Jun 022010

And if it’s not the forest but only my backyard in Vienna, oh well, it’s rain nevertheless 🙂

Yesterday I told you about the latest quirk of my Tamron 17-50/28 VC lens, namely that it sometimes overexposes the first image after I have turned on the camera. This is what it looks like:

Both images have the same EXIF data. It’s 1/20s, f6.3 and ISO 200. They should look exactly the same but don’t, thus one of the values must be wrong. ISO and shutter speed are set in the camera, thus it must be the aperture setting.

This actually makes sense. Normally the lens is wide open, to make for a brighter viewfinder image. Only when I press the shutter, the lens is stopped down to the selected aperture, then the shutter opens, the image is exposed, the shutter closes, and finally the aperture opens up again. Seemingly my lens sometimes fails to react to the command to stop down. From f2.8 to f6.3, that’s two and a half stops, and this is about the amount the exposure is off.

As I said, my current strategy is to set the camera to continuous mode and make not one but two exposures. It works but is still a crutch.

The Song of the Day reflects today’s weather: “The Perfumed Forest Wet With Rain” from Abdullah Ibrahim’s 1979 album “Africa – Tears And Laughter”. YouTube has it.

  3 Responses to “1328 – The Perfumed Forest Wet With Rain”

  1. Does this only happen for the first image after the lens “rests” for a while? If so, have you tried using the depth of preview button a few times before making that first post-rest exposure? It stops the lens down, so it may help. It seems a little easier than firing off a few frames.

  2. would be difficult if your subject moves … are these kinds of things ‘normal’ for lenses ? it is not something you were mentioning prior to dropping your lens …

    i like the leaves (grape or maple?) … nice to look at while my trees are bare BUT its raining here too! >>> Gina

  3. @Kent: Good idea. No, I have not thought of it, it may help indeed. It wouldn’t help with my problem though. Sometimes I see something, react, take a picture. When I am on continuous mode, taking a second image is automatic, I’d have to concentrate to not do it. Otoh, having to remember to press DOF preview before each image is awkward.

    @Gina: well, this lens always had problems, only their nature changed 🙂

Sorry, the comment form is closed at this time.