Photometric titration
photometric titration happens only in one condition, that one of the following substances will absorb the electromagnetic radiation.


Almost ;-)

Regardless whether you monitor a complexometric titration by eye or with the help of a spectrometer, it is a good idea to use an indicator, such as Eriochrome Black T. Then, it doesn't matter, if or how  strong the EDTA complex of the metal absorbs!

Instead, you monitor the absorption of the indicator, that is liberated from the metal-indicator complex upon addition of EDTA.