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Photography Question 
Irene Troy
BetterPhoto Member Since: 5/27/2004
 

Tele-extender problem


 
 
Hi - I saw this wonderful Osprey in a large pine tree and was fortunate enough to capture his image before he flew away. Luckily, the images made with my long lens alone came out great. However, when I attached my tele-extender most of those images came out with this odd haze. Can someone, please, tell me what happened and how to avoid this problem in the future? The specs: Canon 5D; Sigma 70-500mm lens with 2X extender. Conditions: warm and cloudy, but no real haze.

Thanks for the help!

Irene


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7/24/2007 3:52:02 PM

 
Christopher A. Vedros
BetterPhoto Member Since: 3/14/2005
  Was it very humid? Maybe the extender got a little fogged up when you took it out. It's happened to me, but there aren't many places more humid than NOLA.

Chris Vedros


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7/24/2007 5:39:01 PM

 
Alan N. Marcus   What you are calling haze is known as lens flare. Lens flare is present in every optical system. However, some lens systems are better than others with regard to the magnitude of the flare present.

The job of the camera lens is to project an image of the outside world. This image is focused onto the surface of the film or chip inside the camera. The job could be performed with a single thin lens. However images produced by such a simple lens are substandard. Lens makers strive to improve the image quality by using a complex design consisting of many glass elements. Light enters the camera and transverses these lenses. Each element has a shiny surface that unavoidably reflects a small percentage of light. Every ray of this reflected light becomes misdirected and eventually bathes the film/chip with misdirected light. This is the flare light we would like to avoid.

Lens makers try to avoid this misdirected light by coating the surfaces of the lens elements. The actual purpose of coating is to reduce internal reflections. Additionally the internal surfaces of the lens barrel and the insides of the camera are painted flat black and some baffling is employed. All this and more to diminish internal reflections and cut down on flare light. When you add any optical accessory you are adding more shiny surfaces and thus contributing to flare.

The Osprey is surrounded by bright sky. In this case the bright skylight has reverberated and bounced about and intermingled with the image forming rays. The flare you loathe was compounded by use of the tele-extender.

You can lessen flare by careful camera positioning and using a lens shade. Flare also results if there is dirt/oil on the front element. Sorry to report that we have not yet discovered a way to eliminate flare from an optical system.

Alan Marcus
Ammarcus@earthlink.net


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7/24/2007 7:53:21 PM

 
Irene Troy
BetterPhoto Member Since: 5/27/2004
  Thank you, Chris and Alan for your input. I did consider humidity as the culprit, but the air was really fairly dry and the lens itself did not fog and the extender appeared to be without visible fog. I did use a lens hood, but perhaps it still permitted to much light to bounce around and cause the flare. This was something that I considered when I saw the image, but because I had used the hood, I thought that it was unlikely to be flare. Now I’m wondering if you are right, Alan, and that this is simply flare made worse because of the extender. The images made without the extender show no flare, but the extender can cause more “bounce” in light, so perhaps this is the culprit. Unfortunately, in this situation there was little room in which to place the lens in another position so as to minimize the risk of flare.

BTW: does anyone know how to fix this problem post-capture in Photoshop?

Thanks again!

Irene


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7/25/2007 5:13:02 AM

 
Bob Cammarata
BetterPhoto Member Since: 7/17/2003
  Have you experienced this before with the same lens and converter?

Maybe you can duplicate the effect by testing the lens/converter at different positions and varied zoom ranges.


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7/25/2007 5:29:20 AM

 
Samuel Smith
BetterPhoto Member Since: 1/21/2004
  never thought I would see a fix.
just me irene.
just a 2 cent post from the state mental hospital.best jello in the world.


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7/25/2007 7:38:32 PM

 
Gregory LaGrange
BetterPhoto Member Since: 11/11/2003
gregorylagrange.org
  You're going to have to not have expectations that are too high with that kind of combination. Converters are only okay with zooms, and a zoom with that big a gap in it's focal range makes it worse. It's not something a lens hood can help.
You would probably notice some even if you had a picture of something with a white or very light background. You can see some of the slight fuzziness in the pine cones that are in the plane of focus, but don't have the sharpness of something in focus.
That's what happens when you use a converter with a long zoom.


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7/25/2007 10:58:26 PM

 
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