I will soon list some Limited lenses for sale. This is not that post. This is a post about the best way(s) to test and demonstrate the sharpness (or softness) of a lens.
The 35mm Limited I wanted came bundled with two other Limited lenses I already had. So now I have 2x DA 70mm and 2x DA 15mm.
I find myself in the unusual position of being able to compare 15mm vs 15mm and 70mm vs 70mm to see if there are any significant differences between them. What I have found is that the biggest difference is not between my two copies of a lens. The biggest difference is between shots taken focusing in "from infinity" and focusing out "from close-up". Both of my 70mm Limited lenses perform well ONLY when they focus "in" from infinity. They deliver poorly-focused results when they focus "out". The difference is so great that it might change my whole photographic technique if this keeps up.
I set up a test target on a sunlit patch of cobblestones near the office. Tripod, 2-second timer with mirror lock-up, sunny day. I had to use a CPL filter due to the midday sun. I don't like introducing that variable, but I took note of the CPL angle. Center focus point, pattern metering. Three shots at f/2.8 to test depth of field, bokeh, and field curvature. Three shots at f/5.6 to test overall sharpness and corner brightness. Before every shot, I defocused the lens and refocused it using the center AF point of my K200D. (I recognize that field curvature is hardly an issue with a 70mm lens, but it's practice for when I test my two 15mm lenses.)
At first, my 70mm Limited really seemed to struggle at f/2.8. I was very disappointed. This is the
best of three test shots, each one a fresh AF lock after I focused on my nearby hand:
Poor. Lens is backfocused. I would only sell it with a disclaimer and a discount.
But then, I tried three more shots. This time, I manually set the lens to a distant focal point and then used AF before each shot. This is the best of three such shots:
Very good. Lens is fine.
For a side-by-side comparison:
I did these tests on my lunch break, using my work camera, a K200D. That camera does not have any lens adjustment abilities, so a backfocused lens is no good to me. (I do have a more capable K-S2 at home, but I want lenses that work well on both bodies.) Am I testing things correctly? Any advice?