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Archive 2014 · Erratic behavior 75mm 1.8 aperture blades

  
 
RogerC11
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p.1 #1 · p.1 #1 · Erratic behavior 75mm 1.8 aperture blades


I bought this lens a couple days ago and noticed that when I was shooting, the aperture blades would erratically start stopping down. How far the lens stopped down would be based on how much light the camera was pointing at.

At first I thought maybe it was because I hit the live view button by accident and the lens was stopping down to compensate for a proper exposure. Today I confirmed that this lens started doing the same thing today even though I had not pressed the live view button. The LCD displayed the super control panel and everything seemed fine except the lens kept closing down the aperture blades and opening them automatically. The lens came in a sealed factory refurbished olympus box. What should I do?



Jun 30, 2014 at 07:33 PM
millsart
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p.1 #2 · p.1 #2 · Erratic behavior 75mm 1.8 aperture blades


As mentioned in the other thread about the same subject, this is normal behavior for a mirrorless camera.

The blades have to close down to limit the light hitting the sensor, unlike a DSLR where the sensor is covered by the shutter curtain.

Some lens have a more pronounced effect than others. Google the 25mm f1.4 "rattle snake" issue with those blades opening and closing to read about one of the worst offenders




Jun 30, 2014 at 08:56 PM
jhinkey
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p.1 #3 · p.1 #3 · Erratic behavior 75mm 1.8 aperture blades


Yes, normal behavior for the 75/1.8 and my 42.5/1.2. Too much light over-exposing the sensor if the aperture was wide open.

The only time this causes problems is when you want to shoot wide open, but it focuses closed down and you get some focusing errors.



Jun 30, 2014 at 09:20 PM
RogerC11
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p.1 #4 · p.1 #4 · Erratic behavior 75mm 1.8 aperture blades


So what is the reason for this to happen besides overexposing? Is it from the sensor heating up after multiple exposures? It doesn't close down when I first power up the camera and take a couple frames, but seems to occur after several frames later after power up. Powering down and then back on seems to "reset" the behavior also...at least temporarily.


Jul 01, 2014 at 07:22 AM
Jman13
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p.1 #5 · p.1 #5 · Erratic behavior 75mm 1.8 aperture blades


It's so the sensor doesn't get fried. Exposing the sensor to very bright light for extended periods of time (potentially several minutes to hours if you're shooting a lot in bright light) could damage it, so the blades stop down during live view to help protect it. They'll open up for the exposure (and usually for focusing) if you've got the aperture set wide.


Jul 01, 2014 at 07:58 AM
riotshield
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p.1 #6 · p.1 #6 · Erratic behavior 75mm 1.8 aperture blades


My E-P5 does this from time to time (and my E-PL5 had the same issue), not just with the 75mm but my other lenses as well. Normally the lens will stay wide open except when the shutter is pressed. When this issue occurs, the lens will emit a constant clicking sound of stopping down and opening up responding to the light, even if it's indoors. When I turn off the camera and turn it back on, the problem goes away. Not sure how to reproduce the problem, but it seems to happen (but not consistently) when there are big shifts in exposure.


Jul 01, 2014 at 09:09 AM
RogerC11
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p.1 #7 · p.1 #7 · Erratic behavior 75mm 1.8 aperture blades


Jman13 wrote:
It's so the sensor doesn't get fried. Exposing the sensor to very bright light for extended periods of time (potentially several minutes to hours if you're shooting a lot in bright light) could damage it, so the blades stop down during live view to help protect it. They'll open up for the exposure (and usually for focusing) if you've got the aperture set wide.

Im not in live view when it happens and it happens even if im not half pressing the shutter. I could just be holding it no buttons pressed and it still stops down based on light entering the lens.



Jul 01, 2014 at 09:13 AM
snapsy
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p.1 #8 · p.1 #8 · Erratic behavior 75mm 1.8 aperture blades


RogerC11 wrote:
Im not in live view when it happens and it happens even if im not half pressing the shutter. I could just be holding it no buttons pressed and it still stops down based on light entering the lens.


The sensor is always exposed (and likely charged) while powered on so the mechanism is in place regardless of whether a LV feed is visible on the LCD/EVF.



Jul 01, 2014 at 09:18 AM
Wilbus
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p.1 #9 · p.1 #9 · Erratic behavior 75mm 1.8 aperture blades


Actaully, you are always in live view with a mirrorless camera. Doesn't matter if you use the rear screen or the viewfinder, they are just different types of screens showing what is happening.

As stated before in the thread, a mirrorless cameras sensor is always exposed when the camera is on, this is how you can see anything on any screen. DSLR's on the other hand covers the sensor with both the shutter and the mirror (the mirror allows the picture to be reflected up through the viewfinder).

I've only experienced the issue with one lens and it's the Panasonic Leica 25mm which sometimes goes bananas. Not much to do about it I guess. Turning the camera off and on again sometimes helps.



Jul 01, 2014 at 09:22 AM
atwl77
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p.1 #10 · p.1 #10 · Erratic behavior 75mm 1.8 aperture blades


Wilbus wrote:
As stated before in the thread, a mirrorless cameras sensor is always exposed when the camera is on, this is how you can see anything on any screen. DSLR's on the other hand covers the sensor with both the shutter and the mirror (the mirror allows the picture to be reflected up through the viewfinder).

Just to expand on this, DSLRs also behave this way in live view mode. I point my Canon 5D Mark III with 50/1.2L at the window in live view mode and the aperture blades will stop down.

Different manufacturers have their own tolerances and sensitivities to it (how bright before they stop down, and how quick/slow they react to the changing light), but practically all manufacturers have this behavior in some way or another.



Jul 01, 2014 at 09:33 AM
Jonas B
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p.1 #11 · p.1 #11 · Erratic behavior 75mm 1.8 aperture blades


When using old adapted lenses this doesn't happen. (Naturally)
I've been using several different live cameras since the original Panny G1 was released - but never fried a sensor. Maybe thanks to usually carry the camera in a bag. Maybe thanks to living in the dark and gloomy Sweden? ;-)



Jul 01, 2014 at 10:06 AM
RogerC11
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p.1 #12 · p.1 #12 · Erratic behavior 75mm 1.8 aperture blades


Interesting. As a new user to mirrorless cameras,Im still learning a lot. Much different than dslr.


Jul 01, 2014 at 10:11 AM





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