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Used lens: diaphragm iris not perfectly circular
#1
I've spotted a defect of the Samyang 75mm F1.8 lens that I bought a few days ago: the diaphragm iris is not perfectly circular. The defect worsens as far as you stop down. With the limited testing I've done so far, it has apparently no effect on photos — clearly it would affect the shape of bokeh balls, but at least up to ƒ/8 it's not noticeable (I will try to specifically test with point of lights to get more info).
Can it cause other problems? Would you keep a lens with this defect or return it?
Thanks.

Added: what about the fact that the defect could be a sign of a potential failure in future?


Attached Files
.jpg   Screenshot 2023-09-22 at 12.18.38.jpg (Size: 257.05 KB / Downloads: 9)
stoppingdown.net

 

Sony a6300, Sony a6000, Sony NEX-6, Sony E 10-18mm F4 OSS, Sony Zeiss Vario-Tessar T* E 16-70mm F4 ZA OSS, Sony FE 70-200mm F4 G OSS, Sigma 150-600mm Æ’/5-6.3 DG OS HSM Contemporary, Samyang 12mm Æ’/2, Sigma 30mm F2.8 DN | A, Meyer Gorlitz Trioplan 100mm Æ’/2.8, Samyang 8mm Æ’/3.5 fish-eye II | Zenit Helios 44-2 58mm Æ’/2 
Plus some legacy Nikkor lenses.
#2
Actually, with a bright light point I can see that the defect is more visible than I thought...


Attached Files
.jpg   Screenshot 2023-09-22 at 13.30.47.jpg (Size: 443.73 KB / Downloads: 9)
stoppingdown.net

 

Sony a6300, Sony a6000, Sony NEX-6, Sony E 10-18mm F4 OSS, Sony Zeiss Vario-Tessar T* E 16-70mm F4 ZA OSS, Sony FE 70-200mm F4 G OSS, Sigma 150-600mm Æ’/5-6.3 DG OS HSM Contemporary, Samyang 12mm Æ’/2, Sigma 30mm F2.8 DN | A, Meyer Gorlitz Trioplan 100mm Æ’/2.8, Samyang 8mm Æ’/3.5 fish-eye II | Zenit Helios 44-2 58mm Æ’/2 
Plus some legacy Nikkor lenses.
#3
I forwarded your photos to an expert (Canon repairs guy) there's nothing to worry about
#4
Thanks Toni.
stoppingdown.net

 

Sony a6300, Sony a6000, Sony NEX-6, Sony E 10-18mm F4 OSS, Sony Zeiss Vario-Tessar T* E 16-70mm F4 ZA OSS, Sony FE 70-200mm F4 G OSS, Sigma 150-600mm Æ’/5-6.3 DG OS HSM Contemporary, Samyang 12mm Æ’/2, Sigma 30mm F2.8 DN | A, Meyer Gorlitz Trioplan 100mm Æ’/2.8, Samyang 8mm Æ’/3.5 fish-eye II | Zenit Helios 44-2 58mm Æ’/2 
Plus some legacy Nikkor lenses.
  


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