Originally Posted by Dj Dee
Many think or just 3 think that bandwidth will do something with the MTF. The MTF is set in the blueray then 100% MTF.
Out into a projector is the part where something happen, and MTF gets lower. Also with digital projectors. But lenses are made for 1080P with digital to manage up to 100%
In CRT case, the bandwidth needed for crt with blueray is one thing, to get higher bandwidth to reach up to what blueray requires that ok . But the MTF has its limitation in the lenses not the bandwidth. This even written in the book CRT for dummies.
Here explained correct from another forum about resolution and bandwith.
In CRT it makes sense to measure MTF in both horizontal and vertical direction because they are not the same, the explanation is easy and it involves the bandwidth
As you probably know most CRTs using raster scanning scheme, that consist of several scanlines which build up the actual image.
-In vertical plane the picture only consist of the scanlines, the thickness of the scanlines should be considered constant regardless of resolution. imagine an 1 on 1 off line pattern stucture. For MTF calculations it does matter how close the lines get together, at low resolutions scanlines may fall that far apart so another scanline(s) could fit inbetween; this case is pretty similar to the screen door effect of a fixed pixel digital display. On CRT therefore the best utilization is when the scanlines are just touching eachother. In this plane, apart from the already mentioned placement of scanlines, the scattering effect of the phosphor, the gaussian distribution of the electron beam and the lens quality (resolution) that affects MTF. This also means at lower resolutions (in vertical plane) CRT can have much higher spatial resolution, just as digital displays.
-In the horizontal plane the thigs a bit different. The traveling speed of the electron beam is much higher in horizontal plane than in vertical plane (about 1000:1), in this case the speed how we can control the electron beam intensity play a significant role too along with the parameters already mentioned for the vertical plane. This control speed is actualy the analog bandwidth.
You can imagine this as a valve: it is not possible to fully open a valve from its closed position without going through a state where it is only half opened, let this time be as short as possible, but you can't eliminate it.
So in fact, we'd need infinite bandwidth on a CRT to match the horizontal MTF to the vertical MTF. But as you already quoted there are practical considerations and constraits on how high the bandwidth should/can be, but the fact is low bandwidth can severely affect MTF in horizontal direction on a CRT.
That is however a whole different story how your eyes perceive the horizontal and vertical details in the real world -because they are not the same either.