[KimDaBa] Searching for Exif

[Doug Larrick]

[Darn it, meant to send this to the list.  -Doug]

Robert L Krawitz wrote:
>>    Date: Tue, 13 Dec 2005 21:58:44 -0700
>>    From: havoc <havoc at harrisdev.com>
>>
>>    Jesper K. Pedersen wrote:
>>> Also, what would be good values for the from/to comboboxes for
>>> focal length? Are there any standard steps for this (like we have
>>> standard steps for f numbers)?
>>
>>    I'm not sure I understand the question.
>>
>> Focal length can be arbitrary -- there are no standard steps.
>> Aperture is normally specified in full, 1/2, or 1/3 stops.


It might be useful to note that, for 35mm cameras, focal lengths around
50mm are considered "normal" (maybe 40-70mm), below this range
"wide-angle," and above this range "telephoto."  I might make the
following table:

<20mm: super wide
20-40mm: wide angle
40-70mm: normal
70-150mm: short telephoto
150-300mm: telephoto

>300mm: super telephoto


Any finer gradations that that are best left to the user, IMHO.

Of course these are all for a 35mm frame.  Modern DSLRs commonly have
crop factors of 1.3, 1.5, 1.6, or 2.0, and compact cameras can have much
higher crop factors (smaller sensors).  The focal length in 35mm
equivalent, or the sensor size from which you can compute the crop
factor, is often in the EXIF data.  DPReview has a good discussion of
focal length multiplier (as they call it) for those who need it:
http://www.dpreview.com/learn/?/Glossary/Optical/Focal_Length_Multiplier_01.htm

-Doug
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