help with centring the shot/perspective module?

[u/jamariiiiiiii]

using DarkTable 5.6.0 on an Intel MacBook Pro running Sequoia 15.1

i use DarkTable to do some light edits but nothing too advanced but am trying to broaden my knowledge in the case of happenings like this.

as you can see the nexus of the lines is ever so slightly out of centre, exacerbated by the 16:9 crop i am trying to perform.

i have tried doing some rotation of the photo which haven't worked, and i saw the perspective module. i don't know how to master these and i know it won't be perfect, but an attempt has been made

thank you

[u/Nexis4Jersey]

Maybe these videos will help you video 1 , video 2 Its a tricky photo to straighten due to the tightness of it but it is possible.

[u/jamariiiiiiii → u/Nexis4Jersey]

this is what i was able to acheve

[u/Smartich0ke]

Just a matter of playing with the vertical and horizontal tilt until it looks right. A tilt shift lens is ideal.

[u/Few_Mastodon_1271]

I clipped your example, which looks like it already has some adjustments via the crop and the rotate modules?

Two alternative edits!

I wasn't sure what goal you had for this photo, so I tried two alternatives, using the duplicate manager to have the two alt versions both available.

This was an interesting exercise for me, good practice with the perspective tools.

1. Just center the line of the V vertically.

I right clicked the grid icon under the photo, and selected 5 or 7 vertical lines, so that one of the lines would be centered. (I usually have it at 15 for more closely spaced lines, but then it's hard to easily see which one is the center.)

In rotate and perspective: I moved the rotation slider to make the center of the Vs become a vertical line. I ended up with a -2.48 degree rotation.

In crop, I moved the left margin until the V was at the center line.

This was quite easy. The two sides of the V aren't at the same angle, due to the direction the camera was pointing.

~~~

2. make the two sides of the V have the same angle.

This was tricky. I first tried drawing a quadrilateral, to put corresponding columns at each side onto the left and right sides of the out-of-square rectangular shape. This failed completely -- the module got very confused. So I reset the module.

The "select the 4 corners of a rectangle to be squared up" is normally the way to do an unusually shaped subject, but I couldn't get it to work for this scene.

I used the pencil tool to draw one line that I want to become horizontal. I selected the top of two corresponding columns for the line. Then manually changing the shift and shear sliders did work. Once the line was close to horizontal, I played with the vert and horiz shift to make it look a little better. Stretching it vertically looked less compressed.

It wasn't centered, so next, I used the crop to center it. That doesn't show on this screen shot of the rotate and perspective tool, which wants to show the whole original image, including the parts out of the frame -- which is good.

I thought this would look very distorted, but it came out pretty good. It does crop off more of the original image though.

[u/Few_Mastodon_1271 → u/Few_Mastodon_1271]

version 2 final image.

[u/Few_Mastodon_1271 → u/Few_Mastodon_1271]

version 1 final image. I like this one.

[u/jamariiiiiiii → u/Few_Mastodon_1271]

this is what i was able to achieve with some practice last night