Choderboy wrote:
I agree, not good subjects for testing.
Brick wall type test better. Not an actual brick wall, but, like a test chart, 2 dimensional.
You can try an actual brick wall, but you'll need to be quite close with a 15mm lens, so your are only testing at a very short distance.
If you stand further back, with the camera level, half the shot will be the ground.
So turn the camera upside down and take another shot.
Spots: they are on the sensor. It looks more like 13 or more to me.
There are probably more that you can't see, in the lower half of the shot.
If you just pointed at the sky, you'd see them.
I used that subject because the two top edges, you can compare the leaves to the leaves closer inward. To me, the edges/leaves are not anywhere near as sharp as the leaves closer inward.
I took a photo of a rough stucco wall but there is a fair amount of vignetting where the edges are very dark.
" you can compare the leaves to the leaves closer inward."
What is 'closer inward' ?
Better to use Centre, mid, edges, extreme corners. Also foreground, background.....
While I maintain that I don't think your photos are useful for testing, at 1000 pixels x 666 pixels and less than 100kB,
they are simply too small to be useful as posted, other than to show the scene used.
He shows the full scene and where he cropped the various examples from.
He uses: CENTER, MID-FIELD, CORNER, EXTREME CORNERS to describe them.
Then he posts 800x800 pixel crops. A bit smaller than what you posted, but his are 100% crops, the area cropped is about 1% of the entire scene, so they are very useful.
I like brick walls for testing. I have one at my office that is 10' tall x 15' wide. This gives a distance that is a bit beyond what you would use for a full body portrait. I adjust the distance for focal length so the same section of wall is used in all tests. This provides info that can be compared across focal lengths.
I also like to test at further distances, we have a stadium that seats 70,000 with brick sides. This is fairly close to an optical infinity. I also use a parking garage that is next to a brick building. The 3rd floor of the garage is about midway up the building and this gives a test that is about 85' away.
One of the things I have found really helpful is a rock solid tripod and getting 240MP pixel shift images. The high resolution images really help to learn the weakness of the lenses. You might not want to know, sometimes ignorance is bliss. But it you are OK with knowing the truth about the lens this will reveal the strength or weakness of the lens.
