UWA lenses Full frame vs Crop
UWA lenses Full frame vs Crop
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Discussion

The Jolly Todger

Original Poster:

2,744 posts

209 months

Monday 12th August 2013
quotequote all
As we all know the focal length of a lens doesn't change whether it is fitted to a crop sensor camera or a full frame camera (a 50mm is still a 50mm), what changes is the angle of view. So on a crop sensor camera (assume 1.5x) a 50mm lens gives an angle of view equivalent to 75mm lens fitted to a full frame camera.

As we also know, focal length affects the perspective in a photograph, longer focal lengths compressing perspective and shorter exaggerating it.

My question is specifically around ultra-wide lenses where the effect is most obvious.

I have a Nikon DX camera and the 10-24mm lens. At 10mm this gives the same angle of view as a FX camera with a lens at 15mm. My questions is does anyone own both systems and lenses capable of those (or similar) focal lengths. I would love to see a side by side comparison of the same scene from both the DX and FX systems to compare the affect focal length has on two pictures with the same field of view.

Most people talk of lenses on crop cameras and their 35mm equivalence (in terms of field of view) but no-one seems to mention the effect of the change in focal length.

MikeGTi

2,719 posts

230 months

Monday 12th August 2013
quotequote all
I think that a number of lens reviews on DP Review show the different fields of view from full frame and crop sensors.

The Jolly Todger

Original Poster:

2,744 posts

209 months

Monday 12th August 2013
quotequote all
I'm not interested in the difference in fields of view. I'm interested in the effect on the perspective (if any), different focal length lenses have on different sensor sized cameras where the fields of view are equivalent.

Edited by The Jolly Todger on Monday 12th August 11:30

Janesy B

2,625 posts

215 months

Monday 12th August 2013
quotequote all
It doesn't change, you just see a smaller portion of the image on a crop sensor.

LongQ

13,864 posts

262 months

Monday 12th August 2013
quotequote all
Try this:

http://www.cambridgeincolour.com/tutorials/camera-...

Interactive examples are provided and discussed.

For all references throughout the site just type "Perspective" into the Search option and choose whatever looks interesting from the list.

The Jolly Todger

Original Poster:

2,744 posts

209 months

Monday 12th August 2013
quotequote all
Useful link, thanks.

From that and other sources it turns out that perspective is unaffected by focal length but by distance to the subject, which for any given composition is affected by focal length.


So for a given composition, focal length affects how close you are to the subject, which affects perspective.

In my example above the 10mm on a 1.5x Crop sensor camera would give exactly the same image (ignoring DOF) as a 15mm lens on a full frame camera. However using a 50mm on both cameras but changing distance to the subject in order to create a similar image would result in a change in perspective as the ratio of distance from subject to camera and background to camera wouldn't be the same.