Did you always have Enable Profile Corrections enabled, but Adobe just added the profile, so it’s actually doing something, now, but before there was no profile, so it wasn’t? With LR 6, Adobe did add lens-profile support for this lens: Canon EF 8-15mm f/4L Fisheye USM.
I would suggest is that you leave profile corrections enabled so you get the vignetting correction but you set the Distortion slider to 0 so things are still fishy.
Then click the Setup box and choose Save New Lens Profile Defaults.
Then select a new, non-edited image, change Setup from Auto to Default, then press the Alt key, click the Set Defaults… button that reset changed to, then select Update Defaults to Current Settings, or whatever the wording is.
That sequence of operations will make LR use Distortion correction of 0 for that particular fisheye lens by default but still correct vignetting.
Thank you for your response. That's certainly the lens I use and your explanation makes sense. Unfortunately, I see no profile for the lens in my set-up. I've looked around on the web and it certainly appears that the profile should be there. I have no updates oustanding. Any ideas about why it might be missing and how I can fill the gap?
Actually cancel that. I had been exporting a folder to PT Gui and clicked on a tif file to check profiles. Now I'm on a raw file I see the profile. Thank you! It looks like you have found me the solution. I'll come back and whinge annoyingly if that turns out not to be the case!
All tickety-boo, but I can't follow your penultimate para. If you have a moment to run that by me again, I'd be most grateful.
Ok, here is another version of the instructions to make Distortion of 0 as a LR default:
Select a completely new, unadjusted RAW image from that lens, that has only an Import record in the History.
Scroll down to the Lens Corrections area.
Click the Profile tab.
Make sure the Enable Profile Corrections checkbox is enabled and that the proper lens profile is selected automatically.
Adjust the Distortion slider to 0 so the image looks fishy, again, note that Setup has changed from Auto to Custom.
Click the Setup - Custom and choose Save New Lens Profile Defaults.
Click the Setup - Custom, again, and change it to Default.
Press and hold the Alt key, and click the Set Default... button (that used to be the Reset button until Alt was pressed).
Click Update to Current Settings and confirm this is what you want to do.
That should be it. It is important that you start with a completely unadjusted photo from that lens, so that when you set the defaults at the end, you're not picking up any other of the adjustments besides changing Setup - Auto to Default.
Thank you so much for taking the time to walk me through that. I can see the 'Set Default' button you're referring to now, right at the bottom of the panel. If I complete that action will it set the default lens as the 8-15 for every image I import from that camera or will it only do so for images taken using that lens? Your comments also led me to an interesting article which I share for the sake of others - Adobe Lightroom - Customising Camera Defaults
The first group of three steps tells LR to use a new default for the fisheye lens, only.
The second group of three steps tells LR to use Default as the new Lens Corrections Setup value for all lenses. Having Default for Setup tells LR to use custom settings for any lenses that you've set them for and use Auto settings for any lens you have not.
It is important to have LC Setup = Default instead of Custom when you set the new LR Defaults, otherwise you would have those lens settings for every lens for your camera.