Cropping factor/multiplier factor?

[ptm]

Hi All

Can anybody tell me when is cropping factor considered or taken into considerations?
Hehe...all I know is that it's use for calculating the focal length of a lens when it's use on a dslr.
This is my understanding, please correct me if I'm wrong.
For a 28-90 mm lens, when use on a dslr, it becomes, 45 (28*1.6) - 144 (90*1.6).

 

[Bluestrike]

Hi All

Can anybody tell me when is cropping factor considered or taken into considerations?
Hehe...all I know is that it's use for calculating the focal length of a lens when it's use on a dslr.
This is my understanding, please correct me if I'm wrong.
For a 28-90 mm lens, when use on a dslr, it becomes, 45 (28*1.6) - 144 (90*1.6).

Yes it something like that. It oso known as the focal length multiplier or FLM for short.

It because of the different in sizes of the CCD/CMOS that give birth to FLM.
For more info look here
http://www.dpreview.com/learn/Glossary/Optical/Focal_length_multiplier_01.htm
Note oso that the FLM varies from brand to brand!

 

[ptm]

thanks for the link
didn't know that the perspective will be different too.
in photography sense, is this FLM good or bad, or rather what are the pros and cons?

 

[noobee]

didn't know that the perspective will be different too.

ummmm, i think the perspective remains the same.

 

[ptm]

ummmm, i think the perspective remains the same.

ooops, sorry...yes the perspective remains the same, got mixed up by "links jumping" ;p
it changes when different focal length lens are used, eg. between a 28mm and 78mm.