Dumb question.. lens for D800

Started May 16, 2012 | Discussions thread
andy bp Regular Member • Posts: 332
Re: Photography 101

Exactly - the pictures are not the same, because you now moved and now have different perspective. the focal length doesn't change the perspective, but it demands you to change it to get the same picture.

cropping a wide angle picture will not change the perspective of the picture, but it will not give you the same picture as with a true tele lens - because of perspective. so the answer to why you need different focal lengths is perspective.

Sorry, but this is simply wrong.

FL has NOTHING to do with perspective, unless your lens has the ability to warp space and time. I don't think any amount of nano coating can achieve that

Its simple really. The only (yes only) way of changing perspective is to move your position.

Have a think about it properly, and follow this thought.

Lets say I take a portrait of person (a head and shoulders with a 600mm lens). To fill the frame I need to be a good distance away. Lets say 20 meters for arguments sake. At this distance I can see a persons ears on the side of their head.

Now I stick on a 10mm lens. In order to fill the frame with head and shoulders, I need to be around 30cm inches away, so that I end up moving in around 19.7 meters to get the same framing.

Now at this distance(30cm), I struggle to see a persons ears properly (following me so far?).

So 600mm I see ears- 10 mm I dont. The crucial thing here is that I moved position.

Had I used the 10mm lens from 20 meters away, and cropped in, I would still see the ears wouldn't I. (perhaps not with the same resolution DR, ETC etc etc) but the crucial thing is I see the ears.

Seeing the ears or not is the manifestation of perspective

1) Notice that when I switch lens at 20m away there was not change.
2) when I moved in, there was a change.

Thats is really. Changing position changes pespspetive, changing FL simply does not, it just changes the crop (DOF issues aside)

Easy eh!

Andy

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