Reason of Input Lag - GPU or CPU

[ddhrubo]

What is more responsible for input lags in video games? Poor cpu or poor gpu which contributes more to the problem? Lowering the in game settings decreases input lag but by doing this where am i removing more stress from? The cpu or the gpu?
I still a noob at these things and I'm learning. I mostly game at 1280x720 resolution. I am going to upgrade my gpu very soon with a gtx 950 or equivalent. I have a core i5 3470 at this moment and looks like i am stuck with this cpu for some time to come. It is a quad core processor running at 3.2 GHz. Will it be sufficient for 720p?
I know that gpu contributes more to gaming than cpu but I was just wondering. Thanks in advance to anyone that cares to read my boring noob post and explain the facts to me.

 

[Sergeant_Sneaky]

Lowering settings reduces stress on the GPU and adds it to the CPU (If your fps is uncapped). Your CPU is perfectly capable and will be for a while yet.

 

[assassin445522]

it is most likely your GPU but normally your GPU doesn't cause your fps to change alot

 

[ddhrubo]

it is most likely your GPU but normally your GPU doesn't cause your fps to change alot

I'm sorry I didn't understand the second part. Can you explain a bit further?

 

[assassin445522]

a GPU normally wouldnt cause your fps to drop suddenly EX(I have an fx 4130 which has a low per core performance, once i turn towards a battle in battlefield 4 my fps drops by 30 because my processor cannot handle it and it maxing out its usage but then once there is an area that my CPU is not being strained like staring at a wall my fps shoots back up to 100) If you have a CPU with good per core performance(pretty much any intel gaming CPU)this changes when you get an 8 core AMD cpu though, you can OC and get no bottleneck for a very cheap price and boost the bad AMD single core speed way up so it is good and have 8 strong cores working together to complete task alot faster multiple weak cores basically equal a strong core, making up for weak single core performance

 

[assassin445522]

a GPU usually never handles a load to big unless the settings are too high, too stop a GPU bottleneck just lower settings and u have a stable FPS

 

[assassin445522]

http://www.tomshardware.com/forum/248617-29-what-bottleneck here is a better explantion(s)

 

[ddhrubo]

http://www.tomshardware.com/forum/248617-29-what-bottleneck here is a better explantion(s)

Thanks for your reply. That link helped. In my particular case, will my cpu bottleneck my gpu? I have a core i5 3470 3.2 GHz and I am getting a gtx 950 very soon. Will this combination be ok?