It is impossible that a 50mm f1.8 gives much more separation than 25mm f0.95 m43, it must be the lense properties that is adding something, technically they are so similar its possibly favouring the 25mm f.95 for shallow, wide-open, not the 50mm.
photographers speaking about V f.95
- Thread starter Jonathan12uiz
- Start date
It is impossible that a 50mm f1.8 gives much more separation than 25mm f0.95 m43, it must be the lense properties that is adding something, technically they are so similar its possibly favouring the 25mm f.95 for shallow, wide-open, not the 50mm.
Lucas Adamson
Well-known member
Actually, given an equivalent DOF, achieved with adjusting apertures between the 25 & 50, the longer lens will give less background separation - as in, the longer a lens's focal length, on any format, the more it will have a flattening effect on perceived scene depth.
Matthew P
Well-known member
A 50mm on a FF camera will look EXACTLY the same as a 25mm with 2x crop (ignoring the aperture difference). It's only the field of view that changes, nothing more. The 25mm isn't somehow more distorted than the 50mm.
If you put a 25mm on a FF, and a 25mm on a 2x crop, and cropped the FF 25mm picture 2x, they will also be exactly the same (assuming that the cameras were in the same position).The only difference between a 50mm on FF, and a 25mm on 2x crop, is the shallow-dof limitation, which the f.95 seems to take care of quite nicely. Seriously, the FoV is the only difference except from that, there's no magical distortion going on or anything, or bending of physics .
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Lucas Adamson
Well-known member
A 50mm on a FF camera will look EXACTLY the same as a 25mm with 2x crop (ignoring the aperture difference). It's only the field of view that changes, nothing more. The 25mm isn't somehow more distorted than the 50mm.
The only difference between a 50mm on FF, and a 25mm on 2x crop, is the shallow-dof limitation, which the f.95 seems to take care of quite nicely. Seriously, the FoV is the only difference except from that, there's no magical distortion going on or anything, or bending of physics .
I'm sorry Matthew. That's plain wrong. It's not a "magical distortion" either, but cropped 50 and uncropped 25 on m4/3 do not look the same. 50mm will be flatter perspective. Experiment if you don't believe me. Where's a cinematographer authority when you need one?
"BARRY!"
Lucas Adamson
Well-known member
For an example of what I'm talking about, look at the relationship between the pink & blue bottles in the following link:
http://en.wikipedia.org/wiki/Angle_of_view
http://en.wikipedia.org/wiki/Angle_of_view
evilken
Active member
To add to the all English lens debate, I'm siding with Lucas on this one. Matthew you are just thinking about crop factor - a 25mm lens is always a 25mm lens, you just don't get the same field of view if you use it with a smaller sensor.
Matthew P
Well-known member
It's the POSITIONAL difference that's causing the different distortion, not lens field of view. A 50mm on a FF camera, and a 25mm on a 2x crop camera, will look exactly the same if they're the same distance away from the subject. Except for DoF of course.
Lucas Adamson
Well-known member
Still wrong.
Matthew P
Well-known member
Read what the caption is at the bottom of those images in the article you linked to if you don't believe me. Still, I guess we'll wait for Barry to come and clear things up, but at least I'm not blatantly saying you're wrong, lol.
Samuel H
Major Contributor
I'll say it again:
25mm f/0.95 on a GH2 (1.9x crop in video mode) is equivalent, in terms of field of view (23° vertical, 40º horizontal) and depth of field (14cm if focusing 2m away from the camera, calculated with the usual circle of confusion), to:
* 30mm f/1.13 on APS-C
* 50mm f/1.81 on full frame
exactly the same image coming out of each system, with the same perspective and the same depth of field, if you put the adequalte ND filters in front of the lens
come play with my DoF/FoV calculator if you wish:
http://www.similaar.com/foto/dof/dof.php?f_x=1&f_r=1.778&f_mm=50&f_f=1.8&f_d=2
or you can do the math yourselves:
http://en.wikipedia.org/wiki/Depth_of_field#DOF_formulas
or you can get the cameras and just test it
edit: plus, of course:
http://xkcd.com/386/
* 30mm f/1.13 on APS-C
* 50mm f/1.81 on full frame
exactly the same image coming out of each system, with the same perspective and the same depth of field, if you put the adequalte ND filters in front of the lens
come play with my DoF/FoV calculator if you wish:
http://www.similaar.com/foto/dof/dof.php?f_x=1&f_r=1.778&f_mm=50&f_f=1.8&f_d=2
or you can do the math yourselves:
http://en.wikipedia.org/wiki/Depth_of_field#DOF_formulas
or you can get the cameras and just test it
edit: plus, of course:
http://xkcd.com/386/
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Barry_Green
Moderator
You're not gonna like the answer...
Perspective is not a property of the lens. Perspective is a property of how far away the camera is from the subject.
Therefore -- put a 25mm lens on a "2x crop" camera, and a 50mm lens on a "1.0x crop" camera, and yes, they will exhibit identical fields of view, *and* identical perspective. The only difference between them will be the shallower DOF. Which can be equalized with the f-stop. So if you used a Voigtlander 25mm f/0.95 on a GH2, and at the exact same spot used a 50mm f/1.8 on a 5D (and equalized exposure through ISO or shutter speed)... they're gonna look identical.
Barry_Green
Moderator
I know where you're coming from, but this isn't the same thing. They changed the camera distance to compensate for the focal length difference. It is the change in camera distance to the subject that is causing the perspective distortion, not the change in focal length inherently.
Comparing a "crop" sensor to a "full frame" sensor cannot be done by using just the full frame camera and moving closer.
The way you can test it is to use a GH1 or GH2 and use the "digital zoom" feature. Put a 50mm lens on the GH1, and shoot in full frame. Then put a 25mm lens on, but turn it to "digital zoom 2x". Shoot the same scene. The perspective will be identical.
Lucas Adamson
Well-known member
Yes, you're right. Actually it's even simpler. Take a camera and put a zoom lens on it and zoom in - perspective is not changed from wide, only fov. The sensor size only affects field of view also, so yeah...:embarasse I concede, hang my head in shame, and vow never to be caught off my technical cinematography guard again! :tongue:
Barry_Green
Moderator
No worries, it's all good, we're all just trying to share info here, and sometimes it's confusing. I can't tell you how many years I've been hearing people complain about the exaggerated perspective on wide-angle lenses, and trying to explain to them that it's not the lens that's doing it, it's that you're so unbelievably close to the subject...