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Is the "spatial distortion" quality of a lens independent of the image format?


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#1 Nigel Smith

Nigel Smith
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Posted 26 February 2013 - 10:13 AM

I came across this today on the Digital Bolex webpage, which got me thinking:

 

"For instance, a 25mm in S16 has a very similar field
of view as a 50mm in S35. Even though they have a similar field of view
they do have a different look.


The look difference between S35mm and S16mm: S16 gives you roughly
twice the depth of field for any particular field of view and has none
of the critical focus issues.


Along with this greater depth of field you also get greater spatial
distortion
, meaning things in the background look further away from the
things in the foreground. So basically, when you are shooting S16
compared to shooting S35 you are trading the illusion of depth created
by an in focus / out of focus relationship, for the illusion of depth
created by the size and shape difference of foreground and background."

 

I have always considered a S35mm 50mm lens pretty much identical to a S16mm 25mm lens when shooting S16.

Is it true that it's distortion of perspective would be different?

Thanks for any opinions or advice

Nigel

 


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#2 Dom Jaeger

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Posted 26 February 2013 - 07:49 PM

Well they're different focal lengths, so yes they have different spatial distortion.

 

If you think about it, to perfectly match a S16 25mm image you'd need to use a S35 25mm lens, and crop a S16 frame out of the middle. 

 

But to get the same angle of view on different sized formats you need to use different focal lengths, which have different characteristics in terms of how they render spatial depth.


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