40mm image and imposed it over the 28mm lens image. I resized the 40mm to get a close match. This shows the wider field of view but really doesn't tell us much about sharpness.
The next shots were of a cannon with Chatham Manor in the back ground. First shot was with focus on muzzle of cannon and second shot was with focus on shutters on Chatham Manor. All shots were set at F11 1/125 sec. hand held. Again I put a black border on the 40mm lens image and imposed it over the 28mm lens to show field of view. Still doesn't tell us much about sharpness.
Next I cropped the muzzles and shutters where I focused the camera from each image and pasted them all on one image. Still a little hard to draw a conclusion. So I cropped the muzzle area and shutter area into images to show details.
The muzzle images: 28mm images on top row and 40mm images are on bottom row. First column images are focused on Chatham Manor the second column focus is on muzzle. Clearly the 40mm is the sharper lens.
The shutter images: Here the 28mm images are in first column and the 40mm images are in the second column. The images in the top row are focused on the muzzle of the cannon and the bottom row of images are focused on the shutters. Here things are much closer. The difference between the images where the focus is on the muzzle of the cannon are negligible. The images where the focus is on the shutters, the 40mm may have a slight edge but practically speaking there is no difference.
Conclusion: The tests give me more of a feel for how wide a 28mm lens is, but, I would need to shoot it some to really decide if it is something I would use of enough to justify the cost of another lens. Up close and personal the 40mm is the sharper lens, in the distance they are a dead heat. The Soligor lens did better than it's reputation would suggest.