Aperture stop down failure with Samyang 12mm fisheye

MJKoski · 02-23-2017, 03:46 AM

Does any of you use Samyang 12mm fisheye? On tuesday I was shooting star trails @ -11C temp and after 128 frames I stopped shooting for few minutes to adjust lighting for few foreground items. After I took the final few exposures I noticed that light levels were way off in the last few photos. The lens was not stopped down to f/6.3 like for the first series of exposures but was left wide open no matter what aperture I dialed in.

These Samyang K-mount lenses have A-lens functionality for automatic aperture setting by camera body. So, which is going now? Aperture actuation lever of K-1 or the Samyang?

Not a Number · 02-23-2017, 03:57 AM

The specs for the K-1 list the low operating temperature as -10°C so I would guess that the reason is your system got too cold.

Do things work fine after bringing the equipment indoors and letting it warm up to room temperature?

MJKoski · 02-23-2017, 04:46 AM

Yes it works now when warmed up. But, it worked month ago @ -32C just fine. My guess is there is some sticky lubricant on the aperture blades of the Samyang. Gonna return it anyway for bad centering of optics.

02-23-2017, 03:46 AM	#1
MJKoski Veteran Member Join Date: Aug 2016 Posts: 1,784	Aperture stop down failure with Samyang 12mm fisheye Does any of you use Samyang 12mm fisheye? On tuesday I was shooting star trails @ -11C temp and after 128 frames I stopped shooting for few minutes to adjust lighting for few foreground items. After I took the final few exposures I noticed that light levels were way off in the last few photos. The lens was not stopped down to f/6.3 like for the first series of exposures but was left wide open no matter what aperture I dialed in. These Samyang K-mount lenses have A-lens functionality for automatic aperture setting by camera body. So, which is going now? Aperture actuation lever of K-1 or the Samyang?

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02-23-2017, 03:57 AM	#2
Not a Number Moderator Join Date: Mar 2012 Location: Venice, CA Posts: 10,526	The specs for the K-1 list the low operating temperature as -10°C so I would guess that the reason is your system got too cold. Do things work fine after bringing the equipment indoors and letting it warm up to room temperature?

02-23-2017, 04:46 AM	#3
MJKoski Veteran Member Join Date: Aug 2016 Posts: 1,784 Original Poster	Yes it works now when warmed up. But, it worked month ago @ -32C just fine. My guess is there is some sticky lubricant on the aperture blades of the Samyang. Gonna return it anyway for bad centering of optics.