Removing warm up filter in Photoshop

[leif_goodwin8]

Does anyone know of any semi-automated way to remove the cast from an

image associated with a warm up filter? I used an 81B on some images.

I can do an ok job manually but it is a bit suck it and see and I am

never sure that I have done the best possible job. I would rather

have a more precise sequence of events based on a bit of theory.

[neil_parker]

If you have a known white highlight in the photo, you can: image>adjust>levels, (which will give you a histogram and a set of eyedroppers, use your white eye-dropper on the white highlight, that should give you real close to a white balance, you can then fine-tune it and save the setting. If you want to automate that, assuming all your frames are relatively close in color balance, make an action that applies that saved level setting. Then you can automate this action for a whole folder full ofiles via: file>automate>batch...

[sk_arts]

...that will remove all color in the light...

 

What to do, what to do... If you have a flatbed, scan the 81B in slide mode. If you have a film scanner, obtain a 81B wratten gell filter and scan it.

 

Take the scanned filter, sample the color (5x5 sampling if your especially anal).

 

Make a new layer, fill with that color, invert the layer, drop opacity to 50% change mode to "color". It's a lot of work, but if you keep an 81B on your camera at all times, you will only need to do it once. This *might* effect contrast...

 

You may want to consider ditching such minor color shifts and doing it digitally with curves. You have far more control, remember, take photos that are as flexible as possible, with as much detail as you can get. By adding a flat filter, you are basicly creating a color cast.

[rejamesuk]

Similar to Neils answer but with a tad more control.

 

image>adjust>levels

 

you'll see at the top it says - channel RGB -

click the arrow next to it to bring down a menu.

select - RED -

 

now move the arrows on the histogram to the ends of the triangle (whatever it's shape)

Now select - GREEN - from the menu and do the same.

And finally - Blue - repeat

 

Note it will look really odd until ALL CHANNELS HAVE BEEN ADJUSTED, so dont be disheartened half way through.

 

Also, you don't have to drag the arrows on the histogram yourself. when in the individual channels, just click - auto - it will auto adjust that channel only.

 

This sounds very complicated, it's really not. give it a go.