Table 1.

Comparison of the properties of some frequently used calcium indicators. Higher dissociation constant K_d implies better temporal fidelity of the dye, at the expense of accuracy in readout of baseline calcium levels. Shorter rise time is desirable for accurate detection of action potential onset timing. Shorter decay time may allow single action potentials to be followed from higher firing rate spike trains, but longer decay times lead to better detectability of single action potentials.

Name	Kd (nM)	Rise Time	Decay Time Constant	References
Synthetic Calcium Dyes
Aequorin	104			[32]
Arsenazo III	107			[33]
Quin-2	89			[34]
Fura-2	140	< 20 ms	<40 ms	[35, 36]
Indo-1	230	< 100 ms	< 250 ms	[37, 38]
Fluo-3	390	< 10 sec	< 10 sec	[39]
Oregon Green BAPTA-1	170	< 100 ms	1–3 sec	[29, 40]
Fluo-4	345	< 80 ms	< 250 ms	[40]
Cal-520	320	<70 ms	< 800 ms	[29]
Cal-590	561	<2 ms	< 30 ms	[30]
Calcium Sensitive Genetically Encoded Proteins
GCaMP3	365	< 100 ms	< 1 sec	[31, 41]
GCaMP5G	460	< 200 ms	< 1 sec	[31, 41]
GCaMP6f	296	< 200 ms	< 1 sec	[31]
GCaMP6s	152	< 300 ms	> 3 sec	[31]
R-CaMP2	69	< 60 ms	< 600 ms	[42]