Possible Canon 55-250 IS STM Decentering Issue

So, i recently bought a new lens for my 7D, the Canon 55-250 IS STM. Since i am a bit pedantic with my equipment, i have been testing the lens all night. However, i have had a bit of a problem with determining if my lens has misaligned optics.

To test the issue i took a handheld photo of a nearby apartment building wall at a distance from my balcony(since i do not own a tripod). The photos were taken using a 250mm focal length, aperture of f/5.6(which is the largest), AV mode, spot AF(PDAF) and the center AF point. The camera was probably not parallel to the wall.

The photos below show the entire image and crops(not uniform) from all 4 corners, top to bottom, left to right.

The problem is that i don't know how to interpret the data. What is an acceptable difference in sharpness between the corners? It is evident that the top of the frame exhibits more chromatic aberration, with the left corner being the worst in terms of sharpness and CA. Is this difference just the result of the conditions in which the photograph was taken, or could it be that the lens has a decentering issue? Could/Would an exchanged lens perform better optically? Does this make a difference in real life shooting?

Any conclusions, tips or opinions would be of great help to me.

Complete Image

Top Left Crop

Top Right Crop

Bottom Left Crop

Bottom Right Crop

Thanks for the tip!

I ran it through 50% DLO in DPP 4, making the flaws much more apparent.

Here are crops of the best(top left) and worst corner(bottom right). In my opinion the upper left corner looks more distorted. Is this normal? Could it just be an effect of my handheld shot, since the camera probably wasn't parallel with the wall?

Top Left Corner Crop

Bottom Right Corner Crop

skogsfaktor wrote:

So, i recently bought a new lens for my 7D, the Canon 55-250 IS STM. Since i am a bit pedantic with my equipment, i have been testing the lens all night. However, i have had a bit of a problem with determining if my lens has misaligned optics.

To test the issue i took a handheld photo of a nearby apartment building wall at a distance from my balcony(since i do not own a tripod). The photos were taken using a 250mm focal length, aperture of f/5.6(which is the largest), AV mode, spot AF(PDAF) and the center AF point. The camera was probably not parallel to the wall.

The photos below show the entire image and crops(not uniform) from all 4 corners, top to bottom, left to right.

The problem is that i don't know how to interpret the data. What is an acceptable difference in sharpness between the corners? It is evident that the top of the frame exhibits more chromatic aberration, with the left corner being the worst in terms of sharpness and CA. Is this difference just the result of the conditions in which the photograph was taken, or could it be that the lens has a decentering issue? Could/Would an exchanged lens perform better optically? Does this make a difference in real life shooting?

Any conclusions, tips or opinions would be of great help to me.

Looks quite ok. Serious decentering would look worse.

skogsfaktor wrote:

Thanks for the tip!

I ran it through 50% DLO in DPP 4, making the flaws much more apparent.

Here are crops of the best(top left) and worst corner(bottom right). In my opinion the upper left corner looks more distorted. Is this normal? Could it just be an effect of my handheld shot, since the camera probably wasn't parallel with the wall?

Top Left Corner Crop

Bottom Right Corner Crop

hmm, to me, the bottom right looks better.   That's the point, if we can't agree on this, it can't be a serious issue.  And anyway, if you want to look for small differences, yes, you need to take it to another level, and do very careful tests with test charts, with well calibrated and aligned equipment.

there are several articles online that shows a quick way to test if the lens is decentered, just google it, but for a 400mm equiv lens on crop body, super lightweight for <$150...cant really complain!