I currently use this dev. version of RT:
RawTherapee_dev_5.8-3002-g4d1711412_W64_znver2_210622
and as a side remark I have had no problems with the upstarts in Windows.
The Camera based perspective correction works fine - but - I miss the Aspect correction function from ACR.
This is the image before any correction of the perspective:
And this is after 7.1 Vertical:
This is the difference shown in Photoshop:
Because the one vertical wing is in the top of the image - it has been stretched disproportionately. In ACR I would be able to counteract this effect with the Aspect facility.
Is there any way to solve this problem in RT?
There are two things to note before I explain how to reduce the stretching. The image showing the difference exaggerates the stretching because “Auto-fill” is selected, which scales the image up to avoid black borders. The other thing is that “Camera-based” perspective correction is physically accurate, so any stretching you see is supposed to happen.
If you really want to stretch or squeeze the image, there is no way to do it directly in RawTherapee. However, you can work around this by purposely entering the wrong focal length. With a long focal length, the image stretches more than it tilts. With a short focal length, the image tilts more than it stretches. So, what you can do is enter a shorter focal length and re-adjust the amount of vertical correction.
This shows the difference the focal length makes. The lens is 15mm. For the short and long focal lengths, I used 1mm and 100mm. The difference with the short one is subtle here, likely because 15mm is already very wide.
Hi Lawrence,
Right, the auto-fill function is doing its part.
I made this one with focal length 0.50! (actual FL = 30 mm). Also 0.1 Vertical, as the Focal Length slider has no effect in Camera based Perspective if everything is default. With these settings I got this result:
I think I can see an improvement. Thanks a lot for the trick.
