The AF-100 and Lens Distortion

B

Bassman2003

Veteran
Hello,

I do not own an AF-100 but would like to ask some usage questions to AF-100 users.

I do still photography and video production with various cameras. For my still work I use a 5D MKII. When I am shooting in a studio situation shooting people I am always aware of my focal length and how it applies to distortion and perspective. Basically keeping at 70mm and above for individuals etc... to properly represent their features.

My question is about the 2x crop with the AF-100. If I want to keep my working distance the same as the 5D I would be using a 35-50mm lens. In your experience has using a wider lens on the AF-100 this resulted in any distorted features of your subjects?

For example, If I use the Canon 24-105 lens with the 5D in the studio it is fine at 85mm. But if I shot the same image at 42mm I would not like the distortion of the subject. Now if I put that lens on the AF-100 I would be using the lens at the 42mm mark to get the 85mm look.

Would the image from the AF-100 shot at 42mm display the same or less distortion than the 5D shot at 42mm?

I am aware the AF-100 would be using just the center part of the lens but I do not know how much this affects distortion.

Thanks for your input.
 
Generally a lens's distortion is more apparent at the edges, so the AF100's cropping benefits you there. That being said, a 35mm lens is still going to have the atributes of a 35mm on any format, even if it has the FOV of a 70mm on full frame. I would say run some tests and see if the level of distortion is acceptable to you.
 
I often use the EOS 24-70, or 24-105, & even at the widest focal length have not noted any distortion.

On another note, the aperture ring built into the Kippon adapter does not work well with these lenses, unless your looking to add some vignette.
 
The facial distortion you're talking about is not caused by the focal length of the lens, it's caused by how close you are to the subject. Perspective changes based on proximity to the subject and how the lens sees everything based on your position.

A 35mm lens at five feet on an AF100 will render an image that looks exactly the same, distortion-wise and perspective-wise, as a 70mm lens on a 5D Mark II at five feet.

In fact, you can test this for yourself simply enough -- shoot a portrait at 70mm on your 5D, then stay exactly where you are, change to a 35mm, and shoot it again. Then in PhotoShop crop the 35mm frame to where it shows the same framing as the 70mm and then compare the two. You'll see that the distortion is exactly the same.
 
Hey,

Thanks for your replies and information. Make perfect sense. It is easy to equate the proper perspective to focal lengths but in reality the focal lengths give you a common working distance for certain types of shots.
 
Bassman2003 said:
Hey,

Thanks for your replies and information. Make perfect sense. It is easy to equate the proper perspective to focal lengths but in reality the focal lengths give you a common working distance for certain types of shots.
Click to expand...

Right -- and it's the working distance that creates the perspective differences.
 
Barry_Green said:
Right -- and it's the working distance that creates the perspective differences.
Click to expand...

I thought the concern was purely optical distortion, such as barrel, pincushion, or moustache.

Like most lenses, especially zooms, both the 24-70, & 24-105, suffer a bit of optical distortion, but even on the 5D, I don't find them objectionable in most circumstances, & most of this is cropped out by the AF100's m4/3 sensor.

As your concern seems more to do with FOV, I suggest you take a look at Barry's previous thread, which happens to be a sticky at the top of this forum.

http://www.dvxuser.com/V6/showthread.php?227826-Relative-Focal-Length-Angle-of-View-and-CCF-Chart

Regards,
Bern
 
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