lens shading

[NewYorkLion]

Hey all,

Have you folks set up the lens shading on your HPX? I'm using a j15aX8 sx12. Currently, I've got my shading set to default and I wondering what I have to gain by messing around in there. any hints?

 

[Dino]

Shoot something white that is evenly lit(use a meter and waveform), don't zoom in all the way, light level should be at an F-stop you use frequently. With a vectorscope, go to full magnification and after white balancing, you should have a centered circular dot, not an oblong or bow tie shape. Look at the various default lens files to compare.

If you see magenta and green shading errors on a monitor and something other than a small circle in the vectorscope, shade the camera manually, but write down the original settings. Only change red and blue channel shading settings, not green channel.

If you're not comfortable with the above, have a tech or DIT do it for you.

 

[NewYorkLion]

yeah, the only WFM I've got is on the panny 8 inch. No vectorscope though. Ill see if one of my tech buddies can handle it for me. Does it make a big difference?

 

[Dino]

I wouldn't do it without a vectorscope.

 

[Bassman2003]

What about the method in the manual where the camera selects the lens shading based upon the white object filling the screen?

 

[NewYorkLion]

I wouldn't do it without a vectorscope.

oh, what i meant by "does it make a big difference" was, does lens shading in general make a big difference?

 

[Dino]

I don't know the HPX500, but if it has separate lens files for different brand/model lenses, which I assume it does or recognizes lenses due to CAC circuit information from CAC lenses, then the white shading may be good.

If the camera has an auto white shading circuit, then, as long as you shoot an evenly lit white area/chart, it could adjust for white shading errors specific to that lens.

Failing the above, if it's an older non-CAC lens and is not a model listed in a lens file, then you need to check the white shading on a monitor by at least looking at a flat, evenly lit white area. If it looks pure white, edge to edge, you're probably fine. Sometimes a lens that has good white shading overall by virtue of a lens file can still be bad when in 2X extender, unless the camera has a separate white shading file for it.

An improperly white shaded lens can be very obvious in certain situations, usually flat white or gray areas of a scene. Poor white shading and chromatic aberration can ruin footage.