questioning the size of efs lens

[perk61]

everyone refers to the size of crop lenes in relationto a ff lens. does that mean a ff 28mm is really showing 35mm on a crop camers? and is an efs 10mm really 10mm on a crop ? Thanks for the help. Perk

[neuroanatomist]

The 1.6x FOCVF 'crop factor' applies to the angle of view, which is related to sensor size (smaller sensor = smaller angle of view). So, a 28mm lens if used on a 1.6x crop body (Rebel, x0D, 7D) gives an angle of view equivalent to ~45mm on a full frame/film camera.


The focal lengths on EF-S lenses are 'real' focal lengths, even though those lenses cannot be mounted on FF cameras. So, the EF-S 18-55mm kit lens has an angle of view equivalent to 29-88mm lens on a FF camera. Likewise, the EF-S 10-22mm (only useable on a crop body) is equivalent to 16-35mm on FF.


Two other points to note that are frequently misunderstood about the FOVCF:


1) The crop factor is not a magnification factor. Only the field (angle) of view is affected. So, if you take a picture with a 200mm lens on FF, and then take a picture of the same subject from the same distance with the same lens on a 1.6x body, the subject will cover the exact same amount of area on the sensor, there will just be less 'stuff' around the subject on the crop sensor.


2) The crop factor also applies to aperture in terms of depth of field, assuming you are framing the subject in the same way - that's because you need to be further from the subject with the crop sensor, and subject distance affects DoF. So, the EF-S 17-55mm f/2.8 lens has the equivalent angle of view and depth of field as a 27-88mm f/4.5 lens on a FF camera.


Hope that clarifies things a bit...if not, let us know.


--John

[perk61]

wow. thanks for such a timely responce. It

[Kayaker72]

Yep....some good write ups if you want more information:


www.the-digital-picture.com/.../Field-of-View-Crop-Factor.aspx


www.dpreview.com/learn


en.wikipedia.org/.../Crop_factor


There are a ton more if you do an internet search.