SMC 50mm f/1.4 issue when stopped down.

JT322 · 02-16-2019, 03:29 PM

Hi I’ve been using this lens, the overall condition looks very good, however when I use an aperture between f/8 - f/22 I get two small black spots in my images, everything from f/1.4 - f/8 is perfect. What could cause this? I can’t visibly see any dirt or marks in the glass.
Thanks for any information.

It’s Not a huge issue when using it on my digital camera but kind of a pain to shoot film now. I have to keep a cpl on to keep lower f stops.

photoptimist · 02-16-2019, 04:01 PM - **1 Like**

This sounds like dust on the sensor.

Try a different lens set to f/22. I'd bet you'll get the same spots in the same places on those images, too.

JT322 · 02-16-2019, 05:59 PM

Originally posted by photoptimist

This sounds like dust on the sensor.

Try a different lens set to f/22. I'd bet you'll get the same spots in the same places on those images, too.

When I use my digital Olympus Micro 4/3 lenses I have zero issues it’s not my camera it’s that particular lens.

Not a Number · 02-16-2019, 09:03 PM - **1 Like**

I wouldn't be too sure about that. I've had dust on my sensor that is barely noticeable with some focal length lenses and very apparent with others. There was just a person that had oil drops on his/her sensor and the artifacts showed very clearly with one lens but not others. Professional cleaning of the sensor solved that problem.

Anything on the lens itself that projects a noticeable shadow on the sensor would have to be fairly significant and should be very visible. Try shining a light through the lens (check both ends). If there is something there you should see it.

If you still don't see anything examine you sensor with a strong light.

stevebrot · 02-17-2019, 05:58 PM

Welcome to the Pentax Forums!

Originally posted by JT322

when I use an aperture between f/8 - f/22 I get two small black spots in my images, everything from f/1.4 - f/8 is perfect

What you describe is typical for dust or similar on the sensor. Does your camera have a dust detection feature? If so, what does it report? For peace of mind, you might want to physically inspect your lens for dirt using a small flashlight in a dim room. Shine the light at an oblique angle into the front of the lens while looking through the lens from the rear. Repeat from the other direction. Any dust, dirt, fungus, or scratches should be readily visible.

Steve

JT322 · 02-17-2019, 08:38 PM - **1 Like**

I went ahead and just cleaned my sensor and problem solved lol, thanks for the advice. Glad it wasn’t my lens it’s my favourite!

02-16-2019, 03:29 PM	#1
JT322 New Member Join Date: Feb 2019 Location: Niagara Falls Canada Posts: 4	SMC 50mm f/1.4 issue when stopped down. Hi I’ve been using this lens, the overall condition looks very good, however when I use an aperture between f/8 - f/22 I get two small black spots in my images, everything from f/1.4 - f/8 is perfect. What could cause this? I can’t visibly see any dirt or marks in the glass. Thanks for any information. It’s Not a huge issue when using it on my digital camera but kind of a pain to shoot film now. I have to keep a cpl on to keep lower f stops.

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02-16-2019, 04:01 PM - 1 Like	#2
photoptimist Pentaxian Join Date: Jul 2016 Photos: Albums Posts: 5,129	This sounds like dust on the sensor. Try a different lens set to f/22. I'd bet you'll get the same spots in the same places on those images, too.

02-16-2019, 05:59 PM	#3
JT322 New Member Join Date: Feb 2019 Location: Niagara Falls Canada Posts: 4 Original Poster	Originally posted by photoptimist This sounds like dust on the sensor. Try a different lens set to f/22. I'd bet you'll get the same spots in the same places on those images, too. When I use my digital Olympus Micro 4/3 lenses I have zero issues it’s not my camera it’s that particular lens.

02-16-2019, 09:03 PM - 1 Like	#4
Not a Number Moderator Join Date: Mar 2012 Location: Venice, CA Posts: 10,526	I wouldn't be too sure about that. I've had dust on my sensor that is barely noticeable with some focal length lenses and very apparent with others. There was just a person that had oil drops on his/her sensor and the artifacts showed very clearly with one lens but not others. Professional cleaning of the sensor solved that problem. Anything on the lens itself that projects a noticeable shadow on the sensor would have to be fairly significant and should be very visible. Try shining a light through the lens (check both ends). If there is something there you should see it. If you still don't see anything examine you sensor with a strong light.

02-17-2019, 05:58 PM	#5
stevebrot Otis Memorial Pentaxian Join Date: Mar 2007 Location: Vancouver (USA) Photos: Gallery \| Albums Posts: 42,007	Welcome to the Pentax Forums! Originally posted by JT322 when I use an aperture between f/8 - f/22 I get two small black spots in my images, everything from f/1.4 - f/8 is perfect What you describe is typical for dust or similar on the sensor. Does your camera have a dust detection feature? If so, what does it report? For peace of mind, you might want to physically inspect your lens for dirt using a small flashlight in a dim room. Shine the light at an oblique angle into the front of the lens while looking through the lens from the rear. Repeat from the other direction. Any dust, dirt, fungus, or scratches should be readily visible. Steve

02-17-2019, 08:38 PM - 1 Like	#6
JT322 New Member Join Date: Feb 2019 Location: Niagara Falls Canada Posts: 4 Original Poster	I went ahead and just cleaned my sensor and problem solved lol, thanks for the advice. Glad it wasn’t my lens it’s my favourite!