Keystone correction is usually used to fix converging verticals in architectural shots – that’s the most obvious use for the Capture One keystone correction tools – but this vertical keystone correction isn’t the only kind you’ll need.
Keystone distortion happens when you tilt the camera relative to your subject, and this can mean horizontal tilt as well as vertical tilt. Vertical keystoning is the most obvious because it makes the tops of tall buildings appear to converge, but you can get the same effect when you photograph a horizontal subject at an angle.
Horizontal keystone distortion is not usually as obtrusive and so you don’t necessarily need to fix it, but here’s one shot where it really is a problem.
I don’t mind the vertical keystoning in this picture because it creates quite an interesting composition and emphasises the towering scale of this cathedral’s interior, but for this to work the picture needs to be perfectly straight horizontally.
This is more complicated than it appears, because the super-wide lens I was using has introduced some barrel distortion, and I’m not sure I’ve got the camera completely level either. But I think I can solve all three problems with Capture One’s distortion correction tools and reveal a couple of top tips at the same time…
01 No lens profile?
I’ve already made the tonal and color corrections this picture needs, so my next stop is the Lens tool tab. If Capture One Pro has a profile for the lens used, it will load it automatically and apply the correction. Clearly, this time it hasn’t.
Usually, this means applying a manual correction with the Distortion slider. It’s not ideal, but it does the job. Capture One Pro can analyse chromatic aberration separately, so that’s not a problem either.
But I haven’t given up on finding a lens profile yet…
02 What was your lens?
First you need to be able to identify the lens you used. If you can’t remember (I couldn’t, because I use a lot of different lenses in my work), there is a way to find out. You need to switch to the Metadata tool tab, then scroll down the list of data until you find the lens information.
You can see it here highlighted in orange in the left sidebar. It doesn’t include the make, but that’s OK because I can recognise it from the focal length and aperture values – it’s a Sigma 10-20mm f/3.5 which I must have borrowed on the day I took my shots.
03 Select a profile manually
Back in the Lens tool tab, I’ve opened the drop-down Profile menu to see what lens profiles Capture One Pro does have. And there we are – under ‘Sigma’ it lists ’10-20mm F3.5 EX DC HSM (Canon EF)’. I was using the Nikon version of this lens, which is why Capture One didn’t find the lens profile automatically, but I reckon the Canon profile is going to be close enough because it’s effectively the same lens.
• That’s my first tip, then – if Capture One Pro doesn’t find the right lens profile automatically, take a look through the list to see if you can find a close match.
