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Old Jun 13, 2003, 10:17 PM   #1
Roo
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Default Focal Length Of Camera?

This is driving me nuts!

The camera is a CP995, I'm using Tiffen Lenses. The issue involves the 2X telephoto lens.

I've just read that when using a telephoto lens that the shutter speed should be equal to or greater than the lens.

Okay fine. Except that the info that comes with the lenses says that the focal length of the lens is 2X that of the focal length of the camera.

So what the heck is the focal length of the camera?
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Old Jun 13, 2003, 10:41 PM   #2
djb
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i thionk they mean 2X the focal length of the camera's lens. so if you have a camera with a lens with focal length of 40mm to 200mm then the 2x lens would make an equivalent of 80 mm to 400 mm.

dennis
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Old Jun 13, 2003, 11:39 PM   #3
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Default Re: Focal Length Of Camera?

Quote:
Originally Posted by Roo
I've just read that when using a telephoto lens that the shutter speed should be equal to or greater than the lens.
This is referring to the 35mm equivalent. For example, with ISO 100 film speed, a 300mm lens needs approximately 1/300 sec to minimize the impact of camera shaking. Similarly, a 500mm lens needs approximately 1/500 sec. The reason is quite simple. A 300mm lens has a 6X magnification of the normal lens 50mm. A blur caused by camera shake of 0.1mm on an image taken with a 50mm lens will be magnified 6 times to become 0.6mm on the image taken by a 300mm lens. While 0.1mm may not be visible on the image taken by a 50mm lens, 0.6mm will definitely be very visible. Therefore, one must use faster shutter speed to reduce this effect.

With a small digital camera, the story is a bit different. Since the sensor of virtually all consumer digital cameras is much smaller than a 35mm film (24x36mm), the size of a telephoto lens is also smaller and hence lighter. For example, a 995 with a Nikon TC-E2 gives 300mm (35mm equivalent) F5.1. The weight of this combo is still lighter than a 300mm F5 or F5.6 35mm SLR telephoto lens. Because of this weight reduction, the shutter speed does have to be 1/(focal length).

Quote:
Originally Posted by Roo
Okay fine. Except that the info that comes with the lenses says that the focal length of the lens is 2X that of the focal length of the camera.
Check the Converter Lenses section of my 995 user guide for the information.

CK
http://www.cs.mtu.edu/~shene/DigiCam
Nikon Coolpix 950/990/995/2500/4500 user guide
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Old Jun 14, 2003, 12:36 AM   #4
Roo
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OMG shene! You have excellent info there!!! Your site is bookmarked and I'll be there a lot!
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