Silly lens question - sensors

[rlw]

I know that most DSLRs use a small sensor and because of this there is a direct effect on the effective focal length of the lens; the same as going from 6x6 to 35mm - easy. So, does this apply with all lenses, specifically EF-S lenses designed for small sensor cameras? Logic says yes I must admit.

 

[boyfalldown]

I know that most DSLRs use a small sensor and because of this there is a direct effect on the effective focal length of the lens; the same as going from 6x6 to 35mm - easy. So, does this apply with all lenses, specifically EF-S lenses designed for small sensor cameras? Logic says yes I must admit.

I not 100% sure I follow the question, but what I think you're asking is does the crop factor of all small sensor affect the effective focal length of the lens, regardless of it being ef, ef-s, fx or dx. If thats the case then yes it does

 

[grahamsewelluk]

The effective focal length does not change. You crop the image in the same way that you would in photoshop.

The overall effect is that you get less of your subject (or an "effective longer lens"!) with an increase in depth of field over a full frame camera.

So a 250mm lens on an APS-C sensor will give you the same perspective as a 400mm lens on a full frame body or film camera - but with more depth of field than the 400mm lens.

This can be quite useful for sport/nature photography but not as useful for landscapes.

 

[rlw]

thanks - I hadn't considered the DoF thing which is quite interesting and requiring of more thought. Anyway, all lenses do the same thing and there is no magic, as I thought, in any of them.

 

[boyfalldown]

thanks - I hadn't considered the DoF thing which is quite interesting and requiring of more thought.

Quick and easy way of working it out is to multiple the f number by your crop factor as well to give you the equivalent f number for DoF calculations (only) on full frame

So for example, if you shot at f8 on a crop sensor camera, with a 1.6x crop, it would be the same DoF as shooting at f13 on a full frame camera (very roughly). Pros and Cons to this too

 

[rlw]

Quick and easy way of working it out is to multiple the f number by your crop factor as well to give you the equivalent f number for DoF calculations (only) on full frame

So for example, if you shot at f8 on a crop sensor camera, with a 1.6x crop, it would be the same DoF as shooting at f13 on a full frame camera (very roughly). Pros and Cons to this too

neat - so I need to be buying lenses with big apertures then - that sounds expensive