Full frame lens on a crop sensor body vs a crop frame lens on a crop sensor body.

[Felixbunny]

Me and my friend are having a debate on what is the focal length of full frame lens and crop lens on crop bodies.

His point: Crop lenses are made "x1.6" to accommodate the crop sensor. while full frame lenses are "x1"
eg.tamron 17-50 (crop lens) on a 550D (crop body) would be equivalent to 17-50mm as the lens is "calibrated" for crop bodies thus the focal length stay the same. while a tamron 28-75(FF lens) on a 550D (crop body) would be equivalent to 45-120mm due to the crop sensor multiplying the focal length by 1.6x.

My point: Its not the lens that affects the "multiplication" of the focal length, its the sensor that does.
eg. tamron 17-50 (crop lens) on a 550D (crop body) would be equivalent to 27-80mm while a tamron 28-75(FF lens) on a 550D (crop body) would be equivalent to 45-120mm due to the sensor size. While a crop lens on a ff body would cause vignetting with no change in focal length(eg. tmmy 17-50 would be 17-50) while a ff lens on a ff body would have no change in focal length too(tammy 28-75 would be 28-75).

Enlighten us?? thanks lols.

 

[tetrflare]

You are right, your friend misunderstood.

 

[spree86]

Me and my friend are having a debate on what is the focal length of full frame lens and crop lens on crop bodies.

His point: Crop lenses are made "x1.6" to accommodate the crop sensor. while full frame lenses are "x1"
eg.tamron 17-50 (crop lens) on a 550D (crop body) would be equivalent to 17-50mm as the lens is "calibrated" for crop bodies thus the focal length stay the same. while a tamron 28-75(FF lens) on a 550D (crop body) would be equivalent to 45-120mm due to the crop sensor multiplying the focal length by 1.6x.

My point: Its not the lens that affects the "multiplication" of the focal length, its the sensor that does.
eg. tamron 17-50 (crop lens) on a 550D (crop body) would be equivalent to 27-80mm while a tamron 28-75(FF lens) on a 550D (crop body) would be equivalent to 45-120mm due to the sensor size. While a crop lens on a ff body would cause vignetting with no change in focal length(eg. tmmy 17-50 would be 17-50) while a ff lens on a ff body would have no change in focal length too(tammy 28-75 would be 28-75).

Enlighten us?? thanks lols.

your point is the right one

 

[Rashkae]

you can always tell your friend to try a little online research. It's extensively documented...

 

[rhino123]

TS... you are right. Your friend is horribly wrong...

 

[kei1309]

no matter what, the focal length always remains the same.

 

[Felixbunny]

Thanks for the answers people! hahaha. Anyways then why is there FF and crop lenses? issit just that FF need "bigger" lenses to prevent vignetting?

 

[nikerocks]

I thought ff cant use crop lens?

 

[kcchew]

You can mount a crop lens on a full frame body, but you will get heavy vignetting as the lens is optimised for a smaller sensor. No problems mounting a "full frame" lens on a crop body though.

There are some exceptions for crop lens on full frame body though; the Nikon 35mm f1.8G supposedly does quite well on full frame despite being a DX lens.

 

[spree86]

I thought ff cant use crop lens?

Depends on the brand, Canon FF cannot mount EF-S lenses but no problem for Nikon. Not sure about other brands

 

[Rashkae]

I thought ff cant use crop lens?

For Sony, can! The body will auto-crop the centre "APS-C" sized section of the sensor. Or you can override it, but you'll get vignetting.

 

[Octarine]

Thanks for the answers people! hahaha. Anyways then why is there FF and crop lenses? issit just that FF need "bigger" lenses to prevent vignetting?

FF lenses are the standard, Crop sensor lenses are the exception. If you look at Canon lens line-up then you'll see more EF lenses (for FF) than EF-S lenses (for crop). All EF lenses can be used on all bodies, EF-S lenses only on crop sensor bodies. But due to price pressure in the consumer segment (crop sensor bodies) lenses for this segment were created, being lighter and smaller (since the image circle only needs to cover a small sensor).