Another newbie question about lens

[Robin Usagani]

Lets say I have the canon 10-22mm super wide angle lens. I set that to 18 mm with my 1.6x crop body. Now I take similar shot with my 18-55mm lens kit and set it to 18mm. Will I get the same perspective?

Is "wide angle" lens pretty much a low zoom lens? I understand that at 18mm you probably dont see the full wide angle look due to the cropping.

Thanks!

 

[Village Idiot]

:banghead:

 

[KmH]

The focal length is an approximation so the framing may be a little different.

In other words, assuming the same camera position, the 10-22 may be actually set set to 17.6 mm and the 18-55 set to 18.3 mm though looking at the zoom ring on both, it may look like they are both set to 18mm.

 

[Robin Usagani]

OK.. so 1.6X crop factor has a sensor size of 22.2x14.8. So if I set my 18-55mm lens kit to 18mm, since it is smaller than the width of my sensor, my picture will get distorted correct? It will produce a similar picture with 10-22mm if I set it to 18. It just that the latter lens is able to go to 10 and distort it even more?

 

[KmH]

OK.. so 1.6X crop factor has a sensor size of 22.2x14.8. So if I set my 18-55mm lens kit to 18mm, since it is smaller than the width of my sensor, my picture will get distorted correct?

No, that's not entirely correct.

The wider the field of view a lens can 'see' the more radical the shape of the various lens elements, and that is what causes distorion of the image.

It is easier (and less expensive) to correct for disortion in an 18-55 mm lens because of the longer focal ratio, than it is in a 10-20 mm lens.


Wide-angle lens - Wikipedia, the free encyclopedia

 

[Dwig]

... and as you can see, the 18-55 at 18mm is operating at its wideangle limit and produces quite a bit more geometric distortion than the 10-22 at 18 which is working well shy of its long limit.

When talking about wide angles and discussing "distortion" you need to be careful not to confuse geometric distortion (aka rectalinear distortion) with perspective alteration. The later is not truly "distortion". As already mentioned, perspective is controlled only by the relative distances of the objects in the picture.

The lens chosen has absolutely no direct affect on perspective. It only has a slight "influence" as its field of view will lure the photographer into choosing a particular shooting distance. This applies to all lenses and all uses of lenses, whether we're talking about wide angles or "portrait" lenses or whatever...