Focal lenght with Viltrox ef-fx2 adapter

[Honza]

 

Hello to everybody
I wonder how focal length conversion works with an adapter Viltrox ef-fx2 adapter (0.71x) mounted on Fuji X-T1. For example - if I use a Canon EF 50mm f/1.8 STM lens , what will be the real focal length and aperture number corresponding to the FF? Respectively, what kind of lens on FF would this setup correspond to?

Thanks for answering the beginner question

Edited July 28, 2021 by Honza

[mrPeter]

10 seconds googling gives you the answer from the Viltrox site:

"Viltrox EF-FX2 mount adapter is designed to allow Canon EF-mount series lenses to Fuji X-Mount mirrorless cameras. Focal length is multiplied by 0.71 based on the original (equivalent focal length = focal length x 0.71), which helps enlarge 1 level aperture"

[Honza]

Hi @mrPeter

Thanks you for answer. I found this information. It's just not clear from it, the conversion seems to apply to the aperture number as well. Then 50mm 2.0 corresponds to 35mm 1.4 on FF.

Edited July 28, 2021 by Honza

[mrPeter]

That's how I read it as well.

[jerryy]

As mrPeter is pointing out, the adapter is acting as a focal reducer, so when used with the 50mm lens, it is no longer a 50mm lens but a 35mm lens. The maximum aperture will change as well.

[Honza]

@jerryy Ok it sounds good. Does the minimum aperture value remain intact?

Edit: sorry for double post

Edited July 28, 2021 by Honza

[Honza]

@jerryy Ok it sounds good. Does the minimum aperture value remain intact? And the crop factor of the chip does not play a role in the calculation? Then it would be true that 50mm X 0.71 (converter) X 1.6 chip crop factor?

[jerryy]

https://en.wikipedia.org/wiki/Aperture

I am using this one because it covers a lot different uses of aperture.

In photography, we use f-stop for aperture, it is a ratio of how far the diaphragm is open as compared to the focal length. According to most places, including the one I linked to, minimum aperture does not use focal length for its calculation, so I am uncertain as to whether or not any given focal reducer will change the minimum aperture.

While it may seem counterintuitive, aperture is not affected by crop factor. The lens will  always present the same circle size regardless of the sensor size. And the same ratios.

If a focal reducer makes the lens circle size smaller, it will have some effect, most reducers actually give you a wider field of view, in your case, the new 35mm vs the old 50 mm, but, …, if the sensor size was already smaller than the circle the lens presented before, the new lens circle size will not matter.

Uh, depth of field goes with f-stop, so that will be affected.