Defective Oly 25mm lens

Betarover wrote:

Some here have suggested I test this lens by photographing a sheet of paper. I do landscapes and for me such a test may not be useful. Consider the geometry. If a sheet of paper is photographed, the edges, and especially the corners, would be at a slightly greater distance from the lens than the center. If the lens is engineered to compensate for this small difference in distance when it is focused near, has it been correctly engineered for a flat plane when focused on infinity? Are the elements within the lens engineered correctly so that they move relative to each other in a way that allows both near and distant images to be sharp, corner to corner? How can one be sure, except by photographing a distant landscape where all elements are so distant as to be considered at infinity?

Another posting feels I am expecting too much from this lens. Not so. The image below shows that my Panasonic 14-45mm zoom is much sharper on the left. Clearly the Oly 25mm is a defective lens, and I am "pleased" that others have posted here having had the same experience.

The intent of this thread is to alert others that there are bad lenses out there and if edge to edge sharpness is wanted, one should be afraid to buy from a source not giving a satisfaction guarantee.

The images below show the scene, edge to edge across the middle, for my Panasonic 14-45mm and the defective Olympus 25mm. Each was taken at their sharpest f stop, and both are taken in the Hi-Res mode.

Images taken with Oly EM5 Mk 2, Hi-Res mode.

Compare f/5.6!  Of course there is more DoF for the 14-45 case.  This test is also meaningless.  The left side detail is much closer than your focus point.  It is meaningless to compare sharpness for ANYTHING except at the focus distance.  If you want to compare, zoom in to the left edge and manually focus to optimal sharpness and then compare.  When looking at 100%, there is NO depth of field.  It is all out of focus except for exactly one distance, and that distance varies over the image surface.

I said you are expecting too much because the Olympus 25/1.8 is simply NOT a great lens.  Perhaps every now and then, somebody gets incredibly lucky with a great copy, but I doubt very much that your copy is out of spec.

It does not review well, and it isn't stellar.  That's why it is also cheap.  For that matter, Nikon and Canon 50mm f/1.8 lenses are designed to be cheap and aren't all that great, even in the new Nikon G version or the Mk II version from Canon.  They are OK, but they aren't pro lenses.

I picked up the Panasonic 25mm f/1.7 @$99 (two copies, actually), and they are both OK.  Not great; not terrible, but OK.  For the price, I'm happy.  I wasn't expecting a pro lens.  Don't confuse this lens with the Olympus 45/1.8, 12/2, 75/1.8, etc.  It is not in the same league (as is the case for the 17/1.8).