How can gravity be describe as a carried on gravitons if light is affected by gravity but no effect on gravity? if photons are emitting graviton while it going near to mass then this graviton should effect the mass the much as the graviton that object with mass emit, and we know light have no mass  so it not have an effect  on gravity. another problem I was thinking about  is that gravity may expends in the speed of light but when object is going through curve of space time and getting way for mass we may say that the gravity force it fill is weaker but if it just follow the space-time curve then it would be effected immediately, and if it result of emitting graviton then the effect would be delayed till the graviton get to the mass which would make the gravity getting weaker in the upside relation as we except because it would be more delayed the much you get a way from gravity
 A: In classical general relativity  any object with a four vector , i.e. has energy and momentum, contributes  to the curvature of space time that is gravity. Light has energy and momentum in classical electromagnetism so the classical gravitational fields are affected.
In quantum mechanics classical light emerges from photons, and photons have a four vector. In effective quantization of gravity, which is the frame where gravitons are expected as the gauge bosons of gravity, any interaction between photons and a gravitationa field happens withvirtual gravitons, so the argument of masses does not hold. There are integrals with bounds over which the integration for the probable interaction of photons with the gravitational field of massive objects is represented by virtual gravitons. Real on mass shell gravitons have not been seen, the way photons are seen, so it has no meaning to talk about graviton photon scattering.
You have to study quantum field theory to be able to really understand this.
When gravity is definitively quantized one expects that the same will hold true.
