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It is possible to use an HDMI cable to extend the lead on the Pi Camera CSI-2 connection, but some lower quality HDMI cables will not work (and do not allow the camera to start up) without modifications to the Tindie connector cards https://www.tindie.com/products/freto/pi-camera-hdmi-cable-extension/. This is because some cables do not include the ground/shield connection for the 4 data pairs, and some do not include a wire for the Consumer Electronics Control (CEC) channel on pin 13.

There are 2 modifications required:

The first modification uses the overall cable screen to replace the non-existent data pair screens. To make this modification, simply use solder to bridge the 2 rectangular pads above to the "GND" caption on the right hand side of the HDMI socket. Thanks to Tindie and his blog http://petitstudio.blogspot.co.uk/2015/05/hdmi-cables-are-not-all-same.html for this modification.

The second modification uses one of the spare cores (labelled a, b, c and d) instead of the possibly non-existent Pin 13 CEC core. This modification requires a fine soldering iron and a magnifying glass to solder a wire between pin 13 on the CSI-2 flat cable connector (coincidentally connected to pin 13 on the HDMI connector) and the round pad labelled "d". Use a test meter to check that you have not created a solder bridge to pin 12 or pin 14 after making this modification. I chose the "d" pad because this is a data wire in the normal usage of HDMI.

Of course, these modifications need doing at both ends of the cable

The unmodified board, and the 2 modifications are shown below.

Modification 1
Modification 2

The HDMI pins are numbered from 19 on the left to 1 on the right in the images. The CSI-2 connector pins are numbered from 1 on the left to 15 on the right. The detailed pinout is below for reference.

CSI-2 Pin Name Purpose Tindie PCB HDMI Pin HDMI Name
1 Ground Ground Ground 11 Ground
2 CAM1_DN-0 Data Lane 0 12 TMDS Clk -
3 CAM1_DP0 Data Lane 0 10 TMDS Clk +
4 Ground Ground Ground 8 Ground
5 CAM1_DN1 Data Lane 1 9 TMDS 0 -
6 CAM1_DP1 Data Lame 1 7 TMDS 0 +
7 Ground Ground Ground 5 Ground
8 CAM1_CN MIPI Clock 6 TMDS 1 -
9 CAM1_CP MIPI Clock 4 TMDS 1 +
10 Ground Ground Ground 2 Ground
11 CAM_GPIO 3 TMDS 2 -
12 CAM_CLK 1 TMDS 2 +
13 SCL0 I2C Bus 13 CEC
14 SDA0 I2C Bus 14 Reserved
15 +3.3v 15 DDC
a 19 Hot plug
b 18 +5v
c 17 Data Shield
d 16 DDC