Fuji 16mm vs FF 24mm - angle of view vs distoration

[Styp]

Hi,

 

I hope this thread will not start a shitstorm or a battle of equipment but I have this one question.

 

24mm is a very often used photojournalist lens for environmental shots but also for portraits with a 'story'.

Sometimes I struggle with the 16mm to keep distortion under control, the kind of distortion that occurs from a little unfortunate perspective.

How is the 16mm compared to a 24mm on full frame? The sensor is smaller so the angle of view is bigger, and therefore distortion is more extreme, right? This is my theory, but probably wrong.

 

There are 2 options:

24 FF vs 24mm APS (36mm) has the SAME properties distortion wise <- Angle of view is similar

24mm vs 16mm APS (24mm) has the SAME properties distortion wise <- Image is similar

 

Can anyone elaborate on that topic or give me a good advice where to read up?

 

Thanks

Styp

 

P.s. @Mod: can you fix that terrible typo in the title?

Edited July 10, 2017 by Styp

[graflex]

24mm FF versus 24mm APS-C the angle of view is not similar. The type of distortion you're finding troublesome is the result of perspective and not lens design. The 16mm on the Fuji and a 24mm on a FF camera have nearly identical angles of view. And so you're going to get the same photo (same distortion) from both if used to frame the same scene.

 

What you're seeing in the photo as distortion is entirely the result of perspective and not the lens focal length. Perspective is a function of camera placement relative to the subject and relative to the 3D distance relationships between objects in the scene. It is not a function of lens focal length -- that relationship is not causal. Lens distortion eg. barrel distortion etc. is a different issue.

 

To take the same photo a FF camera and an APS-C camera have to be in the same place -- same perspective. To then frame the same content they have to have lenses that create the same angle of view for each format, therefore a 24mm for the FF and 16mm for the APS-C (same perspective distortion).

Edited July 10, 2017 by graflex

[JonPB]

No, a 24mm lens on a 24x36mm sensor will draw the same angle of view as a 16mm lens on a 16x24mm sensor. Yes, this is a very wide lens, and it is hard to control the funkiness that results from using such a wide angle of view. I remember reading about a classic street photographer (Winogrand?) who wanted the widest possible lens, but settled on a 28mm not because it was the widest but because it was as wide as he could get with a reliably appealing drawing for his purposes. So, don't assume that just because some photogs prefer 24mm means you should, too; 28mm and 35mm are also quite useful for environmental portraiture (as can be 18mm and 21mm).

 

Without seeing what you're talking about, it is hard to tell you what you're seeing. But, you might be talking about perspective distortion or areal distortion.

 

Test: take an image that shows strong distortion of the kind you're seeing. Edit it in a program that allows you to correct for distortion. Now, add barrel distortion (or tell the program that you want to correct for pincushion even when lines at the edges are already straight). This will reduce areal distortion. If this solves your issue, then you know what it is.

 

Theory overview--

 

I think there are three kinds of distortion:

 

1 - Perspective

2 - Linear

3 - Areal

 

Perspective distortion is the result of the distance between objects and the camera. Lenses do not affect perspective distortion beyond making certain things possible or in how a particular lens facilitates the use of particular types of shots.

 

Linear distortion is usually what people mean when they're thinking of lens-related distortion. Take a picture with a flat subject along one edge of the frame; if straight lines are bent, you are seeing linear distortion.

 

Areal distortion is usually what people are referring to when they say wide lenses distort people's heads. Of course, it distorts all subjects, but we're just more attuned to the way a human head naturally looks so we're more sensitive to distortion of it. Take a picture of a regular subject (say, a round sign) in the corner of the frame; if it appears like an egg shape rather than a circle, you're seeing areal distortion.

 

Linear distortion and areal distortion are directly and inversely correlated. Eliminating linear distortion means accepting areal distortion and vice versa.

 

Thought experiment: consider a brick wall of infinite length and width. Each brick is the same size. But, if you look to one side, the bricks further away appear to be smaller (due to perspective distortion). Now, try drawing an image of a brick wall where bricks toward the edges of the frame are smaller than those in the center. The accurate result is barrel distortion. The wider the angle of view, the stronger the naturally occurring linear distortion. In order to eliminate that distortion, the bricks at the edges of the frame must be drawn larger than they actually appear. This distorts the appearance of areas, creating areal distortion.

 

In my experience, wide-angle lenses that are perfectly corrected for linear distortion can be rather ugly in some scenes due to areal distortion. Adding a hint of barrel to the image makes it look better. Older, classic lenses do this intentionally: it isn't that optical design has only recently allowed for perfect rectilinear designs but that, before the rise of internet reviews and "oh, curved line, must be bad lens" comments, lens designs balanced linear and areal distortion. (This might be important if you're looking at photos taken with 24mm lenses from the 1980s or earlier, as they weren't as strictly barrel-free as today's designs.) Fortunately, some software-correct lenses offer the best of both worlds: the native image has quite a bit of distortion, an "ideal" correction for straight lines is very easy to achieve, and the photographer is able to decide where in the middle each image should fall.

 

Hope this helps,

Jon

[BobJ]

As someone has already said, the kind of "distortion" that you are worried about is purely due to viewpoint and a rectilinear correction in the lens and is independant of sensor size or focal length. To take an identical picture from the same viewpoint as a 24mm on full frame requires about 16mm on apsc.

[Styp]

Thanks guys! Helped me a lot with understanding a few things