HOW TO FIX MEIKE 6.5 mm. f/2 CIRCLE CROP AND CENTER INSIDE THE FRAME

IMPORTANT: this adobe free plugin for Lightroom makes you recover the edges of RAW photos helpx.adobe.co... With the first part of the first method (pushing the lens) should be enough to fit the circle, just tested out with my Sony alpha and it works fine.
The two ways to fix Meike 6.5mm f/2 bottom circle crop and center it inside the frame. Look in the comments for more info.
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[@IsaacRC]

IMPORTANT: with this adobe free plugin for Lightroom makes you recover the edges of RAW photos helpx.adobe.com/uk/lightroom-classic/kb/canon-5d-mark-iii-images.html With the first part of the first method (pushing the lens) should be enough to fit the circle, just tested out with my Sony alpha and it works fine.

[@allonwne]

Thanks Isaac, an interesting video. This lens is said to be made for APS-C, but I notice from reviews that it appears to clip the top and bottom on APS-C. I have a project where I will print and use rectangular passe-partouts with a circular hole for presentation, so this clipping is not acceptable. I had thought of two solutions. Just using a circle in image processing software to clip back the edges until it is a complete circle (it is after all a bit more than 180 degrees), or just repairing (filling in) the missing bits in post processing.
Can you please explain the first bit of your video. Are you forcing the lens past where it should go or holding back 1/4 mm? What exactly do you mean by displacement?
I do have PTGUI, so I could use your second solution. Thanks.

[@IsaacRC]

First I tried to do a rotational displacement by putting a tiny thick spacer on the opposite side of the circle crop ( bottom side of the lens ) it was centred but lost some of the focus properties, this means that the defect on Meike 6,5mm center it's not a bad angle in relation to the focal plane (that is the sensor) it's just that the upper part of the lens is too high in relation to the sensor's center and gets out of frame. I noticed that the mount of the lens and camera has some play when mounted, specifically a 1/4 mm. needed displacement, so if pushed downwards it's possible to achieve a proper centering of the lens in relation to the sensor. But even that, when focus to minimum distance the fisheye circle diameter increase size due to "focus breathing", so crops slightly both sides. My main interest with Meike 6,5mm. besides from panorama stitching (which the cropping it's not a problem) is to study a 180º curvilinear perspective and making aesthetic photography so the cropping is a big defect for achieving them BUT as it covers more than 190º there's enough room for correction.
- PTGUI, things to consider: Ptgui 11 in difference from it's older versions (9,10) converts any fisheye distortion to "Equidistant" but Meike's distortion is more close to a "Orthographic" curved distortion so this means PTGUI 11 squish considerably the margins of the image, this is good if the quality of the image doesn't suffer because Equidistant aspect when cropped doesn't seem to lose so much field of view as the original distortion when cropped.
Also in difference from it's older versions it has the Meike 6,5mm lens profile distortion geometry info so it's very convenient to control the real geometric parameters like setting the crop to 180º and rotate the center with precision until the cropping gets out of the circle.

[@allonwne]

@@IsaacRC Wow! Thanks Isaac for that fast and very helpful answer. I will buy the lens and follow your PTGUI advice.

[@IsaacRC]

@@allonwne well this lens is astoundingly sharp by long shot compared with other lenses, that I can assure you, but maybe there's other good aps-c circular fisheye that may interest you, i'm thinking of the new Laowa 4mm that is 220º and doesn't crop even with the 16:9 video format , Izugar fisheyes, and there's more brands i can't remember. Good luck with your projects

[@allonwne]

Another one I have used that does not crop is the Yasuhara Madoka 180 Fisheye Lens for Sony E Mount. I'm not sure if it is still available. I had missed the Laowa introduction.
Following our discussion I purchased the Meike f/2. As you say it is astonishingly sharp for a fisheye, even at f/2. The image is cropped at the top and bottom on my Sony A6000, but it is a very small amount. I will need to make the circular hole in my passe-partouts very slightly smaller than the printed image anyway and that will solve the problem without any additional work.

[@IsaacRC]

​@@allonwne Yeah, sharp enough to upscale to 180 cm. diameter at its best conditions. It's not the first time that I had to deal with chinese optics manufacture flaws, glad that my tutorial help ease your work.
I made this rectilinear conversion for Lightroom of this specific lens for this specific camera (Sony APS-C), instructions of "file inventory" are from an older Panasonic GH5 version but still useful explanations : drive.google.com/open?id=1dj3QcenKjpdbbDGEBfElaCyswRtPSxnw Also a youtuber made this cool rectilinear conversion of Meike for video: ua-cam.com/video/w6r0EYwTiZo/v-deo.html