Gamma!
Posted: Tue Oct 23, 2018 5:48 am
Guys,
It's time to come clean and 'out' with a big admission. I don't understand GAMMA. This is basic stuff, I know... No, really... I've been to various online sources to try to swot up on this and I'm now just getting more and more confused. I know you're a kindly and knowledgeable bunch here. Can any of you help?
I've put together the following understanding from the web. Some of it I may have got the wrong way round!
Gamma is the non linearity in light output that compensates for the non linear sensitivity of our eyes.
In most computer display systems and CRTs, images are fed in encoded with a gamma of about 0.45 and decoded by the device with the reciprocal gamma of 2.2.
When the gamma is 1, CRTs natively, as seen by the eye, look like they cramp to the whites with a linearly graded input. In other words, the brightness rises early in comparison with the volts in. The greys of a linear stepwedge should thus tend to look light.
Gamma correction is applied at the programme source stage.
Due to an odd bit of engineering luck, the native gamma of a CRT is 2.5 — almost the inverse of our eyes. Our eyes lift the darker greys up to look lighter than they really are. If our eyes were linear, a CRT display would look black crushed. This is the opposite of what I've said two paras above! Utterly confused!
With thanks,
Steve O
It's time to come clean and 'out' with a big admission. I don't understand GAMMA. This is basic stuff, I know... No, really... I've been to various online sources to try to swot up on this and I'm now just getting more and more confused. I know you're a kindly and knowledgeable bunch here. Can any of you help?
I've put together the following understanding from the web. Some of it I may have got the wrong way round!
Gamma is the non linearity in light output that compensates for the non linear sensitivity of our eyes.
In most computer display systems and CRTs, images are fed in encoded with a gamma of about 0.45 and decoded by the device with the reciprocal gamma of 2.2.
When the gamma is 1, CRTs natively, as seen by the eye, look like they cramp to the whites with a linearly graded input. In other words, the brightness rises early in comparison with the volts in. The greys of a linear stepwedge should thus tend to look light.
Gamma correction is applied at the programme source stage.
Due to an odd bit of engineering luck, the native gamma of a CRT is 2.5 — almost the inverse of our eyes. Our eyes lift the darker greys up to look lighter than they really are. If our eyes were linear, a CRT display would look black crushed. This is the opposite of what I've said two paras above! Utterly confused!
With thanks,
Steve O