My camera is a Nikon D610 which I used with a Sigma 12-24 wide angle lens. Can anyone recommend a software product to straighten up horizons with? I have attached an example where I have a curved lake horizon in my photograph but I don't want to destroy the sharpness of the image.
I have not used the latest version, but DxO makes a database of a combination of body and lenses to correct some problems, like chromatic aberration, etc.
They also have a program to correct wide angle lenses deformations: https://www.dxo.com/dxo-viewpoint/
It has a 30-day trial.
Here is another program. A plug in for Photoshop.
You can also use Photoshop.
Paint shop pro has some basic corrections too.
Affinity Photo has some automatic lens corrections.
And you also have Hugin (This program does so many things)
But yes, you will sacrifice some of the image data. With extreme corrections, you need to crop the image, all the stuff that does not fit in the new rectangle.
In the specific case of your image, you will be fine.
It's a lake. It does not have a horizon on this picture (which would be a transition of water to heaven or at least of water to non-water adjacent landscape) as much as it has a shoreline. The shoreline is curved.
Of course you may want to straighten the lines for artistic reasons rather than geometric ones. You will sacrifice some subpixel amount of sharpness: that's not avoidable. To make this not unnecessarily accumulative on top of other camera-internal geometric processing losses, you'll be best served starting with the RAW image and doing all geometric processing in one swoop. A number of raw processing programs can do geometric correction of both camera and lens starting from profiled parameters, but if you want to straighten a shoreline, the profiled parameters will not be sufficient.