These two images were taken from the same spot, with the camera mounted to a hand rail using the Manfrotto Superclamp. Both images were taken at f/8, and you can notice the Panasonic GH2's tendency to underexpose with the Samyang 7.5mm f/3.5 fisheye lens, especially with the aperture stopped down beyond around f/5.6. Normally, you will want to dial in some overexposure when using this lens stopped down, and when there is high contrast in the image.
|Lumix G 7-14mm @ 7mm||Samyang 7.5mm fisheye|
Click for larger images. Both were taken at the standard 4:3 aspect ratio. As you can see, the Samyang lens gives significantly wider field of view horizontally, and even a larger vertical field of view, just as my theoretical comparison predicted.
We could also see how the images compare when the fisheye image is defished. Read about how to defish the image using the freeware Hugin here. I used the "Orthographic" lens model, which I think gives the best results with this lens. Here are the images, with the right one being defished:
|Lumix G 7-14mm @ 7mm||Samyang 7.5mm fisheye, defished|
We see that the defished fisheye image has a much wider aspect ratio, 2.4:1. That is normal, and is due to the fisheye projection model. This means that the fisheye image has a significantly wider horizontal field of view compared with the vertical field of view.
I will later be looking at the sharpness of the two lenses. But let me reveal right now that I was not so impressed with the corner sharpness of the Lumix G 7-14mm in the widest setting, even when stopped down.
This comparison verifies my calculated comparison between the two lenses: The Samyang lens gives a significantly wider field of view. On the other hand, you lose quite a bit of corner resolution due to the defish process. You could still cut off the extreme ends, and end up with a very wide near rectilinear image with an overall good quality.