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Old Apr 11, 2006, 4:04 PM   #1
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Is there a conversion factor? Like what is the difference in my old 35 to 70mm camera lens and the lens on the FZ30. It says 12X and also 35 to 420mm, (35mm equivalent)? How does one calculate the focal length? I note in pictures take at full zoom of 12X, the focal length in the exif would be like 88.8.

Just wondering about this.

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Jerry
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Old Apr 11, 2006, 4:41 PM   #2
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According to the FZ-30 manual, the focal length is 7.4mm to 88.8mm, which translates to a 35mm to 420mm 35mm equivalent focus. So, dividing 35/7.4 (or 420/88.8 ) gives you approximately 4.73. If you know your 35mm equivalent focus, just divide it by 4.73 for the actual focal length to three places. If you know the actual focal length, multiply by 4.73 for the 35mm equivalent.


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Old Apr 11, 2006, 5:03 PM   #3
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While that seems correct to me....an exif reader like IExif will give the focal length in both terms.

http://www.opanda.com/en/iexif/index.html
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Old Apr 11, 2006, 6:36 PM   #4
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Thanks, I understand now that the ratio is approx. 4.73. Downloaded the Opanda, and I see the two different focal lengths. I quess to be an old child asking questions, why Mama, why. Why is there a different correlation in focal length between lens? Sorry, just that I worked in a technical career field (chemical plant instrumentation) and got to where I looked for answers. MM are mm to me. I just wanted to understand the difference.
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Old Apr 11, 2006, 9:55 PM   #5
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Jerry,

The difference is in the words "35mm Equivalent".

Yes, MM are mm, but in comparing cameras they can mean different things.

With our 35mm film cameras, we were aware of the fields of view of the lenses, like your 35 to 70mm lens.

With digital cameras, the sensors are very very much smaller than the 35mm film size.

And so for given fields or angles of view, the actual focal lengths are very much shorter in mm sizes, like 7.4 to 88.8mm in your FZ30.

The 35mm equivalent is a method of understanding the fields of view, compared with the familiar 35mm camera lenses.

Does that help?
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Old Apr 11, 2006, 10:41 PM   #6
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Thanks Baz, that explains the things. Appreciate your response and those of TClune and Genece. It does make more sense now.

You were are all of great help.

Jerry
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Old Apr 12, 2006, 9:44 AM   #7
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For further reference, I gave a fairly detailed summary of such conversion factoring in this previous thread...

http://www.stevesforums.com/forums/v...478858#p478858
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Old Apr 12, 2006, 2:02 PM   #8
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Thanks to all of you who have responded. This helps. So the crop factor can vary between different digital cameras as well as between the 35mm format. This is good to know.

Jerry
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