# Zoom Question



## Miaow (Feb 10, 2008)

This may be a really stupid question lol

But a couple of days ago got (well my boyfriend did and is mine to use also) a Cannon EOS 400d which has a 75-300mm zoom.

Anyway i took a pic of something using the 300mm setting which i was showing to someone who has a P&S - Being mainly used to P&S in the past with optical zoom - I was wondering how you would equate a pic taken on 300mm with an optical zoom amount on a P&S to compare it - ie X???

Thanks


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## Big Mike (Feb 10, 2008)

The standard for comparison is 35mm film.  Your camera has a 'crop factor of 1.6, so at 300mm you compare to the filed of view on 35mm of a 480mm lens.

P&S cameras also use this same comparison...you can look up the specs of most digital cameras on www.dpreview.com


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## Miaow (Feb 10, 2008)

Hmm i should add I'm blonde  - thats gone over my head a little lol
 Ok so to covert that to a optical zoom rating would it be something like 480/35?  So about x13.7?


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## Helen B (Feb 10, 2008)

The zoom ratio is simply the ratio of the longest focal length to the shortest, so a 75-300 is a 4x zoom. (300/75)

However, as a P&S usually starts out with something like a 35 mm equivalent, and you end up with a 480 mm equivalent, your calculation is about right: a P&S would have to have about a 13x zoom to have the same 'reach' as your lens at 300 mm. 

Don't expect the same zoom ratios on a camera with the size of sensor that your 400D has as on a P&S with a much smaller sensor. It is much easier to make zooms with a high zoom ratio for cameras with small sensors.

Best,
Helen


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## Miaow (Feb 11, 2008)

Thanks for the Help Helen B & Big Mike 

Most people I know (including myself till now really) are more used to hearing a zoom amount in X... rather than mm i so its good to be able to compare the 2 in a value people will understand more lol


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## Garbz (Feb 11, 2008)

yes unfortunately this doesn't tell you much about the lens other than the higher the zoom factor the less likely it is to be a quality lens.

Afterall Nikon make a 200-400mm and 28-50mm, both have a 2x zoom range but both are very different lenses.

Many P&S cameras have the mm range written on the front too. The numbers will be ludicrously small like 3-12mm or something. Multiply this by the extremely high crop factor on most P&S cameras (anything from 2-8 i've seen) and you have a basis for comparison again.


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