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Old Feb 8, 2005, 6:37 PM   #11
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BillDrew, if the teleconverter fits between the lens and the camera body, there is no vignetting. However, there is light loss through the convertor. This could be significant in low light situations.

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Old Feb 8, 2005, 6:59 PM   #12
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Panzergnome wrote:
That does a good job of illustrating the different focal lengths, and gives the number that really should be used: the field of view in degrees. That has much more meaning than saying a normal lens has a focal length of 12 inches - on an 8x10" view camera.

I'd bet that if lenses were specified in terms of their field of view, wide angle lenses would be much more popular. A 75 degree field of view is bigger than 64 degrees. BIGGER IS BETTER, the salesman told me so.

Panzergnome, I really wasn't atacking you - unless you work in the advertising department of a camera manufacturer. Then I'd like to see you locked in a room full of four-year-olds and beaten to death with happy meal containers.
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Old Feb 10, 2005, 12:40 PM   #13
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I suppose when the mfg's stop putting the zoom power as the biggest and most obvious print on both their cameras and their press releases, more buyers will think of focal length and field of vision. At this point, most are only aware that the Panasonic has 12x and the Canon only has 10x, and that's what is touted in every ad.

(BTW, I face the same problem in the auto industry with people confusing the need for torque with the need for horsepower)
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Old Feb 17, 2005, 7:20 PM   #14
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Well, while I do agree that focal length is a better term I think that the use of zoom power in terms of a multiplication factor is a necesity on the digital photography market since there is no standard especially when talking about CCD/CMOS sensor sizes. Am I right or not? My two cents.
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Old Feb 19, 2005, 8:52 AM   #15
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A multiplcation factor make sense in terms of an add-on lens: 0.45X will make a 40mm (equiv) lens behave like an 18mm. With zoom lenses, it isn't at all clear unless at least one end of the range is specified. The base focal length is very rarely mentioned in the posts here (and other places), and manufacturers put the focal length in the fine print (if at all).

The variation in sensor sizes is the reason focal lengths are stated in terms of 35mm equivalents. The same issue exists with chemical cameras: a 12 inch lens is normal for an 8x10" glass plate camera, 6 inch for a 4x5" sheet film camera, 70-90mm for a 640/120/70mm roll film camera, 50mm for 35mm sprocketed film. Since those changes occured over about 100 years, there was lots of time to get used to a different sensor size.

Zoom range could be stated in terms of multiples of sensor size and it would have meaning, and would deal with the issue of different sensor sizes very nicely. But that ain't likely to happen.
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