nickpearse wrote:
Just so it is black and white for my sake. I am shooting with a Nikon D7100 using a Sigma Fisheye 10mm 2.8 and using the Lens Profile of the Sigma 15mm 2.8mm on Lightroom.
Then the correct profile to use is the Sigma 10mm F2.8 if you want proper Vignetting correction and matching Distortion correction, but you'll need to shoot camera raw images (i.e. no JPEG lens profile). This is also why you are only seeing partial correction. As I said, "With a crop factor camera only the central crop area of the full-frame Sigma 15mm lens profile will be applied."
That said there is absolutely nothing wrong with using the Sigma 15mm lens profile with your crop factor Nikon D7100 if you are happy with the partial correction results, but you can also do this using the correct Sigma 10mm lens profile (set less than 100). There is a fisheye correction plugin called Fisheye-Hemi that works very similar in that it only applies partial correction. You're getting about the same results as Fisheye-Hemi for free using partial correction with the LR lens profile tool. That should make you happy! I suggest experimenting with both the 15mm and 10mm lens profiles and start shooting camera raw image files. Your're not realizing the camera's full capability shooting JPEGs!
In the DSC_7098 images posted none of them look very sharp (slow shutter speed?). Other than geometric correction I can't judge the posted images for "sharpness" in the corrected areas, which is the major concern. The biggest issue with rectilinear correction of fisheye images is loss of detail in areas with the most correction (edges and corners). If that were not the case people would use fisheye lenses for ALL wide-angle images and simply correct them inside LR. Sadly that's not the case and using LR's Lens Profile Distortion and other transform tools to correct fisheye images considerably softens the corrected areas (sides and corners).
Fisheye geometric distortion with some subjects is almost undetectable. So how much correction you need will vary by subject type and what the end use for the image. Any fisheye image that has correction applied will lose sharpness in the corrected areas, which may be fine for most purposes other than large prints.So it's best not to strive for 100% rectilinear correction–Just the correction needed to make the image look better.
Canon 8-15mm F4L FE on 5D MKII Full-Frame @ 15mm (No correction)
Looks good to me with no correction!
For more flexibility and better results PS's Wide Angle Adaptive filter and content aware fill tools will retain more image detail in the corrected areas. Here's the same lens and camera with an image processed in PS:
15mm Full-Frame Fisheye
LR Distortion = 50 (partial) PS Adaptive Wide Angle Filter + Content Aware Fill
The corner image detail is about the same in both of the above images at 1:1 view. Partial LR Distortion correction is good!
So what happens if I apply 100 Distortion correction to the image inside LR?
1:1 Compare View (lower-left) with LR Distortion = 100
100% LR Distortion correction of fisheye images is NOT good IMHO!