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Stellar lens, no weak spots

Started Oct 13, 2021 | User reviews thread
Sittatunga Veteran Member • Posts: 5,406
Re: A weak spot
3

FingerPainter wrote:

gimp_dad wrote:

FingerPainter wrote:

dmanthree wrote:

Leigh A. Wax wrote:

There is nothing man made that is of such utter perfection that it has "no" "weak" points!

I never said perfect. There is a huge difference between an optical imperfection, which all lenses have, and a weak spot. A weak spot, such as softness at a certain focal length and aperture combination would force you to NOT use that setting. That's what I consider a weak spot. You do not need to compensate for this lens.

Well the edges (not even corners) at f/4 and f/5.6 at 100mm are so weak I certainly would be forced not to use this lens for certain shots.

If, as you seem to admit, you haven't even tested for this, or for field curvature at a number of subject distances, you are in no position to make a claim of "no weak spots".

I’m not seeing softness near the edges at 100mm with my copy of the RF70-200/4LIS. FingerPainter, can you share your examples of this phenomenon? I wonder if you have a bad copy.

I also haven’t observed field curvature but the aperture is not wide enough for that to show up easily for me given how I usually choose my focus points.

Check online reviews that actually measure lens sharpness.

I'm confused. Wouldn't it be easier to present the results of your own tests for this, or for field curvature at a number of subject distances than to tell people to check unspecified online reviews? Relying on other people's impressions means you can't criticise the OP for not testing for these criteria.  You're saying "Prove it" while not proving your own assertions.

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