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07-17-2014, 05:06 AM   #1
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tamron 90 f2.8 problem?

Hi, i just bought a tamron 90. Just wondering, when i mount the lens to the camera, i noticed that the aperture blade keeps on changing, as in it opens and closes most of the time. I set my camera to aperture mode f2.8. Is that normal? Im using a pentax k-01.

Last edited by basikal_kusayang; 07-17-2014 at 05:12 AM.
07-17-2014, 05:20 AM   #2
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When shooting in liveview, the camera will close the aperture to maintain the brightness of the image on the screen. So if you point your lens at a bright light source, the aperture will close (otherwise your screen will just show everything extra bright). And when you point it at a darker area, the aperture will open. It's normal.
07-17-2014, 05:25 AM   #3
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Thank you. So does that going to damage the lens? I dont like the sound of the aperture constantly opens and closes.
07-17-2014, 05:30 AM   #4
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QuoteOriginally posted by basikal_kusayang Quote
So does that going to damage the lens?
Of course, Pentax loves to destroy lenses.. lol just kidding.
This is how the camera makes sure a) the sensor is protected from too strong light, b) the screen is dark/bright enough for you to see an image, and c) the live view actually has enough DoF for you to compose (if the lens were wide open, then you would see a lot of bokeh and not the whole scene)
But you are right, the clicking can be annoying as it can make people think that you are constantly taking photos. However, the camera will only change aperture when the light intensity changes, for example when you point from a dark to a bright area

I think all current generation Pentax cameras do this with all lenses, but it depends on the environment how noticeable it is. I think it is perfectly safe, for the camera and lens. You can configure the green or red button to be your "DoF preview" and then you will see what the scene looks with the actual aperture
If you want to avoid the clicking, you can use a manual lens or change the aperture ring away from the A position (that way, the camera won't be able to know how much to stop it down). Just don't point the camera(when in live view) at a very bright light source, like the sun, as it could potentially damage your sensor
Another thing is, that some lenses are much louder with the aperture clicks than others. It depends on materials and mechanism.
Also, make sure you are using the latest camera firmware

07-17-2014, 05:42 AM   #5
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Thank you so much guys. Yeah,i'll probably set the aperture to 2.8 on the lens. Make it less anoying. Cheers again.

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