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eggwah123

Dark upper corners using FE 35mm/1.8 in small aperture and infinity focus

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Just bought the lens. Test it and very happy until I noticed dark upper corners, worse in the left. It only show up at small aperture (eg F11 F16 F22)and focus at infinity. The smaller the aperture the worse.
its worst in my A7II. Less noticeable in the A7RII. No hood or filter attached.

Picture shown is taken by A7II:

any idea what’s the cause? Please help. Can see the dark corner in EVF while composing and focusing 

All camera have updated firmware.

 

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To me this doesn't seem normal: regular vignetting gets less when closing down the aperture, not worse. Also, regular vignetting should be fairly similar for all corners and should gradually reduce towards the center.

In some lenses RAW-files show dark corners like these, but this is by design due to barrel-distortion and a small image circle (after digital correction the image is fine). The FE35 f/1.8 however has very little distortion and you say the dark corners are also in the viewfinder, which should be corrected for distortion. Just to be sure, do double-check if distortion compensation is enabled in your camera.

Given your observation that it gets worse when closing down and focussing at infinity, to me it sounds like something at the rear side of your lens is obstructing light rays from hitting the sensor. A small aperture combined with infinity focus results in very parallel light rays hitting the sensor, making physical obstructions close to the sensor very visible (also used as a method to spot dust on the sensor).

Perhaps have a look at the rear side of your lens to see if you can spot anything irregular, like a loose/shifted baffle.

Edited by Pieter

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4 hours ago, Pieter said:

To me this doesn't seem normal: regular vignetting gets less when closing down the aperture, not worse. Also, regular vignetting should be fairly similar for all corners and should gradually reduce towards the center.

In some lenses RAW-files show dark corners like these, but this is by design due to barrel-distortion and a small image circle (after digital correction the image is fine). The FE35 f/1.8 however has very little distortion and you say the dark corners are also in the viewfinder, which should be corrected for distortion. Just to be sure, do double-check if distortion compensation is enabled in your camera.

Given your observation that it gets worse when closing down and focussing at infinity, to me it sounds like something at the rear side of your lens is obstructing light rays from hitting the sensor. A small aperture combined with infinity focus results in very parallel light rays hitting the sensor, making physical obstructions close to the sensor very visible (also used as a method to spot dust on the sensor).

Perhaps have a look at the rear side of your lens to see if you can spot anything irregular, like a loose/shifted baffle.

Checked. The rear end of the lens looks fine to me. Thanks for suggestions.

lens compensation is on for all parameters too. 

Edited by eggwah123

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I don't own this specific lens so can't double-check if other copies behave the same. Perhaps some other reader can?

I'd be pretty annoyed if this was my lens: sounds like the lens is engineered slightly too tight. If you still have warranty I'd check with the store if they can let you try another copy.

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5 minutes ago, Pieter said:

I don't own this specific lens so can't double-check if other copies behave the same. Perhaps some other reader can?

I'd be pretty annoyed if this was my lens: sounds like the lens is engineered slightly too tight. If you still have warranty I'd check with the store if they can let you try another copy.

Just received it two days ago. Will return it. But still want to know the cause and may be It’s a simple issue to resolve Without returning it.. Googled and found no one reported any similar issues. That’s strange or I am just exceptionally unlucky.

Anyone own this lens can run a test? F22 and focus at infinity. Any dark corners like the picture I posted above?

Edited by eggwah123

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Lenstip just tested this lens and, interestingly, their findings seem to agree with yours: when stopping down, in general the vignetting gets less but the extreme corners seriously lag behind. This causes the corners to stand out more in apparent darkness at small apertures. In their case however all corners are similarly dark, so there was something decentered in your copy.

https://www.lenstip.com/593.8-Lens_review-Sony_FE_35_mm_f_1.8_Vignetting.html

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10 hours ago, Pieter said:

Lenstip just tested this lens and, interestingly, their findings seem to agree with yours: when stopping down, in general the vignetting gets less but the extreme corners seriously lag behind. This causes the corners to stand out more in apparent darkness at small apertures. In their case however all corners are similarly dark, so there was something decentered in your copy.

https://www.lenstip.com/593.8-Lens_review-Sony_FE_35_mm_f_1.8_Vignetting.html

Returned it by post already. Hopefully Sony will admit the defect and tell me what is the defect. Unlikely though.

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