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Photography Question 
Bruce Lhonneux

How to use a 2x teleconverter

Hi Jim, and members.The camera is a Pentax K1000, Lens is a smc Pentax-m 1:2 50mm.When I use the teleconverter, I only have shutter speed control for the exposure meter reading, is this normal? and what do I set the aperture at.Is it the same for the 28, 55 and 200 lens.

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5/3/2006 5:44:59 PM

Christopher A. Vedros
BetterPhoto Member Since: 3/14/2005
I'm not sure what you mean by "I only have shutter speed control for the exposure meter reading".

Are you saying that with the teleconverter on, you can't control the aperture? If turning the aperture ring doesn't affect your exposure (make the needle move), then something is wrong with the teleconverter. It should maintain the mechanical connection between the lens and the camera.

There isn't one correct aperture to set your lens at. For any scene, there will be one combination of aperture and shutter speed that will give you the proper exposure (meter will be in the middle). If you open the aperture larger (move to the next lower number), then you will need to change to the next faster shutter speed. Each time you make this shift, you will see that the needle will go back to the middle, meaning you still have a proper exposure.

Large apertures (f/2.0, f/2.8) will give you very shallow depth-of-field, meaning the subject that you focus on will be sharp, but everything in front of and behind it will be blurred. Small apertures (f/16, f/22) will give you more depth-of-field, so that more of your image from front to back will be in focus.

Slow shutter speeds (1/10th second, 1/5th second) will likely result in a blurred image if your subject is moving, or your hands are shaky and you don't use a tripod. Fast shutter speeds (1/250th, 1/500) will freeze a moving subject and give you a sharp image.

You need to decide what combination of shutter speed and aperture will give you the best creative exposure. Using the teleconverter doesn't change this, it just increases the focal length of any lens that you put on it.


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5/3/2006 6:41:51 PM


BetterPhoto Member
  Using a 2X converter will decrease your aperture range by about two f stops. An f-1.7 lens will become an f-4. Unless it's a really old screw mount converter mounted on an adapter, it should have a link to the aperture. Also, the meter should be able to read the light difference when the aperture changes when you stop it down if the aperture has no link to the camera. I would probably take the camera and converter to a shop and have both checked.

Have fun and keep shooting,
Mark H.

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5/3/2006 9:45:40 PM

Bruce Lhonneux   Thanks for your help Chris and Mark, I'll get the 2x converter checked out as it's definitely faulty, going by your answers. I have no problems with the camera and lens, it's only when I added the 2x converter it turns to custard now understand the decrease in aperture when adding the converter, thanks again for your help, much appreciated. Cheers Bruce.

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5/3/2006 11:54:36 PM

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