p.5 #5 · FM Lens test for Centering (Mount tilt / swing)
High shutter speeds are necessary for ruling out camera shake if the test is done handheld. 1/3200s is good. It also doesn't need to be done wide open (and sometimes stopped down is advantageous to reduce aberrations), though it usually doesn't hurt.
More importantly, what is your intended usage? I'm assuming it's not strictly for landscape. If your intended use is portraits at or near wide open and landscapes, etc stopped down, then I would be happy with this result--especially with a lens this problematic.
p.5 #7 · FM Lens test for Centering (Mount tilt / swing)
DaveFP and Sharpedon,
Not sure what I'm missing.
I thought the FM method was to shoot in bright light, so a fast shutter can be used, therefore no camera shake. Plus shooting at infinity eliminates any alignment issues. There's no camera shake in these images.
Is it not the intent to check for de-center(or tilt) by shooting wide open. Stopping down hides the issues at the edge of the lens. I'm pretty sure all lenses sharpen up as you stop down, to a point. At some point diffraction will affect image sharpness.
That's how I read FM's method. Personally, I've had some success setting up a home test ala Roger Cicala' method. You clearly need to pay attention to alignment, but it's not that hard. And a slightly out of focus zeiss star is pretty useful.
p.5 #8 · FM Lens test for Centering (Mount tilt / swing)
Yes these are 100% crops. The sequence of the pictures follows Fred's 1,2,3,4 sequence. It also said "The lens aperture should be set at least 1-stop down from wide open to minimize lens aberrations." which is why I didn't shoot it wide open. I'll try some at f/1.8 tomorrow.
p.5 #10 · FM Lens test for Centering (Mount tilt / swing)
OK, I reshot my Sony 35 f/14 Distagon wide open at f/1.4 and 1/8000s.
The right seems softer with the bottom right being the worst.
Shooting at f/1.8 shows the same thing.
My question is, how bad is this? Should I send it back? Typical use of this lens is going to photojournalistic uses: people in their surroundings/context and other some street shooting.
p.5 #11 · FM Lens test for Centering (Mount tilt / swing)
sanjeevdas,
Those results are similar to my 85mm f/1.4GM. Those images are on page 4 of this thread. Same price point too.
I would go shoot it as you intend to use it, then look at your images and see if you still like it.
If not, return it, for another copy if you can.
It's clearly soft on the bottom right. My GM is too.
I've seen other reference on this site that say, go shoot it like you want to use it.
By the way, did you turn off IBIS?
Good luck.
Here are some quotes from FM earlier in this thread:
"I don't think we can really say what's acceptable or not for someone else. Element decentering or tilt affects the entire image field but are more noticeable towards the extreme edges of the frame. For this reason, I prefer testing the very corners for similarity, knowing that a great number of lenses won't have equal corner resolution.
Some applications demand more from our lenses and I don't see any harm in knowing how our copies stand. Personally, I believe this is a very demanding test and therefore, I consider lenses that are a bit off still keepers."
"From my experience, it really depends on the lens. With modern primes, I usually test wide open as well.
Some lenses, especially vintage ones need at least one stop for the corners to come alive and resolution to show a pulse. If the corners are mushy, it's harder to evaluate centering."
p.5 #15 · FM Lens test for Centering (Mount tilt / swing)
Good day sanjeevdas,
I'm using the texture of the rock planter wall on the right side of the home.
The new lens does seem sharper, only slightly though, but it's better than the images previously.
My 85mmGM was way softer in the bottom right corner when compared to yours.
With that said, it is so subjective. Other than sending it to Lens Rentals and asking/paying them for their opinion I don't know what else to say.
These are mass produced to a specific tolerance. My guess it's within that spec.
I kind of agree with the idea to go out, shoot images, like the lens was intended to use (portraits, landscape, astro....whatever) and see if you like the results.
IMO, I'd shoot this lens, it is as consistent/sharp as my 55mm f/1.8.
Hope you enjoy your holiday and can get out to shoot.
p.5 #16 · FM Lens test for Centering (Mount tilt / swing)
Want to get some advice here.
I sent my Sony 24-105mm lens for calibration at Sony Service Center last week and they have just sent me these three charts (taken at 24mm, 50mm, 105mm F4.0) after calibration was completed. Do they look acceptable? Appreciate your comments.
p.5 #17 · FM Lens test for Centering (Mount tilt / swing)
I've created a tool that should help to minimize the effort of lens decentering tests. The instructions are slightly different from those given by Fred, but the result should be the same.
The tool runs in your browser (Chrome and Firefox tested).
You can try it here:
p.5 #18 · FM Lens test for Centering (Mount tilt / swing)
keepcoding wrote:
I've created a tool that should help to minimize the effort of lens decentering tests. The instructions are slightly different from those given by Fred, but the result should be the same.
The tool runs in your browser (Chrome and Firefox tested).
You can try it here:
Since lenses have more or less field curvature, it doesn't suffice to focus in the middle and then tilt the camera to the 4 corners, leaving focus as is. With the subject in each corner, you have to focus anew (preferable via manual focusing via focus magnifier in EVF) to optimum sharpness each time. The degree to which this optimum achievable sharpness is different in each corner tells you the degree of decentering.
p.5 #19 · FM Lens test for Centering (Mount tilt / swing)
hasenbein wrote:
Not suitable.
Since lenses have more or less field curvature, it doesn't suffice to focus in the middle and then tilt the camera to the 4 corners, leaving focus as is. With the subject in each corner, you have to focus anew (preferable via manual focusing via focus magnifier in EVF) to optimum sharpness each time. The degree to which this optimum achievable sharpness is different in each corner tells you the degree of decentering.
What you suggest is tedious and will shy away most users from doing a test in the first place.
Maybe for some lenses it is necessary to refocus. However, in my experience most (modern) lenses don't exhibit a significant field curvature at infinity, so my method works just fine.
For a basic decentering test you don't need pinsharp corner crops, just need to make sure the resolution in all corners is comparable.
p.5 #20 · FM Lens test for Centering (Mount tilt / swing)
keepcoding wrote:
I've created a tool that should help to minimize the effort of lens decentering tests. The instructions are slightly different from those given by Fred, but the result should be the same.
The tool runs in your browser (Chrome and Firefox tested).
You can try it here:
Just checked out your github project. wanted to let you know this looks cool. I'll play around with it at some point soon. Thanks for making that tool.
