Question on Cropped Body Camera and Lenses

[X-Gen]

Hello, I am a newbie in DSLR, and I would like to ask for some help regarding the relationship between a cropped body camera and lenses.

Take for example, a cropped body camera like Canon 550D, and a EF-S18-135mm.
My questions are:

1. The EF-S18-135mm lens is actually not a 18-135mm lens but made to function like a 18-135mm lens on a ff camera, so that a cropped body like Canon 550D can function like a ff?

2. If a lens like EF-28-135mm is used with a Canon 550D, the lens will fucntion almost like a 44.8-216mm lens (x 1.6 times)?

Thank you.

 

[dingaroo]

The lens focal length is the same, except when you couple it with a body, crop or FF, the sensor becomes an issue.

With a crop body like Canon 550D, the Field of View is multiplied by 1.6 times, (Nikon's crop is 1.5 times), so with a lens like 18-135mm, the effective FOV is in fact between 28.8 to 216mm.

The difference between the 2 lenses (EF and EF-S) is the target camera to be used for.

Your first question is half right, half wrong. YOu know that you can't attach an EF-S lens to a FF body, but yeah, to get the range provided by the EF-S 18-135 on a FF body, the EF 28-135 is thus made available to FF owners.

Hope I'm making sense.

 

[wdEvA]

Welcome to CS.

All lens focal length are labelled with repect to 35mm film standard (Full Frame).
The 18-135mm will always be 18-135 even when mounted on crop bodies, just that your Field of View is multipled by 1.6x (regardless of EF / EF-S lenses)

 

[X-Gen]

Hi dingaroo and wdEvA. Thank you for taking time to reply. You all have helped me to clear my mind and questions about the lenses.

Cheers!

 

[Octarine]

Just to add that Canon EF-S lenses cannot be mounted on a digital full frame or film body. Canon has put a stopper there to prevent damages to the mirror. 3rd party lenses don't have this stopper. They can be mounted and used but the smaller image circle causes mechanical vignetting.

 

[X-Gen]

Just to add that Canon EF-S lenses cannot be mounted on a digital full frame or film body. Canon has put a stopper there to prevent damages to the mirror. 3rd party lenses don't have this stopper. They can be mounted and used but the smaller image circle causes mechanical vignetting.

Thanks for the info.

 

[BigFatLenses]

sorry hijack thread abit.. was browsing canon's webiste and saw this and it kinda confused me..

EF17-40mm f4L
FOV (Horizontal) = 93°~49°20'

EF-S17-55mm f2.8
FOV (Horizontal) = 68°40'~23°20'

how to interprete ah? issit that the EF-S lens FOV value has already been cropped by 1.6x?

 

[GRbenji]

sorry hijack thread abit.. was browsing canon's webiste and saw this and it kinda confused me..

EF17-40mm f4L
FOV (Horizontal) = 93°~49°20'

EF-S17-55mm f2.8
FOV (Horizontal) = 68°40'~23°20'

how to interprete ah? issit that the EF-S lens FOV value has already been cropped by 1.6x?

The FOV for EF17-40mm is calculated on a FF
The FOV for EF-S17-55mm is calculated on a Cropped Frame.

If you still remember you maths on tangent, you can calculate them.

FOV=2 x tan-1(half sensor length/focal length)

 

[BigFatLenses]

The FOV for EF17-40mm is calculated on a FF
The FOV for EF-S17-55mm is calculated on a Cropped Frame.

If you still remember you maths on tangent, you can calculate them.

FOV=2 x tan-1(half sensor length/focal length)

okok.. thanks!