Long exposure / grey card

[John_TheProp]

I got a hold of a few sheets of welding glass and am about to play around with some long exposures. The glass is going to give me horrendous colour cast so I'm going to shoot a greycard to help with the white balance in post.

When shooting the greycard do I need to use the same shutter speed/appature/ISO or can I speed things up by opening the appature and increasing the ISO so that my exposure time is shortened (by the same number of stops)?

 

[HoppyUK]

Shoot a plain white target, in the same light as the real thing. So long as it's not blown/over-exposed it will be fine, and better than grey as there will be less noise in it. For the same reason, don't use high ISO.

 

[Lesco]

That is some question for talk basics, I didnt understand the question or the answer LOL

 

[SoDoSoPa]

I would have thought you would be fine taking a whitebalance reading from a greycard and use whatever exposure needed to take the picture.

Although i would always shoot in raw as it gives the most flexibility to sort out any colour cast in post production.

Heres a link that might help with it,

http://blog.robertstrachan.com/arch...e-lee-big-stopper-or-hitech-pro-stop-filters/

 

[Tringa]

Put the welding glass on the camera.

Point the camera at a white wall illuminated by sunlight (do it around midday rather than early or late in the day as those times may give a colour cast of their own).

Switch to live view.

Adjust the WB so the wall looks, white, rather than a deep green.

Save this WB setting as a Custom WB and use it whenever you use the welding glass.

Dave

 

[markmullen]

It might not be quite as accurate measuring your WB at a speeded up shutter speed and ISO but for most things it will be sufficient.