Ok I'll butt in here too,
I have absolutely no formulas to back up my experience, only my results, and for me. While adding tubes certainly does allow closer focusing, it also increases the magnification,
Much the same as you would when using a handheld magnifying glass, by moving it closer or further away, more tubes pushes the lens further from the sensor, thus increasing the magnification.
An easy way to test this is to take a shot at 1:1 if your lens allows, with no tubes of a ruler, on the mm side. It should match your sensor dimensions, then add tubes. And try again,

More tubes = more magnification from my trials anyway, that's why I use bellows, it's like a variable extension tube.

My tuppence worth, for what it's worth.

Well isn't that just a cracker, seriously, just brilliant

The joy, of waiting for a 6 or 7 min exposure, plus another 6 or 7 mins dark frame and then these pop up on your screen
sheer bliss


IMGP3611ed1 by dr.shutter, on Flickr


IMGP3616ed2 by dr.shutter, on Flickr


IMGP3614ed1 by dr.shutter, on Flickr


IMGP3613ed2 by dr.shutter, on Flickr

and a little pp on this


IMGP3616ed2c1 by dr.shutter, on Flickr

Definitely not a secret, I posted the way I do it a couple of years ago,
Here is the link

https://www.pentaxuser.com/forum/topic/my-light-trails-explained--kind-of--60434

Cheers guys, i genuinely appreciate you taking the time to look and comment.
I have always been fascinated by these since I stumbled upon the idea,
It was a shot in the main gallery originally that gave me the idea, it wasnt a light trail shot, but who ever took it said they had used a light on a string to light the object, and that got me thinking
That they suggest form and depth mystifies me as they are basically flat,

Karlo and David, thanks, but i would neither know how to go about it or even what to charge

Anyway thank you again and here is a big thank you


IMGP3610ed2hslsm (1) by dr.shutter, on Flickr

And 2 that have been mirrored


IMGP3607edl2wsm1 by dr.shutter, on Flickr


IMGP3607edl2wmsm1 by dr.shutter, on Flickr

Haven't shot any light trails for a while, so i recently set it up again to see what i could get.
Here are a couple of shots
No mirroring or replicating, just basic edits.


IMGP3606ed2lsm (1) by dr.shutter, on Flickr


IMGP3610ed2lsm (1) by dr.shutter, on Flickr


IMGP3607edl2sm by dr.shutter, on Flickr

And a crop of the last one


2020-02-03_10-21-04 by dr.shutter, on Flickr

Cheers Guys, Thanks SteveF for answering the Dart question,
That pub always looks busy, but I have never been inside it. I think Bill knows it as well as it is just around the corner from the theatre.
I was disappointed that there were so many repair works going on but hopefully in the future it will mean that they are shootable.
And yep it is a bit of a walk from Guinness gate to the Samuel Beckett

A few shots from a wander along the quays
heavy pp on a couple due to repair works

Always nice when you get an epic shot


2020-01-18_12-17-43-02 by dr.shutter, on Flickr

The Dart


2020-01-18_12-01-47-02 by dr.shutter, on Flickr

Samuel Beckett Bridge


2020-01-18_12-17-52-02-01 by dr.shutter, on Flickr

St Jame's Gate Guinness brewery


2020-01-18_10-54-28-01-03 by dr.shutter, on Flickr


2020-01-18_10-54-28-01-04 by dr.shutter, on Flickr

and the original, thank heavens for pp


IMGP3091unedsm by dr.shutter, on Flickr


IMGP3130ed2sm by dr.shutter, on Flickr


IMGP3125ed2sm by dr.shutter, on Flickr

Cheers guys, This place is only an hour away from me and is definitely a spot i will be returning to hopefully with varying weather conditions to see what i can capture / create.

Haris, I stopped shooting just after the 5th shot in here, as a rather large surge left me with 2 wellies full of water