Canon 55-250 (STM) vs Canon 100-400 (II), Kenko x1.4 Teleconverter for FF camera. Real life samples.

How to convert Canon 55-250mm (STM) lens into lens for Full frame cameras. Using Canon 5D Mark III and 5D Mark IV with Canon 55-250mm and Kenko x1.4 TC. If you are on the budget, this could be a solution.
Canon 100-400mm(MarkII)- 1570g
Canon 55-250mm STM (375g) + Kenko x1.4(TC) (111g) = 486g

0:36 Converting lens for Full Frame Camera
0:51 Kenko Teleconverter TELEPLUS HD 1.4x DGX (Don't buy Pro or old version Pro300)
https://kenkoglobal.com/product/telep...
1:11 Replacing bayonet
2:54 Lens fits back to Canon cropped sensor camera
3:18 Lens fits to full frame camera with replaced bayonet and Kenko x1.4 TC
4:58 / 7:51 Picture was taken with 55-250mm and converter/ bayonet without Kenko TC
5:09 Picture with 55-250mm + 1.4 Kenko TC
0:22 5D Mark III and 55-250mm Autofocusing
8:33 5D Mark III and 55-250mm Auto-focusing/ Manual focusing
9:35 / 14:23 5D Mark III and 55-250 Taking picture during filming
10:27 80D and 55-250mm
11:55 Magnification and zoom with Kenko TC
13:38 Focusing during taking a picture of moving object (80d, 5D Mark III)
15:30 5D Mark IV focus points (through viewfinder)
16:47 HALO 5D Mark IV +55-250 +1.4 Kenko TC
18:25 Continues Autofocusing 5D Mark IV

19:47 Canon 100-400mm (II) vs 55-250mm (STM) +1.4 Kenko TC
23:28 Canon 100-400mm (II) vs 55-250mm (STM) +1.4 Kenko TC- Focus speed
26:31 Canon 100-400mm (II) vs 55-250mm (STM) +1.4 Kenko TC - Video
28:32 Canon 100-400mm (II) vs 55-250mm (STM) + 1.4 Kenko TC - Taking pictures of people
33:03 Canon 100-400mm (II) + 1.4 Kenko TC Video
30:40 Canon 100-400mm (II) vs 55-250mm (STM) + 1.4 Kenko TC - Distance to object
34:00 Canon 100-400mm (II) vs 55-250mm (STM) + 1.4 Kenko TC - Focal distance
35:13 55-250mm (STM) + 1.4 Kenko TC Image Stabilization and Night, low light conditions
37:05 Canon 100-400mm (II) vs 55-250mm (STM) + 1.4 Kenko TC - Moon shots and Videos
38:38 Canon 80D Digital Zoom in Video
39:02 Moon Video, close up.
40:06 Canon 100-400mm (II) + 1.4 Canon TC Video
Using Canon 80D with Digital x10 Zoom. Lens 55-250mm (STM) +1.4 Kenko TC,
100-400 (II) +1.4 Canon TC,
Tamron 150-600mm G2. It didn't work with Kenko TC, can't do auto-focusing.